Worlds of Nanophysics (2024)

Toward a New Dimension, First Edition, Anne Marcovich and Terry Shinn. © Anne Marcovich

and Terry Shinn 2014. Published in 2014 by Oxford University Press.

In the physical sciences, research is often characterized by a relationship between metrological experimentation and theory, where the scenarios can be either complementary or tense. In NSR, theory is circ*mscribed; it is instead a descriptive science where two tandems prevail. One consists of a relation between metrological experimentation and epitaxy; the other resides in the relation between metrological investigations and simulation experimentation. Three characteristics of nanophysics will be described in this chapter. Section 2.1, “The gold rush,” documents the speedy and sometimes radical thematic shift often suddenly adopted by practitioners on discovering the possibilities of the nanophysics instrumentation revolution of the early 1980s, and the material synthesis possibilities of the following decades. The trajectories of five practitioners who became nanophysicists between 1983 and 1998 are presented. In parallel, two examples are given of a collective drift toward the extension and institutionalization of nanophysics.

Section 2.2, “Materials, research-objects, and physical phenomena,” explores the progressive transformation of the samples demanded by experimenters in the course of their research process and the efforts of epitaxiors to respond. Epitaxiors customize—tailor—substances in order to generate specific wanted properties. This is what we term “research-objects.” Research-objects are to be distinguished from the synthesis of materials (see Chapter 1), where the latter constitutes broad generic families of matter, such as fullerenes, nanowires, nanowells, and quantum dots. Though the development of a research-object is related to the synthesis of materials, it nevertheless comprises a distinct activity, consisting of a substance’s adaptation in response to experimental exigencies. The dependence relationships between experimenters and the epitaxiors who design and produce research-objects can be complicated. Exploration of two detailed case studies illustrates how the development of a research-object leads to the successive reformulation of an initial research question. This dialog between experimental design and design of research-objects is a structuring characteristic of NSR.

The third and closing section of this chapter, “Metrological experimentation and simulation-based experimentation: between difficult encounters and synergy,” examines profiles and processes of experimentation for metrology-based experimenters on the one hand, and for simulation-based experimenters on the other. It also explores collaborations between the two approaches. The temporalities of the two groups are importantly different, affecting the ways that each perceives and formulates research questions and what counts as interesting and what is valid. We then discuss the presence of shared characteristics. Simulators and metrology-based experimentation are both essentially underpinned by description where the parameter of form is of foremost analytic significance. This terrain is highly synergistic and it again substantiates the claim that in many significant ways NSR is a combinatorial science.

2.1 The Gold Rush

In 1849, news suddenly circulated that rich gold deposits had been located in the region surrounding San Francisco, and during the ensuing months and years tens of thousands of prospectors swarmed to the area in search of riches; and numerous were those who satisfied their objectives. A similar such gold rush occurred in the Yukon in the late 1890s, when masses of men immediately modified their professional trajectory and adopted a new path and perspective in response to fresh possibilities in a pioneering landscape.1

In the domain of scientific research, the massive and almost immediate rush by scientists, during the 1980s and 1990s, toward novel instrumentation (scanning tunneling microscopy—STM) and new materials (buckyballs, carbon nanotubes, the low-dimensional substances—nanowells, nanowires, and quantum dots) suggests parallels with the gold rushes of history.2 The invention of the STM in 1981 and its crowning with a Nobel Prize just five years later, in recognition of its potential as a radically new category of metrology, is in itself an amazing gold-rush-like episode. Within the span of a decade, hundreds of researchers had abandoned their previous research instruments, and often their former research questions, in favor of the new family of scanning probing device and instrument-related questions. The same gold-rush dynamics marked the syntheses of carbon nanotubes in 1992. This nanoscale material was at once regarded by countless practitioners in a sweep of numerous and diverse fields as offering the possibility to explore uncharted cognitive territories. They quit their earlier lines of investigation and rapidly adopted elements of the nanoresearch perspective that privilege single objects, research by design, control and instrument, and cognitive combinatorials.

The NSR gold rush is similarly discernible in two institutional and collective grassroots-movement initiatives. The older 1980s molecular manufacturing science, technology, and industry initiative developed by Eric K. Drexler and his Foresight Institute, founded in 1986,3 quickly recognized the cognitive potential and important early achievements of nanoscale research, and in view of establishing links with nano, the Feynman Nanotechnology Prize was set up by molecular manufacturing movement partisans in 1993; this rewarded excellence in experimentation and theory in nano investigation.4 This prize may be viewed as a kind of permanent anchor in the then unmapped and unsettled land of the nano territories. Similarly, in 1992 the Canadian chemist, Geoffrey Ozin, published a widely read, now classic text inciting scientists to engage in the adventure of developing nanostructure materials, a new domain abounding in creative possibilities. The article written by Ozin, which called for the implanting and growth of a large nanoresearch community, remained the most cited text of the prestigious journal Advanced Materials for over a decade.5 It induced a collective movement in favor of nanoresearch—a grassroots mass rush.

In this section, the gold-rush effervescence that occurred at the very outset of nanoscale research, and that often still persists today, will be documented. Attention is drawn to the speed at which the new nanometric instrumentation was adopted. In the early years, practitioners rushed to determine precisely what the instruments consisted of and how they worked, how they could be improved, and what they could do and not do. Other practitioners immediately employed the devices on just about any substance or force dynamic that came to hand. Following a similar logic, as novel nanostructured materials were synthesized, practitioners streamed to them to explore their composition or to determine their structure or properties. Each new substance generated novel expressions of materials or even new kinds of materials, so a circular synergy soon emerged. Finally, the two above-mentioned gold rush institutional/collectivist landmarks, the Feynman Prize and the Ozin project, will be discussed as stabilizing referents in what was an often turbulent moment in the early history of nanoscale science.6

James Gimzewski is a Scottish-born physicist, presently Professor of Physics at the University of California in Los Angeles. He was trained in solid-state science during the 1970s. In the mid-1980s he obtained a research position at the IBM Zurich research center, where he was attached to the extended group that had so recently developed the STM. Gimzewski at once engaged in nanoscale studies, the field that he continues to explore. Gimzewski’s swift, spontaneous, and total involvement in NSR elucidates numerous aspects (instrumentation, diversified research substances/properties, single molecules, atomic and molecular control) of the nano gold rush. The various activities of Gimzewski convey the excitement, enthusiasm, and energy that surrounded early nano and that continue to animate many practitioners even three decades later.

The research published by Gimzewski between 1977 and 1983 lay in the sphere of surface physics and related properties. Early efforts dealt with questions and substances such as synchrotron excitation of surfaces and emission of photons, and with ionization energy and anomalous basicity of arsabenzene and phosphabenzene.7 Other investigations lay in the same surface study domain—exploration of crystalline silicon for its magnetic spin and electron properties. This research dealt, through indirect observations, only with general behavior in the microscopic world; Gimzewski’s future endeavors in the nano perspective would instead focus on individual atoms and molecules, their organization in multiple materials and concomitant properties, techniques of how to manipulate molecules, and the technology of scanning probe devices and how they interact with experimental objects. Examination of publications reveals that these projects were sometimes simultaneous or alternatively interspersed, but rarely arranged into stable clusters. This suggests the excitement of early days, and it may also intimate the multiplex, intertwined internal strands of nano as a heterogeneous cognitive and technical entity.

