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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.


Papers
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Journal ArticleDOI
TL;DR: In this article, the effect of texturing in polycrystalline bismuth thin films was investigated using magneto-resistance measurements, and it was shown that the anisotropic conduction is a result of the large electron effective mass anisotropy.
Abstract: We use magneto-resistance measurements to investigate the effect of texturing in polycrystalline bismuth thin films. Electrical current in bismuth films with texturing such that all grains are oriented with the trigonal axis normal to the film plane is found to flow in an isotropic manner. By contrast, bismuth films with no texture such that not all grains have the same crystallographic orientation exhibit anisotropic current flow, giving rise to preferential current flow pathways in each grain depending on its orientation. Extraction of the mobility and the phase coherence length in both types of films indicates that carrier scattering is not responsible for the observed anisotropic conduction. Evidence from control experiments on antimony thin films suggests that the anisotropy is a result of bismuth's large electron effective mass anisotropy.

6 citations

Journal ArticleDOI
TL;DR: In this article, single crystal bismuth nanowires with diameters ranging from 10 to 200nm and lengths of approx. 50 microns have been synthesized by pressure injecting molten bistuth into anodic alumina templates, and a scheme for measuring the resistance of a single Bi nanowire using a 4-point measurement technique.
Abstract: : We have synthesized single crystal bismuth nanowires by pressure injecting molten Bi into anodic alumina templates. By varying the template fabrication conditions nanowires with diameters ranging from 10 to 200nm and lengths of approx. 50 microns can be produced. We present a scheme for measuring the resistance of a single Bi nanowire using a 4-point measurement technique. The nanowires are found to have a 7nm thick oxide layer which causes very high contact resistance when electrodes are patterned on top of the nanowires. The oxide is found to be resilient to acid etching, but can be successfully reduced in high temperature hydrogen and ammonia environments. The reformation time of the oxide in air is found to be less than 1 minute. Focused ion beam milling is attempted as an alternate solution to oxide removal.

6 citations

Journal ArticleDOI
TL;DR: In this paper, the chirality distribution of a synthesized single-walled carbon nanotube (SWNT) material is characterized using Resonant Raman spectroscopy with a tunable excitation source.
Abstract: We have developed a methodology to use resonant Raman spectroscopy with a tunable excitation source to characterize the chirality distribution of a synthesized single-walled carbon nanotube (SWNT) material. Isolated SWNTs are either dispersed or directly grown on substrates with markers. The samples are then placed on an automatic scanning stage of a confocal Raman microscope. Resonant Raman signals from SWNTs are collected while the laser spot scans across the substrate and a two-dimensional mapping is obtained at each laser excitation energy. From the resonant Raman signal the chiralities of the SWNTs can be assigned and a chirality distribution of the material can therefore be obtained by examining hundreds to thousands SWNTs on the substrate.

6 citations

Journal ArticleDOI
TL;DR: In this article, the authors used the interface energies calculated by first-principles calculations to parameterize the pair interaction energies used in the Kinetic Monte Carlo algorithm to predict the solubility limit of solute atoms in a binary alloy.
Abstract: We developed a way to predict the solubility limit of solute atoms in a binary alloy using a Kinetic Monte Carlo algorithm. The idea is to use the interface energies calculated by first-principles calculations to parameterize the pair interaction energies used in the Kinetic Monte Carlo algorithm. In order to validate this method, it was tested on a very well known case: the Ni-Al alloy. We found that the calculations are in very good agreement with the previously calculated phase diagrams.

6 citations

Book ChapterDOI
01 Jan 1992
TL;DR: In this article, the structure and magnetic properties of magnetic acceptor and donor graphite intercalation compounds (GICs) are reviewed and compared with recent evidence for 2D magnetism in acceptor GICs.
Abstract: Magnetic graphite intercalation compounds are layered magnetic materials in which the ratio of the intraplanar to interplanar exchange coupling can be varied by several orders of magnitude through intercalation and staging. In this chapter, the structure and magnetic properties of magnetic acceptor and donor graphite intercalation compounds (GICs) are reviewed. The relation between the GIC and the pristine intercalate makes it possible to measure the effect of staging in the GIC, including the crossover to lower dimensionality. The theory of two-dimensional (2D) magnetism is reviewed and compared with recent evidence for 2D magnetism in acceptor graphite intercalation compounds. The transition-metal dichloride acceptor compounds show larger magnetic anisotropies than the donor GICs and provide instructive examples of quasi-2D magnetic systems. The prototype 2D-XY system is the CoCl2 GIC, for which a large body of experimental data is presented to infer the 2D behavior. Experimental results for the commensurate stage-1 donor compound C6Eu are presented as an example of an anisotropic RKKY magnetic interaction. In addition, progress in the study of many magnetic acceptor GICs is reviewed.

6 citations


Cited by
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Journal ArticleDOI
22 Oct 2004-Science
TL;DR: Monocrystalline graphitic 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.
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.

55,532 citations

Journal ArticleDOI
Sumio Iijima1
01 Nov 1991-Nature
TL;DR: Iijima et al. as mentioned in this paper reported the preparation of a new type of finite carbon structure consisting of needle-like tubes, which were produced using an arc-discharge evaporation method similar to that used for fullerene synthesis.
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.

39,086 citations

Journal ArticleDOI
TL;DR: 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 can now be mimicked and tested in table-top experiments.
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.

35,293 citations

01 May 1993
TL;DR: 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.
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.

29,323 citations

Journal ArticleDOI
TL;DR: In this paper, the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations, are discussed.
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.

20,824 citations