Graphene is a rapidly rising star on the horizon of materials science and condensed-matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic quality, and, despite its short history, has already revealed a cornucopia of new physics and potential applications, which are briefly discussed here. Whereas one can be certain of the realness of applications only when commercial products appear, graphene no longer requires any further proof of its importance in terms of fundamental physics. Owing to its unusual electronic spectrum, graphene has led to the emergence of a new paradigm of 'relativistic' condensed-matter physics, where quantum relativistic phenomena, some of which are unobservable in high-energy physics, can now be mimicked and tested in table-top experiments. More generally, graphene represents a conceptually new class of materials that are only one atom thick, and, on this basis, offers new inroads into low-dimensional physics that has never ceased to surprise and continues to provide a fertile ground for applications.

The rise of graphene

Graphene — a recently isolated one-atom-thick layered form of graphite — is a hot topic in the materials science and condensed matter physics communities, where it is proving to be a popular model system for investigation. An experiment involving individual graphene sheets suspended over a microscale scaffold has allowed structure determination using transmission electron microscopy and diffraction, perhaps paving the way towards an answer to the question of why graphene can exist at all. The 'two-dimensional' sheets, it seems, are not flat, but wavy. The undulations are less pronounced in a two-layer system, and disappear in multilayer samples. Learning more about this 'waviness' may reveal what makes these extremely thin carbon membranes so stable. Investigations of individual graphene sheets freely suspended on a microfabricated scaffold in vacuum or in air reveal that the membranes are not perfectly flat, but exhibit an intrinsic waviness, such that the surface normal varies by several degrees, and out-of-plane deformations reach 1 nm. The recent discovery of graphene has sparked much interest, thus far focused on the peculiar electronic structure of this material, in which charge carriers mimic massless relativistic particles1,2,3. However, the physical structure of graphene—a single layer of carbon atoms densely packed in a honeycomb crystal lattice—is also puzzling. On the one hand, graphene appears to be a strictly two-dimensional material, exhibiting such a high crystal quality that electrons can travel submicrometre distances without scattering. On the other hand, perfect two-dimensional crystals cannot exist in the free state, according to both theory and experiment4,5,6,7,8,9. This incompatibility can be avoided by arguing that all the graphene structures studied so far were an integral part of larger three-dimensional structures, either supported by a bulk substrate or embedded in a three-dimensional matrix1,2,3,9,10,11,12. Here we report on individual graphene sheets freely suspended on a microfabricated scaffold in vacuum or air. These membranes are only one atom thick, yet they still display long-range crystalline order. However, our studies by transmission electron microscopy also reveal that these suspended graphene sheets are not perfectly flat: they exhibit intrinsic microscopic roughening such that the surface normal varies by several degrees and out-of-plane deformations reach 1 nm. The atomically thin single-crystal membranes offer ample scope for fundamental research and new technologies, whereas the observed corrugations in the third dimension may provide subtle reasons for the stability of two-dimensional crystals13,14,15.

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The structure of suspended graphene sheets

The purpose of this article is to describe the basic physical processes involved in the nucleation and growth of thin films of materials on solid surfaces. In this introduction the three modes of crystal growth which are thought to occur on surfaces in the absence of interdiffusion are described, and the relationships between the thermodynamics of adsorption and the kinetics of crystal growth are explored in general terms. This is followed by a brief review of atomistic nucleation theory, explaining the relations of such theories to experimental observables. In the next three sections, recent experimental examples of these three growth modes are given, which are interpreted where possible in terms of nucleation and growth theory. The last section discusses observations on the shapes of growing crystallites and the relation of such observations to nucleation and surface diffusion processes.

https://iopscience.iop.org/article/10.1088/0034-4885/47/4/002/pdf

Nucleation and growth of thin films

During the past decade, enormous progress has been made in growing ultrathin organic films and multilayer structures with a wide range of exciting optoelectronic properties. This progress has been made possible by several important advances in our understanding of organic films and their modes of growth. Perhaps the single most important advance has been the use of ultrahigh vacuum (UHV) as a means to achieve, for the first time, monolayer control over the growth of organic thin films with extremely high chemical purity and structural precision.1-3 Such monolayer control has been possible for many years using well-known techniques such as Langmuir-Blodgett film deposition,4 and more recently, self-assembled monolayers from solution have also been achieved.5 However, ultrahighvacuum growth, sometimes referred to as organic molecular beam deposition (OMBD) or organic molecular beam epitaxy (OMBE), has the advantage of providing both layer thickness control and an atomically clean environment and substrate. When combined with the ability to perform in situ highresolution structural diagnostics of the films as they are being deposited, techniques such as OMBD have provided an entirely new prospect for understanding many of the fundamental structural and optoelectronic properties of ultrathin organic film systems. Since such systems are both of intrinsic as well as practical interest, substantial effort worldwide has been invested in attempting to grow and investigate the properties of such thin-film systems. This paper is a review of recent progress made in organic thin films grown in ultrahigh vacuum or using other vapor-phase deposition methods. We will describe the most important work which has been published in this field since the emergence of OMBD in the mid-1980s. Both the nature of thin-film growth and structural ordering will be discussed, as well as some of the more interesting consequences to the physical properties of such organic thin-film systems will be considered both from a theoretical as well as an experimental viewpoint. Indeed, it will 1793 Chem. Rev. 1997, 97, 1793−1896

Ultrathin Organic Films Grown by Organic Molecular Beam Deposition and Related Techniques.

Transparent conductors as solar energy materials: A panoramic review

The invention relates to a method for producing at least one cavity in a material (1) having a hexagonal or cubic crystallographic structure, especially a carbide and/or a material containing silicon, said method comprising the following steps: at least one initial etching point (2) is formed in the material (1) on at least one pre-determined site (3), and the cavity is etched from the initial point (2) previously formed by exposing the material to a reducing environment.

Method for producing at least one cavity in a material

http://www-old.mpi-halle.mpg.de/mpi/publi/pdf/3760_02.pdf

Margrit Hanbücken

Papers

Method for producing at least one cavity in a material

Scanning tunneling microscopy study of the stability of nanostructures on Si(1 1 1) at elevated temperature

Selective functionalization of substrates through assembled nanostructures: From physics to biology

Surface science lettersSurface cleaning of Si(100) and Ag/Si(100): Characterisation by SEM, AES and RHEED

Growth of Organised Nano-Objects on Prepatterned Surfaces