Between 1985 and 1995 (the date at which we close this Gimzewski investigation, which will be extended to the present in Chapter 6), the entirety of the scientist’s publications focused on aspects of nano-based issues. The majority of articles investigate the original data that can be gleaned about physical surfaces and properties such as electronic, magnetic, or photon behavior, of a long, long list of substances—copper, gold, silver, selenium, silicon, graphite, etc. In effect, Gimzewski applied the new powerful STM instrument to characterize almost any substance that came to hand in a kind of “shotgun” approach!8 This is perhaps one sign of a youthful science. The task was additionally original because the STM, unlike earlier devices, allowed practitioners to focus on morphology of single objects—a revolution in its own right.9

Gimzewski similarly conducted much research on the internal operation of the STM, and more particularly on its sister device the atomic force microscope (AFM), and on how these instruments interact with the objects under study. In 1986 he published a piece reporting an investigation on the forces acting on a sample induced by STM apparatus during measurements. In 1988, two similar articles appeared, one that studied the relation between STM action and photon emission, and another that recommended technical modifications to the STM in order to obtain a more elevated photon yield.10 The scientist later proposed techniques to enable the STM to probe beneath the surface. Though he conducted less work in this area, Gimzewski’s gold rush also entailed investigation of the dynamics and morphology of single molecules—an objective that became readily available in nano, thanks to the scanning probe microscopy devices. Along the same lines, he typically researched the capability for manipulating (controlling) single molecules and atoms.11 Gimzewski’s involvement in nanoscience was further reinforced after 1992, when he turned his full attention to STM investigation of the recently synthesized nanostructure material, C60 carbon nanotubes. Between 1992 and 1995, the application of nano instrumentation to this new nanosubstance consumed most of Gimzewski’s considerable energies. The rapid response to the emerging area of nano by James Gimzewski is emblematic of the sweep and dynamics of the nanoscience gold rush. Note that he received the Feynman Nanotechnology Prize in 1997.

Christian Joachim, a French physicist based at the Centre d’Elaboration de Matériaux et d’Etudes Structurales (CEMES) in Toulouse (France), is specialized in molecular and atomic dynamical systems, which he explored mainly through theoretical calculations. From the beginning of his career, during the 1980s, Joachim’s endeavors were oriented toward exploration of the physical, chemical, mechanical, and electronic properties of atomic and molecular systems.12 This is probably what led him to the topic of the “molecular switch,”13 which had been little studied at the time, but which has now become an important theme in nanoscale research, where reversible change in a single molecule and its conformational property are of paramount interest. As we have said and as will be seen in the next case presented here, single molecules constitute a central feature in nanoscale research, and it is notable that from the beginning of the gold rush they became one of the main topics.

Joachim’s endeavors in this field revolved around simulation, which was fundamental to his early work on the correlation between single molecules, their switching properties, the STM tip, and the tunneling effect.14 Here one observes the centrality of simulation work in the gold rush to nano. Observing and imaging at the nanoscale entailed questions and reflections on the physical properties at the molecular scale and of single atoms. Probe microscopy instruments like the STM and the AFM were in themselves the subject of research. As a matter of fact, Joachim (along with James Gimzewski and Reto Schlittler, both at IBM at the time) was awarded in 1997 the Feynman Nanotechnology Prize for his work using scanning probe microscopes to manipulate molecules and for their imaging. As stated by the Foresight Institute, which awards the Feynman Nanotechnology Prize, “in this research, a key element in Dr. Joachim’s work has been his introduction of elastic scattering quantum chemistry (ESQC) theory to explain tunneling junctions between metal electrodes and molecules, now a standard for STM image calculations,” thus emphasizing, the central role of simulation in this episode.15 In 2005 Joachim was awarded the Feynman Prize for a second time for “developing theoretical tools and establishing the principles for design of a wide variety of single molecular functional nanomachines.”

In Joachim’s case, one can simultaneously observe a continuity and a break in his scientific trajectory. His interests in calculation-based questions about molecular systems preceded and prepared his total commitment to nanoscale research from the early years of the gold rush. This is visible through his increasingly extensive combination of theoretical and experimental work. It is likewise perceptible in his research on, for example, molecular conformational changes, and dynamical and reversible molecular processes whose concrete development takes the form of single-molecule devices ranging from molecular wires to switches to logic gates to wheelbarrows.

The centrality of the single molecule in nanoscale research, which constitutes one of the vital pivots of Joachim’s trajectory and of his work in nano, is also one of the structuring themes of the French physicist Gérald Dujardin’s research. Dujardin presently heads the Groupe Nanosciences Moléculaires (which is part of the Institut des Sciences Moléculaires at the University of Orsay, France), whose ambition is to conceive and build architectures at the atomic and molecular scale on surfaces that could be, in the end, susceptible to functioning as nanomachines. Dujardin began his career during the early 1980s in molecular physics in the gas phase, where he specialized in the photo-ionization of molecules detected by spectroscopy.16 Electron energy, mechanisms of desorption of a surface, and excitation resonance figure among his main topics of study17 during the period that extends until 1991–2. At that time, he was struck when reading Eigler’s article relating his achievement of “writing” the I.B.M. logo with xenon atoms (see Chapter 1), “This has been the most extraordinary event in my career,” he reports.18 It was in this period that Dujardin caught the nano gold rush fever. For him, the possibility to “seeing” individual atoms and molecules opened a completely new perspective for his own research. While in the past he had worked on millions of molecules, therefore on abstract things, molecules were now individual objects that one could see and manipulate. At first, the radical change was not in the questions asked or in the research topics he was pursuing, but in the possibility of controlling and manipulating single molecule shapes and electronic properties.19 Dujardin and his team progressively learned to control ever more parameters: the tip’s electrons’ flux, the molecule’s geometry, its environment (such as temperature), and its relations with the surface on which it is adsorbed.20 Dujardin gradually focused on two key facets of the single-molecule nano problematic: the configuration changes in one molecule,21 and the properties of the surface on which the molecule is located—for example, the question of reconstruction and rearrangement of a surface.22

While in the beginning of Dujardin’s turn from his first domain of research was perceived by him as a simple transposition of his previous work from large populations of molecules to one individual molecule, his main question evolved. His central research topic now became how to give single molecules a functionality (for example the switching property), and how to build and control nanomachines. In a way, Dujardin’s rush into the nano world changed his research paradigm.

The major discontinuity in the research trajectory of Phaedon Avouris, that involved him in the NSR gold rush, is directly connected to adoption of the STM in 1988 and research projects entirely based on the synthesis and exploration of the nanostructured material C60 carbon nanotubes, beginning in 1998. The opening years of Avouris’ career had focused on laser spectroscopy and on classical quantum surface properties—radically distant from the nano perspective. Today, Avouris is located at the Tomas J. Watson Research Center of IBM in Yorktown Heights, New York, where he directs nano-related investigations. He also holds adjunct professorships at several US universities, including the University of California in Los Angeles. For Avouris then, the introduction of nanostructured materials and their accompanying nanoproperties revolutionized his cognitive trajectory.

During the late 1970s and early 1980s he published papers on the effects of laser spectroscopy on chemical reactions linked to photo-emission, and photophysical dynamics of aromatics adsorbed on a clean AG (111) surface.23 In 1982 he turned to a different theme: namely multi-instrument investigations of physical and chemical in situ surfaces’ structure and behavior. He set out to explore the surface geometry of adsorption24 and surface energy loss.

The break occurred in 1988. Avouris continued surface science studies, but this time through experimental investigations using the STM. Recall that the STM was developed in 1981 and won the Nobel Prize in 1986, and within only two years it had already become the centerpiece of his projects. But exactly what advantage did Avouris reap using the STM that went beyond the findings he had obtained with alternative devices? Now equipped with a STM, he could identify individual atoms and their spatial relations, he could observe the surface morphology and internal structure of single molecules, and he could control the position and architectural locations of both in order to generate novel physical properties. The STM’s atom-by-atom and molecule-by-molecule grasp of surface position and forces was a far cry from Avouris’ former world of microscopic surface science, where information was often only general and based on a more collective understanding. Scores of publications along this line of enquiry punctuated the following ten years, the most novel exploring electronic surface properties.25 Such work had already marked Avouris’ full engagement with NSR, and was followed by a second layer of nano-rooted research which began in 1998.

