vol III chap 11 sect 3
Volume III: Waves
Previous: 11.2 Production of new materials and study of individual quantum systems.
11.3. Phases in a learning and research process.
In this section we describe Geim´s Nobel Lecture Random Walk to Graphene: MLA style: Andre Geim – Nobel Lecture. NobelPrize.org. Nobel Prize Outreach AB 2023. Sun. 28 May 2023.https://www.nobelprize.org/prizes/physics/2010/geim/lecture/
We analyze this Lecture as a learning and research process that involves two structural phases:
• The learning phase is for inquiring and exploring and comprehend the steps of motivation and problematization in connection with the acquisition of existing knowledge and the development of skills.
• The research phase is for evaluating and communicating and consists in the description of testing, discovery and publishing concerning the steps of experimentation and problematization for the development and application of new knowledge and the confrontation with external ideas, methods, and results.
In what follows we present a set of Tables describing the content of Geim´s Lecture. The title of each Table refers to the corresponding subtitle included in the original document. The first column in the Table describes reported activities by directly quoting or summarizing what is written in each section of the Lecture. The next five columns of the Table refer to those steps that we consider mainly correspond to motivation (Motv), problematization (Prob), experimentation (Expm), testing (Tstn), or publication (Publ). We indicate with an X the steps that we estimate have been predominantly involved in each activity. For simplicity, we omit many names and simplify the descriptions of such activities. These tables represent the trajectory of a learning and research process that started with a PhD dissertation and lead to a Nobel Prize.
Geim starts his Nobel Lecture with this remark: “I hope that the reader will excuse me if on this occasion I recommend my own writings [1–3]. Instead of repeating myself here, I have chosen to describe my twisty scientific road that eventually led to the Nobel Prize. Most parts of this story are not described anywhere else, and its timeline covers the period from my PhD in 1987 to the moment when our 2004 paper, recognized by the Nobel Committee, was accepted for publication.”
- A. K. Geim, K. S. Novoselov. Nature Mater. 6, 183 (2007).
- A. K. Geim, P. Kim. Sci. Am. 298, 90 (2008).
- A. K. Geim. Science 324, 1530 (2009).
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Table 11.1. Zombie management.
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ACTIVITY
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Motv
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Prob
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Expm
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Tstn
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Publ
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PhD dissertation in 1987: *Investigation of mechanisms of transport relaxation in metals by a helicon resonance method*.
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X
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X
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Work at the Institute of Microelectronics Technology on a personal project for fabricating a sandwich consisting of a thin metal film and a [superconductor](https://en.wikipedia.org/wiki/Superconductivity) separated by a thin insulator.
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Experimental report on the introduction of a new experimental system concerning electron transport in a microscopically inhomogeneous field (1989).
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Table 11.2. One man’s junk, another man’s gold.
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ACTIVITY
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Motv
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Prob
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Expm
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Tstn
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Publ
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Six month visiting fellowship to study devices readily available at a laboratory in Nottingham University in the United Kingdom; two publications in Physical Review Letters (1991, 1992).
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X
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Work as postdoc in European universities during four years for studying mesoscopic systems and phenomena such as two-dimensional electron gases, quantum point contacts, resonant tunnelling, and [quantum Hall effect](https://en.wikipedia.org/wiki/Quantum_Hall_effect).
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Familiarization with heterostructures grown by molecular beam epitaxy and improvement of personal expertise in microfabrication and electron-beam lithography technologies.
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Table 11.3. Dutch comfort.
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ACTIVITY
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Motv
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Prob
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Expm
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Tstn
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Publ
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Looking for a permanent academic position (1994).
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Associate professors at Nijmegen’s High Field Magnet Laboratory in the Netherlands.
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Studies of mesoscopic superconductivity and development of an original technique of ballistic Hall micromagnetometry (1997).
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Publication of papers on paramagnetic Meissner effect, vortices carrying fractional flux, vortex configurations in confined geometries and so on.
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Table 11.4. A spell of levity.
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ACTIVITY
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Motv
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Prob
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Expm
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Tstn
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Publ
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Work on [magnetic water](https://en.wikipedia.org/wiki/Magnetic_water_treatment) (liquid magnetized under an applied magnetic field); looking for the physics behind these phenomena (diamagnetism ).
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X
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Production of balls of levitating water; experiments with a levitating frog and other objects floating inside a magnet; publication in Physics Today (1998).
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X
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Table 11.5. Friday night experiments.
