Mildred S. Dresselhaus

Bio: Mildred S. Dresselhaus is an academic researcher from Massachusetts Institute of Technology. The author has contributed to research in topics: Carbon nanotube & Raman spectroscopy. The author has an hindex of 136, co-authored 762 publications receiving 112525 citations. Previous affiliations of Mildred S. Dresselhaus include University of California, Los Angeles & Universidade Federal de Minas Gerais.

Far-infrared magnetoreflection studies of graphite intercalated with bromine

Abstract: An estimate of the hole generation rate in graphite-bromine residue compounds has been made from the interpretation of far-infrared magnetoreflection data. From the cutoff of the (1,2) Landau level transition due to the lowering of the Fermi energy upon bromine intercalation, we estimate that one hole is generated by 55 \ifmmode\pm\else\textpm\fi{} 10 ${\mathrm{Br}}_{2}$ intercalate molecules. This result is shown to be consistent with estimates based on transport measurements. Furthermore, the observed magnetoreflection resonances confirm that for these compounds ($\ensuremath{\lesssim}1$ mole% ${\mathrm{Br}}_{2}$) the electronic structure in the band overlap region is well described by the Slonczewski-Weiss-McClure band model for approximately the same values of the band parameters as for pure graphite.

Wall-to-wall stress induced in (6,5) semiconducting nanotubes by encapsulation in metallic outer tubes of different diameters: a resonance Raman study of individual C60-derived double-wall carbon nanotubes.

Abstract: We measure resonant Raman scattering from 11 individual C60-derived double-wall carbon nanotubes all having inner semiconducting (6,5) tubes and various outer metallic tubes. The Raman spectra show the radial breathing modes (RBM) of the inner and the outer tubes to be simultaneously in resonance with the same laser energy. We observe that an increase in the RBM frequency of the inner tubes is related to an increase in the RBM frequency of the outer tubes. The Raman spectra also contain a sharp G− feature that increases in frequency as the nominal diameter of the outer metallic tubes decreases. Finally, the one-phonon second-order D-band mode shows a two-way frequency splitting that decreases with decreasing nominal wall-to-wall distance. We suggest that the stress which increases with decreasing nominal wall-to-wall distance is responsible for the hardening that is observed in the frequencies of the RBM, D and G− modes of the inner (6,5) semiconducting tubes.

A revolution of nanoscale dimensions

Abstract: The continued drive to shrink the size and increase the functionality of electronic devices has seen the influence of nanotechnology strengthen as it offers materials with a layer thickness of one or a few atoms. Technological changes, awaited by computational scientists, are afoot. On the brink of the next revolution in electronic systems, nanomaterials and, in particular materials that are a few atoms thick are becoming increasingly apparent. Concurrently, computational scientists remain eager to see how Moore's Law will advance.

Bulk synthesis of narrow diameter and highly crystalline triple-walled carbon nanotubes by coalescing fullerene peapods.

Abstract: Carbon nanotubes exhibit unique physicochemical properties and electronic structure according to their chirality and the number of layers. [ 1–3 ] Triple-walled carbon nanotubes (TWNTs) consisting of three concentric graphene nanotubes provide many opportunities for systematic studies of carbon nanotube systems by comparing their behaviors with that of single-, double-, and multiwalled carbon nanotubes (SWNTs, DWNTs, and MWNTs, respectively). Their versatile chirality confi gurations, due to their three respective components, each of which can be either semiconducting or metallic, will allow TWNTs to have intrinsically unique physics that is not observed in SWNTs or DWNTs. Very recently, several attempts at synthesizing TWNTs have been reported by chemical vapor deposition (CVD), [ 4–7 ] thermal treatment of DWNTs encapsulating fullerenes, [ 8 ] and thermal decomposition of DWNTs encapsulating ferrocene [ 9 ] . Among these methods, the thermal treatment of DWNTs encapsulating fullerenes is expected to result in high-quality TWNTs, similar to the growth of DWNTs from the coalescence of fullerenes. [ 9–13 ] However, both the quality and morphology of TWNTs strongly depend on their growth conditions, such as the precursor that is used and the fi lling ratio of the fullerenes, the annealing temperature, and

Double-wall carbon nanotubes doped with different Br2 doping levels: a resonance Raman study.

Abstract: This report focuses on the effects of different Br2 doping levels on the radial breathing modes of “double-wall carbon nanotube (DWNT) buckypaper”. The resonance Raman profile of the Br2 bands are shown for different DWNT configurations with different Br2 doping levels. Near the maximum intensity of the resonance Raman profile, mainly the Br2 molecules adsorbed on the DWNT surface contribute strongly to the observed ωBr−Br Raman signal.

Electric Field Effect in Atomically Thin Carbon Films

Abstract: We describe monocrystalline graphitic films, which are a few atoms thick but are nonetheless stable under ambient conditions, metallic, and of remarkably high quality. The films are found to be a two-dimensional semimetal with a tiny overlap between valence and conductance bands, and they exhibit a strong ambipolar electric field effect such that electrons and holes in concentrations up to 10 13 per square centimeter and with room-temperature mobilities of ∼10,000 square centimeters per volt-second can be induced by applying gate voltage.

Helical microtubules of graphitic carbon

Abstract: THE synthesis of molecular carbon structures in the form of C60 and other fullerenes1 has stimulated intense interest in the structures accessible to graphitic carbon sheets. Here I report the preparation of a new type of finite carbon structure consisting of needle-like tubes. Produced using an arc-discharge evaporation method similar to that used for fullerene synthesis, the needles grow at the negative end of the electrode used for the arc discharge. Electron microscopy reveals that each needle comprises coaxial tubes of graphitic sheets, ranging in number from 2 up to about 50. On each tube the carbon-atom hexagons are arranged in a helical fashion about the needle axis. The helical pitch varies from needle to needle and from tube to tube within a single needle. It appears that this helical structure may aid the growth process. The formation of these needles, ranging from a few to a few tens of nanometres in diameter, suggests that engineering of carbon structures should be possible on scales considerably greater than those relevant to the fullerenes. On 7 November 1991, Sumio Iijima announced in Nature the preparation of nanometre-size, needle-like tubes of carbon — now familiar as 'nanotubes'. Used in microelectronic circuitry and microscopy, and as a tool to test quantum mechanics and model biological systems, nanotubes seem to have unlimited potential.

The rise of graphene

Abstract: 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.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

The electronic properties of graphene

Abstract: This article reviews the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations. The Dirac electrons can be controlled by application of external electric and magnetic fields, or by altering sample geometry and/or topology. The Dirac electrons behave in unusual ways in tunneling, confinement, and the integer quantum Hall effect. The electronic properties of graphene stacks are discussed and vary with stacking order and number of layers. Edge (surface) states in graphene depend on the edge termination (zigzag or armchair) and affect the physical properties of nanoribbons. Different types of disorder modify the Dirac equation leading to unusual spectroscopic and transport properties. The effects of electron-electron and electron-phonon interactions in single layer and multilayer graphene are also presented.