The year of his switch to carbon nanotubes (1998) as the material basis of his research, as opposed to his previous work on non-nanostructured substances, brought Avouris a rich harvest of important findings. He was among the first to determine in detail key electronic properties of C60.26 Over the following decade, the nanoscientist concentrated all of his efforts on a combinatorial of the STM and species of fullerenes, and he is today studying the optical and optoelectronic activities of a newly synthesized group of C60. Avouris’ path in nanoresearch represents a twin intertwined gold rush—the first in the 1980s, linked to scanning probe microscopy, and the second in the 1990s, connected with the synthesis and exploration of nanostructured materials. Such radical breaks are not uncommon in NSR, yet, as we will now show, variations on gold rush trajectories also occur.

Finally, the research trajectory of Alex Zettl constitutes a variant on the nano gold rush theme. His present work in nano was long preceded by involvement in numerous different projects. The physicist’s ultimate nanoresearch orientation is the accumulation of earlier work; he came to it step by step. The pattern is not that of discontinuity and spontaneous rallying. In this respect, it contrasts with the paths of Gimzewski and Avouris. Zettl is today Director of the Condensed Matter Physics Department at the University of California at Berkeley. He is specialized in nanostructures and their properties, and in the synthesis of nanomaterials. By what circuitous path has Zettl ultimately come to nano?

Zettl is a mathematical physicist. He began his career in 1983 with research on semiconductors, studying electronic properties associated with charge–density wave transition and non-linear conductivity in Nb-Se3 semiconducting crystals.27 Zettl continued along these lines for about ten years, however accompanied by significant changes. In 1988 he discovered the STM and began to compare his mathematical results with the physical information offered by the new instrument.28 In parallel with this, Zettl directed his attention to “single crystals,” a signature of NSR, although not unique to it. The introduction of his investigations, in which single crystals comprised a key referent, was tied to the capacity of the STM to observe the relative positions and detailed morphology of individual objects. Although only intermittently, the STM subsequently played a role in parts of Zettl’s research—a low-level presence of the nano domain.

Often, with reference to single crystals and the STM, between 1989 and 1991 Zettl focused on high-critical-temperature physics. But this field quickly lost its luster for want of interesting results. During the superconducting years, Zettl also began to study the synthesis of metal materials, and this would indirectly turn him toward nano. The gold rush began for Zettl with the development of C60 carbon nanotubes. Since 1994 the quasi-totality of his research has involved nanostructured materials, where he systematically investigates property after property—electric conductance and resistance, thermal behavior, and optical features.29 Indeed, reference to nanostructured materials has become ubiquitous in all his publications—the very heart of his efforts. Moreover, consistent with nano, parts of his work revolve around qualitative features. Lastly, Zettl’s research center is committed to the development of innovative methods for the synthesis of novel materials, and notably nanotubes. Although initially only gradually moving toward nano, Zettl has finally definitely exhibited a variant gold rush dynamic.

Other elements apart from the progressive or more sudden switch of scientists toward nanoscale questions have played a role in the gold rush that we have so far described through the trajectory of practitioners. What we could call an institutional expression of the gold rush has also contributed to the enthusiasm that has propelled researchers toward the field. Among these, one can cite the Foresight Institute, founded in 1986 by Eric K. Drexler, a militant of molecular nanotechnology. The Feynman Nanotechnology Prize, established in 1993, is a child of this Institute. Grassroots movements have similarly contributed to the rush. The enthusiasm for nano, spawned in the early 1990s in favor of expending research on the synthesis of nanostructured materials, as provoked by the Canadian nanochemist Geoffrey Ozin, illustrates the impact of collective efforts on the NSR gold rush.

Drexler is an American engineer who is frequently viewed as the prophet of future NSR; his early efforts provided one of the first organized cognitive and institutional pushes in NSR.30 During his studies, in 1979, he was struck by Feynman’s provocative 1959 talk, “There is plenty of room at the bottom,” and this drove him to invest in what he later called “molecular nanotechnology.” In 1986, together with Christine Peterson, he founded the Foresight Institute “to guide emerging technologies to improve the human condition.” His main interest here was to focus efforts on “nanotechnology, the coming ability to build materials and products with atomic precision.”31 The Institute rapidly acquired an audience, and in 1993 it created the Feynman Prize, which rewards researchers whose work has most advanced the development of molecular nanotechnology. The Foresight Institute and its Feynman Prize have contributed to the nano gold rush in three important ways. Since early days, long before nano was on the official agenda, the Institute promoted both the concept and concrete research. It made nano known when few people had heard of the word. On another register, it awarded highly visible prizes for outstanding research results. Nanoscience and scientists became increasingly visible. Nano was acquiring its lettres de noblesse. Finally, and perhaps of foremost importance, by selecting specific domains of research for prizes, the Foresight Institute has progressively affected the themes and analytic tools of NSR. It has decidedly oriented the emergence and evolution of research topics. The Institute and the Prize have notably encouraged research in four directions: (1) biology-related work, (2) the themes of single molecules, (3) control and switching, and (4) metrological and simulation instrumentation. The laureates of the Prize have frequently emerged as leaders in the diversity of domains that comprise NSR.

The nano gold rush also benefited from grassroots movements. The efforts of Geoffrey A. Ozin illustrate that dynamics. In 1992 this nanochemist published what immediately became a classic article on innovative nanomaterials in the landmark journal, Advanced Materials. For over a decade “Nanochemistry: Synthesis in diminishing dimensions” remained the journal’s most cited article.32 It proved highly influential, as attested by the fact that it had been cited over one thousand times by 2012. Ozin, perhaps more than any other single nanochemist, became identified with the growth of the field.

Geoffrey A. Ozin studied at King’s College, London and Oriel College, Oxford University. He is now Professor of Chemistry at the University of Toronto and a Founding Fellow of the Nanoscience Team at the Canadian Institute for Advanced Research. He is considered to be one of the fathers of nanochemistry. His research includes studies of new classes of nanomaterials, photonic crystals and, most recently, nanomachines. In fact it is not solely the idea, the technicity, and the orientation toward mastering and creating nanomaterials in a very controlled way that Ozin was introducing in his article to the chemistry and materials science communities. It was also the crucial position of these domains of research, which now had the tools and the research horizons to become central in the nanoscience communities, because they could provide laboratories in physics, in chemistry, and in biology with these nano-tailored materials. In all of his efforts, Ozin clearly capitalized on the 1992 radical-material’s revolution, sparked by Iijima’s synthesis of C60 carbon nanotubes (see Chapter 1); and with his characteristic enthusiasm, Ozin extended the gold rush a step beyond.33

2.2 Materials, Research-Objects, and Physical Phenomena

In this section of the chapter, we focus on what we term “research-objects,” and more specifically on their particularities in the NSR synergistic system of cognition. What is intended by the term research-object? We draw attention to a crucial distinction between materials and research-objects. For our purposes, in NSR, a material is a large family of artificial substances that are in general used in the composition of downstream commercial or research components. There exist many families of materials, such as fullerenes or semiconductors. The synthesis, production, and use of a material entail considerable specialized research, the development of fabrication routines and product standardization. By research-objects we mean specifically tailored substances (sometimes one of a kind), derived from one or several families of nanostructured materials, intended to be a terrain for the exploration of particular physical properties. Research-objects are designed by metrological experimenters in order to address often well-defined questions in the context of a particular project and even a specific experiment. The work of materializing the research-object demanded by experimenters is often undertaken by nanopractitioners referred to as “epitaxiors” (see Chapter 1), whose specialty consists of building tailored substances. One example of a research-object that has been designed for a specific research project and developed from the generic III–V family of nanostructured thin-film semiconductors is a semiconductor quantum dot composed of gallium and arsenic, located in a specially configured aluminum substrate used for research on optical radiative and propagation properties. Here the original synthesized material is the generic zero-dimensional quantum dot that has been tailored to satisfy a specific research goal.