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ACTIVITY
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Motv
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Prob
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Expm
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Tstn
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Publ
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Experimental exploratory detours: it requires lateral thinking and digging through irrelevant literature without any clear idea in sight to get a feeling of what could be interesting to explore.
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Proof-of-concept experiments to make a material that mimicked the climbing ability of [geckos](https://en.wikipedia.org/wiki/Gecko) (their hairs are attached to the opposite surface of a glass due to a van der Waals attractive force).
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Table 11.6. Better to be wrong than boring.
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ACTIVITY
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Motv
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Expm
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Tstn
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A list of Friday night experiments performed in a period of nearly fifteen years contains failures like the interpretation of giant [diamagnetism](https://en.wikipedia.org/wiki/Diamagnetism) in alloys as a sign of high-T superconductivity or the detection of “heartbeats” of individual living cells.
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However, we succeed in topics such as [levitation](https://en.wikipedia.org/wiki/Levitation_(physics)), gecko tape and graphene. “When one dares to try, rewards are not guaranteed, but at least it is an adventure.”
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Table 11.7. The Mancunian way.
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ACTIVITY
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Motv
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Prob
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Expm
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Tstn
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Publ
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Full professorship at the University of Manchester for him and lectureship for his wife Irina Grigorieva. A first grant of £500K is for acquiring essential equipment. Publication of papers in Nature, Nature Materials, and Physical Review Letters.
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X
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Creation of the Manchester Centre for Mesoscience and Nanotechnology as a fully functional laboratory and a microfabrication facility dedicated to the production of new structures and devices. The funding normally goes to researchers who work both efficiently and hard.
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X
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X
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Table 11.8. Three little clouds.
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ACTIVITY
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Motv
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Prob
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Expm
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Tstn
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Publ
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Arrival of the first Manchester PhD student and suggestion of a new lateral experiment as research project: to make films of graphite ‘as thin as possible’ and, if successful, to study their ‘mesoscopic’ properties (2002).
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Appearance of three badly shaped thought clouds: concept of ‘metallic electronics”, [carbon nanotubes](https://en.wikipedia.org/wiki/Carbon_nanotube), and intercalated graphite compounds. The three thought clouds merged into the PhD project.
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Table 11.9. Legend of a Scotch tape.
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ACTIVITY
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Motv
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Prob
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Expm
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Tstn
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Publ
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The student was asked to make thin graphite films in a tablet of pyrolytic graphite, which was several mm thick and an inch in diameter. The student was advised to employ a polishing machine and to use a finer polishing liquid. He will work with a high-density graphite instead of highly oriented pyrolytic graphite.
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Another collaborator started working on a piece of cellotape with graphite flakes attached to it. He has been using a fresh surface of graphite by removing a top layer with sticky tape. Geim observed in a microscope at the remnants of graphite and found pieces much thinner than those obtained with the polishing machine.
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Geim and a new collaborator decided to check out the electrical properties of the graphite flakes found on the cellotape and to transfer them onto [glass](https://en.wikipedia.org/wiki/Glass) slides by using tweezers.
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Geim suggested the use of an oxidized Si wafers as substrates. Placing thin graphite fragments onto those wafers allowed to observe interference colours indicating that some of the fragments were optically transparent. Some of these fragments were just a few nm thick: this was a first real breakthrough.
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Geim used to work in the lab preparing samples, doing measurements, and analyzing results; nevertheless, after 2006 he needed to focus on writing papers and analyzing data.
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Table 11.10. Eureka moment.
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ACTIVITY
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Motv
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Prob
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Expm
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Tstn
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Publ
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The research goal always was to find some exciting physics rather than just observing ultrathin films in a microscope.
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The Scotch tape technique was used for the isolation and identification of ultra-thin graphite films and graphene. Silver paint was employed to make electrical contacts to graphite platelets transferred from the Scotch tape. The prepared material resulted in higher conductivity and reasonably low resistance.
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Transfer of graphite crystal from the tape was made by using tweezers to make four closely spaced contacts required for the application of voltage; the fingers were used to apply silver paint with a toothpick. The crystal was nearly 20 nm thick and its lateral size comparable to the diameter of a human hair.
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Detection of very small EFE (electric field effect) when a voltage was applied to the glass slides. After this discovery the project was oriented to improve procedures for cleaving, to find thinner and thinner crystals, and to make better and better devices. Crystal sizes went up from a few microns to nearly a millimeter.