Here we explore the centrality of research-objects in metrological experimentation and analyze their sometimes complex and precarious position located between epitaxiors, who design and make them, and metrology-based experimenters, who insist on designing them. Research-objects thus lie between experimenters and epitaxiors, and they are sometimes shared by them and at other times a terrain of dispute lies between them. It is not infrequent that stubborn silence persists between epitaxiors, who are themselves acknowledged specialists having their own established market, and experimenters. But dialog can also be abundant. Such dialog is seen in many quarters as essential because it allows elasticity in the process of research. As scientists gain understanding in the course of their experiments, they request modifications from epitaxiors, and the resulting new research-object yields an upward spiral of knowledge.

Conversely, the producers of research-objects may themselves modify their materials, and with this they sometimes convince experimenters to redirect their questions or their experimental set-up in order to explore the new object. This constitutes a dynamical process of cognition/object dialog that is one methodological signature of NSR. This dynamic will now be described for two research teams: one that explores photoluminescent emission and propagation in quantum dots, and the other which works on optical and acoustical wave propagation in nanocavities.

2.2.1 The photoluminescence case study

The case we now describe identifies some cognitive, material, and instrumental factors that accompanied the trajectory of a research group from classical optics to nanoscale research in photoluminescence, where relations between epitaxy and experimentation figure centrally. Photoluminescence is a process in which a substance absorbs photons (electromagnetic radiation) and then re-radiates them. The early research of the team director, Roger Grousson, focused on the optical superposing of images for storage purposes and on hologram optics, during the late 1970s and 1980s. Grousson’s team is part of the Institut des Nanosciences de Paris, founded in 2005.34 This institute is in part a reformatting and assembly of previous laboratories, principally the Groupe de Physique des Solides, which has functioned since the 1970s. In 1993 Grousson and his team began to publish abundantly on optical phenomena in nanoscale objects. Three factors made this transformation possible: (1) The invention and availability of picosecond lasers, and intra-laboratory construction of a high-performance wave-guide, permitted the exploration of photon dynamics of a new sort where quantum phenomena can be explored. (2) A large well-equipped epitaxy laboratory, the Laboratoire de Photonique et de Nanostructures (LPN Marcoussis-France), specialized in three to five semiconductors was developed which suddenly gave access to low-dimensional materials in the form of the synthesis of three to five substances; the objects studied by the team were quantum wells (two-dimensional substances), which had existed for almost two decades but were not easy to acquire locally. (3) Finally, the recent metrological and analytic centrality of excitons as a topic of study in photoluminescent processes became increasingly powerful topics of research.35 The combination of these three elements spelled the way to nanoscale research for Roger Grousson’s team.36 Viewed retrospectively, the study of photoluminescence has indeed constituted an important research focus in single nano-objects. In this description of work, the term “single nano-object” refers to the investigation of a single crystal, be it in the form of a 2-d nanowell, a 1-d nanowire, or a 0-d quantum dot. This capacity to conduct research on a single nanostructured crystal distinguishes NSR from most previous science. The “single nano-object” is a physical entity and beyond this it represents a pivotal concept of nanoscale research-object at large. In the first stage of their nano investigations (1993–6), the team improved its technique for the study of single nano-objects (here quantum wells) in the framework of the examination of photon excitation (absorption index) and emission, and taking into consideration the limits of nanowells and possibilities of alternative materials (nanowires).37 Nanowires are one-dimensional materials. They began to become objects of research in 1993 with five publications, rising to 26 publications in 1995 and to 94 in 1997. The team published its first article that year and thus count among the pioneers of this research area. The decision to move from wells (two-dimensional material) to wires (one-dimensional material) was related to the investigation of single nano-objects under certain technical conditions, as in the case of wave-guides. In addition, wires also yield more precise information on excitons. As just indicated, at this time nanowires were a novel rarity and quite difficult for nano experimenter physicists to acquire. The local network of epitaxy acquisition that had provided the quantum wells did not synthesize the required sort of wires. The desired wire had to be made of a particular material (GaAs and AlAs), having a specific shape needed for the prospective research. The shape of the wire took the form of a V, and this configuration has subsequently had an unintended impact on future research. But for the time being, experimenters lacked a supply network. A recently created large, well-equipped, and highly competent national epitaxy center (the Laboratoire de Photonique et de Nanostructures), headed by a colleague, could in fact have synthesized the wanted sample. Grousson’s team was indeed associated with this epitaxy network. The fact that the epitaxy lab failed to respond positively to this request shows the extreme specialization of epitaxy work, and the huge inertia that governs many activities.

At that point, the team undertook a literature search for articles on nanowires. They discovered only three epitaxy groups that could provide the specific type of nanowire they needed for their single nano-object photon luminescence work: one team in Switzerland, one in England, and one in Japan. From the Swiss, they received no reply; the English epitaxy team refused to provide wires because it was conducting its own experiments; the Japanese sent samples within a week (the Electron Devices Division, Electrotechnical Laboratory, Tsukuba Japan). This episode exemplifies the dependence relations between experimenters and epitaxiors. Had there been no answer from any epitaxior, the project could well have foundered. This is not to suggest that nanoscale research is dictated by epitaxy, but it does demonstrate that epitaxy constitutes a serious limiting condition. In the case of Grousson’s team and the Japanese, their initial dealing evolved into a long-lasting interaction. This Japanese team is the provider of nanowires for other groups, like the Laboratory of Theoretical Physics of Nanosystems in the Ecole Polytechnique in Lausanne (Switzerland).38 The Japanese team is also engaged in transistor-related epitaxy.39

The sample provided by the Japanese epitaxiors, Wang and Ogura, was made by etching V-shaped parallel lines into an aluminum (Al) flat substrate and then filling the bottom of the V with a gallium arsenic nanowire (GaAs). Exploring a single nanowire, Grousson’s team could accelerate its study of electro-photon luminescence dynamics.40 The team soon observed the presence of defects in the nanowire, and in a discussion with the epitaxiors, Wang and Ogura’s team, it was discovered that these defects were in effect quantum dots.41 The observed irregularities corresponded with different light wavelengths, which are markers of quantum dots (see Chapter 1). Grousson then requested that the Japanese team produce quantum dots of different tailored sizes encapsulated in V-shaped nanowires—an instantiation of “research-objects,” or otherwise stated, “objects by design.” As shown in Figure 2.1, the highly sophisticated laser excitation system developed by Grousson allowed the team to stimulate a single nanodot in a cluster of dots which possessed a different signature because of their different size. This yields exceptionally rich information on processes of photon emission (see the schematic of photoluminescence in Figure 2.2). One can count over 12,300 published articles dealing with quantum dots and photoluminescence between 1997 and 2012.

For some, the environment (the aluminum substrate) of the nanowires and the quantum dots became a subject for study. Here the question was to identify the quantity of luminosity issuing from the quantum wire or dot, and the amount of luminosity associated with the shape of the substrate. First of all, epitaxiors displaced the nanowire from the bottom of the V to its wall, and secondly they developed samples with different spacing widths between the apex of the Vs. Some samples had a relatively broad horizontal surface between the apex of two Vs, some others had such a small bridge that two adjoining Vs formed a W shape. Wang came to Paris with his samples in order to study the effect of these modifications on light propagation with Grousson’s team’s specialized instrument set-up. In important respects, interactions between experimenters and epitaxiors constitute a kind of collaboration. This work led the experimenters to focus more definitely and clearly on the contribution to luminosity generated by photon excitation and environment-produced effects. By separating these two components, it became possible to identify the precise consequences of strictly photon-based dynamics. This reinforced the part of Grousson’s team associated with propagation. For the Japanese epitaxiors, it provided useful information about substrates and active low-dimensional objects, and thus enhanced the capability of control over the potential relations between a tailored object and the effects that one can generate using it.42

In this episode, one can observe four types of interaction between epitaxiors and metrology experimenters. The first category may be termed “demand/supply.” Grousson’s team initiated a search for a highly specific sample, tailored to correspond with a particular experimentation project; and the Japanese supplied an object they had already developed. Interaction 2 involved a surprising observation of the existing sample and a request to the epitaxy team for it to adjust its object accordingly. This constitutes an “observation/adjustment” relationship. This second category of interaction is a balanced interaction, as opposed to the first category, which is experimenter driven. The third category of interaction is one in which a prolonged normalized exchange of suggestions and reactions on both sides routinely occurs. One observes a flow between experimenters and epitaxiors. Contrary to the first two exchanges, this is a stable, long-term collaboration. In the fourth interaction, experimenters and epitaxiors became interested, for different reasons, in the impact of the nanomaterial environment on physical effects. The nanophysicists’ interests lay in identifying and understanding the contributions of exciton decay and electromagnetic features to the luminosity of their system. The Japanese epitaxiors were interested in developing mastery of their product. This reflects this team’s occasional involvement in the advance of technological applications, such as transistors.

These different types of interaction are emblematic of nanoscale research for at least two reasons. (1) As explained in Chapter 1, NSR is a combinatorial science. Combinatorials can, as in this case, rely on the high level of technical skill—here epitaxy on the one hand, and on the other, the sophisticated experimental set of devices and procedures of Grousson’s team which make scientists of the two groups dependent on each other. (2) As will be seen throughout the chapters of this book, NSR is a descriptive science. Here, as in the majority of projects, the idea is to master a series of phenomena in order to better observe and describe them. The interactions between the two teams of the episode related here gradually tailored the object on which they were working in order to generate an increasing number and variety of properties. In this sense, this example reveals important aspects of the descriptivism that characterizes NSR.

2.2.2 The nanocavity case study

We will now present a second and even more complex instance of interaction between metrological experimentation and epitaxy. In this episode, a triangular relationship develops. Two research specialties, one in optics and the other in acoustics, are involved where epitaxy serves the independent requirements of each, and at the same time, constitutes the junction that meaningfully links the two specialties to each other. The link is such that both research domains benefit individually and in common. In the one instance, the development of a new research-object permits the transformation of a theoretical perspective into a concrete research project.43 In the other instance, the introduction of the shared object allowed the concrete generation of a new range of physical phenomena that had long been blocked by the absence of the appropriate substance.

Bernard Jusserand is a physicist specialized in optics, presently working at the Institut des Nanosciences de Paris (INSP). He predominantly uses Raman light-scattering techniques to explore photons and phonon propagation (half of his 162 publications are associated with Raman spectroscopy). His research has focused on a variety of nanomaterials, such as quantum wells, nanowires, and micro- and nanocavities. In line with this, he has developed a concern for epitaxy techniques—their possibilities and limits. He has acquired considerable knowledge in this domain. One of his doctoral students, Aristide Lemaître, working at the Laboratoire de Photonique et de Nanostructures (LPN), was to become a specialist in epitaxy, and as will be seen below, came to play a pivotal role in this story. Compared with most other practitioners in nanoscale research that we investigated in our study, Jusserand’s profile is particularly rich because it extends to such a large number of materials, research questions, and diversified but connected domains of investigation. In particular, it seems that few nanophysicists who work in optics exhibit at the same time such a sustained interest in phonons. Between the late 1980s and c.2000, Jusserand explored some of the physical properties of these materials. Raman spectroscopy also allowed him to generate sonic waves at extremely high frequencies—terahertz. In contrast with this, over this period, the technique of sound pumping was limited to gigahertz. Attainment of ultra-high frequency could only be achieved in relatively low-complexity conditions, which limited the richness of results. In this situation, the possibility of constructing analogies between acoustical waves and optical waves was compromised. Jusserand consequently oscillated between pursuing or abandoning this important topic. He nevertheless remained interested in the subject, but was unable to see how to advance in these investigations.

The second physicist relevant to this case study is Bernard Perrin, who is specialized in acoustics. His research focuses on attenuation of acoustical waves in metallic super-lattices. In 2002, in the context of a scientific meeting, he discussed his research with Jusserand, alluding to the study of elastic properties of extra-thin materials and the need to generate ultra-high frequencies for the exploration of fundamental problems in physics, and notably in his domain of the propagation of acoustic waves. In well-organized materials like crystals, waves propagate well. In contrast to this, in less well-structured materials, above a certain frequency, they exhibit localized behavior. He then wanted to examine the gap between wave propagation and localized waves. At the time, being limited to gigahertz by his instruments, a pump-probe pico laser, and by the materials, Perrin was unable to generate the terahertz waves that were essential to his experiments. For this, he desperately required a new research-material. In the same way that Jusserand was interested in the connection between sound and light, Perrin’s attention lay in the relations between sound and heat; the latter exhibiting the same nature of vibrations as sound. The complexity of their common project constituted simultaneous stimulus for further development in their own particular spheres, including heat and theory on wave propagation for Perrin and, as indicated above, convergence between light and sound for Jusserand. Perrin’s research problem drew Jusserand’s attention. They met and perceived that they could collaborate on their shared interest in vibration phenomena. Each scientist confronted his specific research problem, but found sufficient terrain to find advantage in working together. Perrin’s major difficulty lay in the lack of access to research-objects tailored to his needs.

There were two problems: Perrin was using material samples that had been created for magnetism-oriented research, for example, the manufacture of reading heads, and which were inappropriate for his acoustical studies. The second problem was the silence, or rejection that he encountered when he asked for samples from epitaxy groups like the Institut d’Electronique Fondamentale (Strasbourg) and the Laboratoire d’Electronique du Poitou. Up to this point, Perrin had worked with metal-based samples, which he saw as blocking his research: in order to advance, he perceived a necessity for three to five semiconductor materials. Perrin’s difficulty demonstrates the requirement to be part of an epitaxy network, to be able to identify people who share the same interest or to locate teams that have already synthesized precisely those materials being requested. In the absence of properly designed and synthesized materials, NSR is quite simply unthinkable. Materials-by-design are an insurmountable characteristic of nanoresearch.

Each of the two experimenters perceived benefits in collaboration: Perrin could get from Jusserand access to research-objects and to his knowledge of these materials, and also to his privileged connection with an epitaxior (his former student). Jusserand, in turn, could become significantly involved in terahertz and their interpretation, to ultimately be able to formulate analogies between acoustical and optical events. In effect this constituted a concrete window of opportunity in a domain that had long fascinated him and to which in the past he had only been able to contribute fitfully. By working with Perrin, Jusserand could investigate aperiodic materials.

The collaboration began with a gift from Jusserand to Perrin of a three to five semiconductor sample that he had in his drawer, suitable for Perrin’s exigencies. In a first article, published in 2004, the two scientists used their respective excitation devices, one a Raman and the other a picosecond laser pump-probe, to produce and study sound waves in a micro-cavity. Both Perrin and Jusserand had worked with micro-cavities in their preceding research on super-lattices, and on which Perrin had published articles belonging to this family of objects. Using the same sample, the two scientists could study two kinds of perturbations in a micro-cavity, one with light waves, the other with sound waves.

The perturbation induced by light can be referred to as an impulse. It may be likened to a swift hammer tap on a pendulum, which oscillates and then returns to its equilibrium state. The perturbation induced by sound can be described as a pendulum that is moved from one support to another. In this case, instead of immediately returning to its initial equilibrium, the system gradually finds a new equilibrium state. In the case of the impulsional light perturbation, the time is brief. In the case of the percussional perturbation, the time required to obtain equilibrium is relatively long, ranging from picoseconds to nanoseconds. For the two scientists, working together allowed them to explore the complex relations between the two forms of perturbations. The two-wave systems occurring together generate a family of highly original and complex phenomena.44 Nevertheless, with the first sample which they began to work on together, they could not obtain sufficiently elevated frequencies (terahertz were not attainable). In order to generate these, a new material would be required. This would take the form of a specially-tailored-to-need nanocavity, which was not then available to them. It thus had to be designed and synthesized. This task would fall to the epitaxior, Aristide Lemaître.