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Learning how to identify monolayers by using optical and [atomic force microscopy.](https://en.wikipedia.org/wiki/Atomic_force_microscopy)
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Concerning microfabrication, the electron-beam [lithography](https://en.wikipedia.org/wiki/Lithography) was used to define proper Hall bar devices and started making contacts by metal evaporation rather than silver painting.
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The move from multilayers to monolayers and from hand-made to lithography devices was conceptually simple but never straightforward.
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Careful and complete electrical measurements were made to study more than 50 ultra-thin devices by working fourteen hours per day and no breaks for the weekends. We disregarded any curve, unless it was reproducible for many devices and, to avoid any premature conclusions.
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By the end of 2003, we got a reliable experimental picture ready for publication. We submitted the paper in a high-profile journal. It was rejected twice and one of the referees considered that our report did “not constitute a sufficient scientific advance.” The paper was published in *Science* **306**, 666 (2004).
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Table 11.11. Defiant existence.
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ACTIVITY
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Motv
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Prob
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Expm
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Tstn
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Publ
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According to our observations, the isolated atomic planes remained continuous and conductive under ambient conditions. There are four reasons to be surprised although they can be explained.
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(1) Collective experience in studies of ultra-thin films have proved that continuous monolayers are practically impossible to make. A metal film a few nm in thickness coagulates into tiny islands when it evaporates.
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(2) Theory unequivocally tells us that an isolated graphene sheet should be thermodynamically unstable. Larger graphene sheets are unstable with respect to scrolling.
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(3) 2D crystals cannot be grown in isolation, without an [epitaxial substrate](https://en.wikipedia.org/wiki/Epitaxial_wafer) that provides an additional atomic bonding. The density of thermal fluctuations for a 2D crystal in the 3D space diverges with temperature.
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(4) Graphene remains stable under ambient conditions. Surfaces of materials can react with air and moisture, and monolayer graphene has not one but two surfaces, making it more reactive.
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Table 11.12. Requiem for brilliant ideas.
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ACTIVITY
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Motv
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Prob
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Expm
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Tstn
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Publ
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Every idea is always based on previous knowledge and the odds are that someone somewhere had already thought of something similar before. Nevertheless, new technologies offer a reasonable chance that old, failed ideas may work unpredictably well the next time round.
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The 2004 paper demonstrated the experimental progress achieved to overcome the challenges of obtaining isolated [2D crystals](https://en.wikipedia.org/wiki/Single-layer_materials), their thermodynamic instability, the observation of nanoscrolls, and papers on epitaxial growth.
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Table 11.13. Graphene incarnations.
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ACTIVITY
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Motv
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Expm
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Tstn
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Publ
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The beginning of graphene history is the observation by the British chemist Benjamin Brodie (1783-1862) who in 1859 obtained what he called ‘[carbonic acid](https://en.wikipedia.org/wiki/Carbonic_acid)’ by exposing graphite to strong acids. What he observed was a suspension of tiny crystals of graphene oxide.
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During the last century the laminated structure of graphite oxide was described and a proof that the ‘carbonic acid’ consisted of floating atomic planes was presented.
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Creased flakes down to a few nm in thickness were observed by using [transmission electron microscopy](https://en.wikipedia.org/wiki/Transmission_electron_microscopy) (TEM).
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By using TEM Geim and a collaborator failed to distinguish between monolayers and somewhat thicker flakes by using only their TEM contrast.
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In 1986 Hanns-Peter Boehm (1928-2022) and his colleagues introduced the term graphene: a combination of the word ‘graphite’ and the suffix that refers to polycyclic aromatic hydrocarbons.
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Ultra-thin graphitic films and, sometimes, even monolayers were grown on metal substrates, insulating carbides and graphite. Epitaxial growth on insulating substrates was first demonstrated in 1975.
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In 1984 and 1988 it was suggested in that graphene could provide a nice condensed-matter analogue of (2+1) dimensional quantum electrodynamics.
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It was reported in 1990 that ‘peeling optically thin layers with transparent tape’ (Scotch tape), were used to study carrier dynamics in graphite.
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Table 11.14. Πλανητη Graphene.
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ACTIVITY
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Motv
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Expm
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Tstn
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Publ
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Earlier experiments were observational; they observed ultra-thin graphitic films, and occasionally even [monolayers](https://en.wikipedia.org/wiki/Monolayer) without reporting any of graphene’s distinguishing properties; there were few electrical and optical measurements.
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The method of graphene isolation and identification described in the 2004 Science paper is straightforward and accessible. That paper reported the application of an ambipolar electric field effect in which resistivity changed by a factor of the order of 100. There the properties of graphene were altered by simply varying the gate voltage.
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Graphene was completely unprotected from the environment, as it was placed on a microscopically rough substrate and covered from both sides with adsorbates and a polymer residue. Still, electrons could travel submicron distances without scattering, flouting all the elements outside.
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In [semiconductor](https://en.wikipedia.org/wiki/Semiconductor) physics, electronic quality is described in terms of charge carrier mobility µ = 10,000 $cm^2/Vs$. In 2010 Geim´s group reported a value 10 and 100 times higher at room and low temperature, respectively.
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Graphene history has something in common with that of solar planets. Ancient Greeks observed them and called them wandering stars. After the physics behind this wandering was discovered, people started perceiving planets quite differently. Similarly, during the last six years people discovered what graphene really is, which completely changed the earlier perception.
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Table 11.15. Magic of flat Carbon.
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ACTIVITY
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Motv
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Expm
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Tstn
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Publ
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In 2005 we demonstrated that charge carriers in graphene are massless [fermions](https://en.wikipedia.org/wiki/Fermion) described by a Dirac-like equation rather than by the standard Schrödinger equation.
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We also found in 2010 that graphene remained metallic in the limit of no charge carriers, even when just a few electrons remained present in a micron-sized device.
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In 2006 we suggested that the phenomenon of [Klein tunnelling](n.wikipedia.org/wiki/Klein_paradox), which was known in relativistic quantum physics for many decades but assumed non-observable, could be probed using graphene devices.
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We have shown in 2007 that bilayer graphene was a tuneable-gap semiconductor and demonstrated in 2009 that graphene could be carved into devices on a true nm scale.
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In 2009 and 2010 we made the first step into graphene chemistry by experimentally introducing its derivatives, graphane and stoichiometric fluorographene.
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Table 11.16. Ode to one.
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Tstn
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Despite the fact that graphite as graphene has many atomic layers stacked on top of each other, the following differences exist:
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(1) Graphene exhibits record stiffness and mechanical strength.
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(2) Graphene chemistry is different depending on whether one or both surfaces of a monolayer are exposed,
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(3) An electric field is screened in graphite at distances of about the interlayer separation, and the electric screening becomes important even for a bilayer; however, for multilayer graphene the electric field can dope no more than a couple of near-surface atomic planes, leaving the bulk unaffected.
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(4) [Charge carriers](https://en.wikipedia.org/wiki/Charge_carrier) in a monolayer are massless Dirac fermions whereas they are massive in a graphene bilayer
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Table 11.17. To colleagues and friends.
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Tstn
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Recognitions and acknowledgements to collaborators.
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REFERENCES
Physics and Chemistry Nobel Prizes
MLA style: Speed read: Crystal Patterns Made Plane and Simple. NobelPrize.org. Nobel Prize Outreach AB 2023. Wed. 24 May 2023. https://www.nobelprize.org/prizes/physics/1915/speedread/
MLA style: Speed read: Crystal Patterns Made Plane and Simple. NobelPrize.org. Nobel Prize Outreach AB 2024. Mon. 5 Feb 2024. https://www.nobelprize.org/prizes/physics/1915/speedread/
MLA style: Perspectives: Life through a Lens. NobelPrize.org. Nobel Prize Outreach AB 2023. Thu. 25 May 2023. https://www.nobelprize.org/prizes/physics/1986/perspectives/
MLA style: Press release. NobelPrize.org. Nobel Prize Outreach AB 2023. Thu. 25 May 2023. https://www.nobelprize.org/prizes/physics/1986/press-release/
MLA style: Popular information. NobelPrize.org. Nobel Prize Outreach AB 2023. Wed. 24 May 2023. https://www.nobelprize.org/prizes/physics/2010/popular-information/
MLA style: Press release. NobelPrize.org. Nobel Prize Outreach AB 2024. Tue. 6 Feb 2024. https://www.nobelprize.org/prizes/chemistry/1996/press-release/
MLA style: Advanced information. NobelPrize.org. Nobel Prize Outreach AB 2023. Sat. 10 Jun 2023. https://www.nobelprize.org/prizes/physics/2012/advanced-information/
Next: 12.1. Boson condensation.