The pre-history of the nanocavity begins in 1992, when it was first predicted and described by simulation-based results;45 and the first physical nanocavities were synthesized two years later, in 1994.46 A nanocavity consists of a nanometric layer having specific properties located between two super-lattices. These objects proved extremely difficult to produce, and consequently their introduction into experimentation was slow (publication of only one article on this object in 1995, three in 1998, eight in 2000). It was only in 2005 that one can see the beginning of a stable and significant growth in the number of publications (91 articles). At this point, interest in the topic was not yet evident, and it is only from 2005 onwards that a momentum of concern, both in epitaxy works and in optics physics, really began to be perceptible. Here it is remarkable to note that the two most-cited articles dealing with nanocavities focus on epitaxy.47

The perceived necessity to obtain a nanocavity demonstrates the centrality of research-objects within nanoresearch. Research-objects determine the research that can be conducted. We will now see how the dialog between the experimenter physicists and the epitaxior who provides them with his tailored samples, structures the step-by-step work of defining and complexifying the experimental research question: the experimenters have questions that the epitaxior “translates” into the configurations and properties he is able to give to the materials; and it is these properties that the experimenters investigate. The evolution of Perrin and Jusserand’s subsequent exploration would depend on modifications of samples provided by Lemaître in his epitaxy laboratory.

Lemaître’s pivotal role consisted of constructing the nanocavities that were crucial to experiments. The conceptually and experimentally advanced and complex joint project of Perrin and Jusserand called for a highly sophisticated research-object consisting of two major modifications. The nanocavity has two Bragg mirrors,48 which confine optical and acoustical waves, and amplify them. This set-up allowed Perrin to use the physical object as a novel detection system. In most instances, the surface of the cavity that is excited to produce optical and acoustical effects also serves as a platform for the detection and study of vibration. The inconvenience of this approach is the differentiation of input and output. Perrin used the opposite side of the cavity as an alternative surface for detecting vibration, which yielded high-precision information.

In some of Jusserand and Perrin’s research, they insert a nanocavity inside a micro-cavity. This research-object posed acute epitaxial problems for Lemaître. It is no easy task to place a nanocavity inside a micro-cavity. The need to add a second Bragg mirror to a nanocavity meant a rethink of how to tailor this cavity. Nanocavities with Bragg mirrors have one smooth surface and another opposing rough surface. But in this case, the second mirror required a second smooth surface. The challenge consisted of generating the second smooth surface without abrading the first surface. In the discussion of what was required and reflections on how it could be achieved, Lemaître introduced several suggestions about what modifications to the object would be needed for the exploration of particular physical properties—such as the production of elevated terahertz. In some instances, the routine communication between Jusserand and Lemaître was complemented by joint meetings with Perrin, where Lemaître intervened in his capacity as a physicist and not only as epitaxior.

With the complex tailored nanocavity, Jusserand’s long-standing theoretical ambition to study the continuity between optical and acoustical waves in terms of phonons more exactingly became experimentally possible. Previously fragmented investigation of each of the two fields could now converge. For his part, Perrin’s objective to generate ever higher acoustical frequencies was realized thanks to a novel artifact. By moving from gigahertz to terahertz, he was able to explore a new acoustical vista and also to move toward assimilation of acoustical waves with heat waves. The goal of both scientists in their specific domains was predicated on the design and construction capability of epitaxy in the person of Lemaître. The joint advantage of the collaboration was expressed by Jusserand and Perrin in the following terms:

Their shared research results are reported in their numerous jointly signed articles—some 24 between 2004 and 2012—in top-rated journals such as Physical Review B, Applied Physics Letters, Physical Reviews Letters. They are also often cited in these and other high-ranked journals. Their work has met with considerable success, as illustrated by the birth of a research summer school entitled “Son et Lumière” (held every two years),50 where Jusserand’s guiding concept of an understanding about integrating optical and acoustical vibrations (in terms of phonons) is the central concept, and where Perrin’s idea of the continuity of this concept into heat may also be envisaged.

From its very beginning, Jusserand and Perrin’s project to work together can be seen as a synergistic dynamics: through their collaboration and the constant participation of Lemaître, Perrin and Jusserand have contributed to opening a field of research which is in itself at the juncture of two different problematics in physics: optical and acoustical wave propagation in a nanoscale research-object. This synergy renders even more relevant the question of control over the generation, description, and study of properties in nanoscale objects, and opens the way to broader horizons in other fields in physics research. Here epitaxy serves to stimulate research in two different research domains and functions as a pivot between them.

Perhaps most significantly, in NSR, the centrality of research-objects to projects brings to light the existence of a new relationship between the research question and the concrete possibility of experiment. In contrast with the past, when scientists often limited their questions to the possibilities of materials existing in nature, now in NSR practitioners are free to formulate questions in the knowledge that, through epitaxy and other materials synthesizing techniques, the desired research-objects carefully tailored to need can probably be generated. Such research by design constitutes a hallmark of NSR.

2.3 Metrological Experimentation and Simulation-Based Experimentation: Between Difficult Encounters and Synergy

The expansion of numerical simulation-driven experiments since the 1990s is particularly dramatic in nanoscale research, where the latter provides an inviting material and cognitive environment for convergence and intertwining of metrology experimentation and simulation. A newly emergent synergistic tandem between metrology and simulation experimentation is increasingly common, however this relationship does not prevent autonomous projects by the two groups.

These emerging orientations and complementarities are readily traced in the domain of nanoscale studies of surface science. Surface science constitutes a historical and strong theme in twentieth-century research. It began in the early part of the century, and its development equates with the discoveries of the chemists Paul Sabatier (Nobel Prize in chemistry in 1912), Fritz Haber (Nobel Prize in chemistry in 1918), Irving Langmuir (Nobel Prize in chemistry in 1932), and most recently, Gerhard Ertl (Nobel Prize in chemistry in 2007). Much surface physics deals with phenomena of molecular and atomic interfacing—solids and liquids, solids and gases, and gases and liquids. Interfaces are frequently studied with reference to charge, polarization, and energy.

The significance of a nanoscale perspective in surface science is that scientists, simulators, as well as metrologists, can study interfaces and surfaces at the atomic or molecular level (often in terms of single objects or deterministic, stabilized molecular ensembles), where they deal with the same objects and share a mutually intelligible language and set of images. Work processes and cognition of such research can be seen in the activities of a mixed metrology/simulation surface physics team, located at the Institut des Nanosciences de Paris (INSP), which mainly investigates hydroxylation and dissolution, specifically in thin films.51 This team focuses on oxide surfaces in nano-objects, which means thin oxide films, as opposed to bulk materials. They are particularly interested in the contact between oxide surfaces (frequently magnesium oxide) and water. The project consists of describing and explaining the surface configuration of atoms and their dynamics, and the question of dissolution mechanisms.

The simulators and metrologists studied here exhibit common features and also numerous particularities. As indicated earlier, the power of contemporary simulation resides in the development of algorithms and computational capacities that allow the treatment of an ever-increasing number of atoms. Using high-powered computers, simulators can effectively calculate the position and operation of a thousand atoms, or even thousands of atoms and their interactions. Some simulators declare that this development constitutes a better “fit with reality,”52 and better reflects the results of experimentation.

The restriction to a small number of atoms had long confined theoretical reflections to limited questions. The ability to include increasing quantities of atoms entails the possibility of dealing with a diversity of elements and their relations, and this complexity has led to the elaboration of reflection on the content and structure of physical systems at the nanoscale. In the confined spaces relevant to nanoscale research, what counts is not so much the number of atoms; it is instead to describe and analyze the complexities of the positions and relations of a spatially circ*mscribed ensemble, including forces. Algorithms are the heart of simulation. The work of many simulators includes writing new algorithms or adapting existing ones. The algorithms used in a particular simulation experiment are adapted to specific research materials and questions. They include certain hypotheses, focal points, and questions expressed through the introduction of numerical values and hierarchies of relations. As new materials are constantly being synthesized and additional research-objects are designed for study in nanoscale research, novel algorithms are correspondingly prepared. Algorithms express idealized substances and forces. Idealized substances and forces are viewed by simulators as “approximations.” The approximations are grounded on quantum theory, semi-empirical information, physical values presented in the scientific literature, and considerations of the specific experiment in progress. Within the limits of the logic of an algorithm, these approximations can be modified and managed. Idealizations and approximations are elastic to a certain degree.

Simulation permits the opening of two windows onto temporalities. Simulators are well positioned to explore dynamical properties of phenomena. They are free to introduce intervals of temporality into their numerical experiments that change the reciprocal values of entities. In the domain of thin oxide films, for example, simulation can introduce in a controlled way changes in form, scale, force relations, the position of molecules and atoms, and their state (polarity and energy) across time. One observes that the amount of attention given to questions of dynamics in simulation research is appreciably greater than in metrology-driven experimentation. Difficulties of control in metrology experimentation are far greater.

The second temporality deals with efficiency and speed, that are often equated with simulation. Computers can now carry out big and complicated calculations in relatively short periods. The preparation of algorithms and the introduction of selected quantitative data can also be done relatively quickly. Simulators frequently boast that their endeavors almost always outpace those of metrological experiments.

Simulators experience two types of limitation. Firstly, in spite of everything, computing power is not infinite. Secondly, the logic contained in algorithms defines and restricts what can be expressed and studied in a simulation finding. In thin-film oxide, emphasis is placed on periodicity—this may even be periodicity of defects. To a certain degree, the search for regularity is paramount. This contrasts with metrology experimentation, where practitioners keep an eye out for local strangeness—whatever does not fit into the anticipated pattern.

In experimental investigation of thin oxide films at the nanoscale, the instrument revolution offers new visual and observational possibilities. Metrology can now explore phenomena atom by atom and molecule by molecule, thanks to different kinds of scanning probe microscopy (STM and AFM, see Chapter 1). They can determine the presence or absence of a particular single atom, whether one atom is located on top of another atom, next to it, or comprises a bridge between two other atoms, etc. Based on relative position, metrology experimenters can deduce the forces at play. Beyond this, scanning probe microscopy gives scientists the sensation that they “see” individual elements in their sample. These elements exhibit an immediacy of presence. They are not perceived as mediated. Now, observation of atoms located on thin films means something very different from the collective diffraction points available in earlier categories of detection associated with diffraction and scattering.

Scientists see the surface and shape of nanoscopic objects, their materiality, and almost their palpability. This immediate and compelling quality of experimental observation differs from the idealized entities of simulation representations, where something of the object disappears. To quote one of the team senior scientists:

The observational perspective concentrates on the local. The local perspective generates decisive information about structures—in the case of thin oxide films, surface structures and relations between surface and environment. This stimulates reflection on the behavior of crystal surfaces and the dynamics of their dissolution.

The above claim of simulators that they are often free to work at an accelerated pace compared with metrology experimenters is not without truth. The director of the metrology-experimentation unit of the laboratory engaged in thin oxide film research that we investigated complained that it proved slow to be equipped—requiring several years. Experimenters had to assemble expensive, complicated, diversified instruments to perform their work. They then had to master the devices and to prepare them for their specific experiments. Finally, time was required to design the experiments. The time needed to conduct experiments is also considerable. There thus exists a great temporal lacuna between the relatively short time-scale of simulation and the comparatively long scale of metrology-based experimental work. This is in part due to several sorts of inertia. One consists of the often slow negotiation entailed in obtaining properly tailored research-objects. As indicated above, this includes the process of modifications in the samples. Changing the settings of the different parameters of a particular experimental run (pressure, temperature, magnetic and electric fields, wetness, etc.) is most of the time very delicate and time consuming.

While the cognitive objectives and work practices of simulators and metrology experimenters are often conspicuously different, this nevertheless leaves open the possibility of cooperation and synergy under particular conditions. As observed in our study, there are three permutations of relations between simulators and metrology experimenters: (1) simulation led, (2) metrology led, (3) simulators and metrology experimenters working in tandem.

2.3.1 Simulation-led enquiry

Particularly in new domains of research, such as are observed in nanoscale surface physics and notably in the case of the exploration of oxide, simulation frequently points in a direction that subsequently orients experimental studies. This occurs in a framework of prediction and it ultimately offers an explanation of metrological instrument experimental findings. At this scale, there exists a paucity of information, which makes the design and implementation of metrology experiments quite problematic. Simulation has allowed rapid exploration of the forces and entities characteristic of nanosurface physics oxide materials. In simulation, atoms can be shifted to the right or moved to the left and can be arranged in a variety of patterns. Alternative forces can be introduced, and their intensities increased or decreased. Simulation allows numeric experimentation that is unattainable by metrological experimentation. For example, the Schrödinger equation can be solved for very high energy levels; this solution is out of the reach of metrology-based experimenters.54 This offers the possibility of understanding a precise question (in this case the energy level of a particular surface of ultra-thin oxide) in a broader framework.

Through this play with hypothetical situations, simulators can determine what is physically coherent or incoherent. It establishes what is plausible. Based on plausibility, simulation predicts the outcomes of particular atomic and molecular configurations and forces. For example, in the recent past, it has not been possible to construct an experiment in which a gold atom could be deposited on an oxide surface. Although this experiment is now possible, it remains highly complicated. Conversely, the simulation ab initio method has proven highly effective in identifying the position of equilibrium of the gold atom on the surface. This anticipatory knowledge has made it easier for experimenters to design and conduct research projects. This episode illustrates a posture in which simulation opens the way for metrological experimental initiatives to occur at some undefined time in the future. Another routine aspect of simulation work is pure prediction. In the 1990s, the question of polarity was quite well understood for surfaces of bulk materials. Now, with the advent of nanostructured thin-film materials, a range of supplementary questions has arisen. Low-dimensional materials have consequences on surface phenomena that are different from those on the surfaces of bulk substances. Simulation techniques deal with these questions and have generated an ensemble of predictions, which call for experimental validation. Research on stability and electronic structure of polar surfaces at the nanoscale using simulation predicts that they are affected by the chemical material environment, which includes different expressions of titanium di-oxide and strontium mono-oxide. This prediction required the examination of parameters that are not easily accessible to experimenters and that are difficult to explore, such as Fermi bands.55

The centrality of prediction in simulation is illustrated by the following quotation:

The fact that prediction is central does not weaken our claim concerning the place of descriptivism in NSR. There is no strong reason for the one to deny the other. The co-existence of prediction and descriptivism are particularly palpable in their encounter. They are certainly not antithetic. It is not an either/or situation.

Another orientation of simulation-led research focuses on questions of morphology, spatial relations, and force. More precisely, simulation-based nanoscale research on oxides deals with five fundamental parameters: (1) the relative positions of atoms and molecules, (2) their shape, (3) environment, (4) energy, and (5) dynamics. The operation of these five components in a simulation research project is reflected in the following example.

Research is carried out on a model crystalline lattice and the effects of selectively cutting it, with particular attention to the position and the re-positioning of individual atoms. Figure 2.3 shows how the initial shape of a crystal determines the geometric transformations in the process of its growth.

This physicist closed the interview with the remark that this kind of calculation is specific to nanoscale objects, contrary to bulk objects, where every element is “identical.”

From the above, we see that shape, size, position, force, environment, etc. constitute the landscape of simulation. Numerical calculations of these parameters are bounded by the simulator’s background knowledge of the object. This physicist operates in a logic of constraints. One strength of simulation lies in the freedom to introduce values and configurations that stretch the envelope of conventional organizations and representations of objects. In so doing, new constraints may arise, as well as credible unanticipated systems. In this way, simulation switches back and forth between a terrain of logic and a kind of playfulness.

2.3.2 Metrology-led investigation

The development of instrumentation for experimental investigation at the nanoscale permits new questions or allows the framing of older questions in new terms. The possibility of observing new objects at this scale determines topics and the landscape and language of observation. In the physics of ultra-thin surfaces, metrology-equipped experimenters are now capable of identifying the position of individual atoms and the organization of clusters of atoms, and they can describe features of single molecules. When these scientists communicate their observations, they often speak in terms of the size, shape, relative spaces, and textures of materials. In this research work, however, characterization of entities is not the product of a calculation but is instead the result of observation and measurement. As will now be shown, experimenters’ vocabulary of description differs sharply from that of simulators.

When a surface of oxides observed at the nanoscale is portrayed by scanning probe microscopy using for example an AFM, it exhibits a totally chaotic landscape of mountains, plains, and valleys, marked by sharp edges, terraces, or steep steps. Such a description reminds one of the reports of Galileo when first gazing on the surface of the moon. This is the characteristic language used by metrology experimenters to describe and to understand surfaces at the nanoscale. Different aspects of forms and position are employed by these scientists to deduce the presence or absence of particular forces. In experimentation, forces are inferred from form and position. This can provide some indirect information on dynamics.

In surface physics, these morphologies and spaces are registered and captured as images. The images inform the objects—they are the informational foundation and representation of the object; and it is these images that are constitutive of discussion, intelligibility, and communication. The place of images will be discussed at length in Chapter 4. For the time being, we exhibit an image generated in the course of nanoscale research on oxide surfaces.

What scientists observe is a landscape of points, lines, curves, and spaces, which are often complicated and encumbered. Nanoscale surface scientists must next relate items one to another, and this requires selection. One can relate one point to many others, one complex configuration to another; the spacing between atoms in the image or the notion of directionality they suggest induces the researcher to select, to privilege certain links.

Depending on the status accorded to the link, it may be judged to constitute a physical relation. Such relations implicitly refer to some necessary interaction—chemical, electronic, magnetic, etc.

The following quotation demonstrates the centrality of form to observation as revealed through instrument-based images. The research carried out here deals with the dynamics of the dissolution of an oxide in an aqueous environment. In reading this passage, particular attention should be given to the language of description, which reveals key aspects of seeing and thinking of metrology informed experimentation work in this field.

In this example, mechanism may basically be understood as the chain of objects (forms) and events (transformations) that constitutes the dynamics in a process that goes from A to Z. Here, mechanism lies in the domain of description, and it may perhaps be likened to a film where physical laws play a certain role. This is a clear example of how morphology penetrates the observation of metrology experimenters working in this domain and how it affects language and logic. It is safe to say that the very substance of the questions asked by researchers flows from geometry-driven observation and reasoning.

Figure 2.4 depicts the progressive transformation of an MgO crystal in a process of dissolution. Photograph (a) shows well-defined square shapes exhibiting sharp edges and corners. Photograph (b) reveals changes in the form of the corners which may be likened to shallow stair steps. In photograph (c) the reader can observe a multitude of crystals with different geometries, corresponding to different states of dissolution: one can see almost perfect squares, octahedrons, lozenges resulting from the dissolution of octahedrons, etc.

Meaning is ground in the shapes of objects, and the shapes of objects are inextricably linked to description as understanding. Meaning is progressively developed from the resources of relations. Meaning here signifies the identification of the preferred organization and interactions of selected entities in the system under study. It is strongly related to the special coordinates of a system. This species of meaning is distinct from questions about how a system operates. For these experimenters, meaning refers to what and not how. “How” questions are associated with interpretation. Metrology-instrument experimenters sometimes engage in interpretation of the local system that they have observed. This is referred to as “experimental interpretation.” Beyond issues of experimental interpretation, the plausibility of interpretation frequently belongs, however, to the domain of simulation, as will be seen below, where metrology-instrument experimenters and simulators work in tandem.

2.3.3 Simulation/metrology tandems

Our earlier discussions focused on simulation-led and then on metrology-led research; we now turn to tandem projects. The research incident that we will term “the gray story” explores the contribution of simulation to processes of explanation in nanosurface physics investigations. In this episode, a metrology-based experimenter, who had measured the interface between a zinc/selenium semiconductor and iron, noted that the separation was not well differentiated. In his AFM images, he detected an ill-defined fuzzy region between the two substances that was neither white nor black, as should have been the case. At the nanoscale, atoms can be observed to interlace. Instead of having clear-cut black or white regions, the measurements done on the sample suggested that, at the interface between the two materials, there existed a gray zone consisting of a kind of intertwining. The experimenter contacted the simulator in search of an explanation. In view of the magnetic properties of iron, the simulator decided to attack the problem from the perspective of spin. The structures of iron and the semiconductor matched, and calculating their interface, he discovered remarkable properties concerning the injection of spin. However, the experimenter’s measurements did not confirm this result. The simulator next made new calculations and discovered the existence of an interface layer where iron mixed with the semiconductor. The existence of this interface appreciably degraded surface magneto-transport effects. The observed effect was hence not a simple matter of spin, as was initially suggested by simulation. In the “gray story,” after the questions raised by metrology and experimental rejection of the opening theoretical simulation explanation, the simulator ultimately provided a subtle explanation of the observed experimental findings, and also contributed to a finer understanding of magneto-transport dynamics.59

A last aspect of simulation/metrology work shifts attention back to the opening of this chapter, where it was pointed out that the synthesis of materials in the form of research-objects is crucial to nanoscale physics investigations. Section 2.2 accorded considerable importance, sometimes even center stage, to the technology of synthesis and its dynamic interaction with experiments. It has been demonstrated that linkage between experimenters and epitaxy often sophisticates and accelerates the synthesis of materials. The same can be said for interaction between simulation and development of epitaxy methods and performance. Epitaxy is certainly far from a low-theory field. Theories of the best conditions governing crystal growth and the utility and inconvenience of defects have considerably profited the science of nanoscale synthesis. Crystal growth entails insights into the energetics of structural composition and change, and this domain is precisely one kingdom of simulation in nanoscale surface physics. For example, the kinetic Monte Carlo method has been used to calculate growth mechanisms of a material like MgO with reference to surface roughness, size distribution, density of the islands, and filling ratios of the growing layers. It was calculated that the best growth occurs in an environment at above 700 K and a pressure of 0.1 Torr.60 Such simulation findings often prove important for the practice of epitaxy.

Conclusion

Our study of nanoscale physics research prompts three observations. First, in physics, research is conducted with reference to the size, shape, position, texture, and interaction of atoms and molecules. These features constitute the privileged language of observation and are central to intelligibility. Description is of foremost importance and argumentation and proof are often structured around it.

Second, synthesis of materials constitutes the central axis of nanoscale physics, onto which are grafted instruments, methods, questions, concepts, and skills, as well as the above-mentioned landscape of size, morphology, and position. Synthesis initially entails the fabrication of generic nanostructured materials and then it entails the labor of materials-by-design, where a research-object is built in response to the particular needs of a specific experimentation project. This draws attention to the capacity for control, which is a constant in nanophysics. Through precise tailoring of a substance, physical properties, previously unobserved, are produced and explored. Research-objects function as a bridge between synthesis and metrology experimentation, and in so doing they comprise a key combinatorial of NSR.

Third, in nanophysics, one can identify three principal cognitive, instrumental and technical groups: metrology-based experimenters, epitaxiors, and simulators. Each of these populations possesses specific skills. One characteristic of nanophysics may reside in the elevated amount of communication, even interlacing between the three bodies. We hypothesize that, due to the combinatorials of metrology/simulation collaborations and epitaxy/experimentation combinatorials (the hole underpinned by synthesis), synergy is possibly greater in nanoscale research than in other fields.