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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 paper, the first step of graphitization of ion-damaged pyrolytic graphite at annealing temperatures of −2300 C was shown to be possible.
Abstract: Post-implantation annealing of ion-damaged, highly oriented pyrolytic graphite has been studied by Raman spectroscopy, ion-channeling techniques, and transmission electron microscopy. Complementary information obtained by these methods provides confirmation for the first step of graphitization of ion-damaged graphite at annealing temperatures of \ensuremath{\sim}2300\ifmmode^\circ\else\textdegree\fi{}C. This is manifested by the formation of carbon planes with two-dimensional ordering but no correlation in the third ($c$-axis) dimension.

29 citations

Journal ArticleDOI
TL;DR: In this article, a set of phonon dispersion relations for EuSe in the GAMMA-L direction is constructed, which is consistent with a spin-disorder model.
Abstract: Detailed evidence is presented linking the Raman spectra in the magnetic semiconductors EuSe and EuS to their respective magnetic phase diagrams. In particular, spectra for EuSe are presented for the paramagnetic, ferromagnetic, antiferromagnetic (up-arrowup-arrowarrow-downarrow-down), and ferrimagnetic (up-arrowup-arrowarrow-down) spin arrangements and are related to a Brillouin-zone-folding scheme for each magnetic sublattice structure. Based on our spectra a set of phonon dispersion relations for EuSe in the GAMMA-L direction is constructed. We have also obtained for the first time right-angle Raman scattering spectra in EuSe. These results are compared with those obtained in the back-scattering geometry. Of significance is our observation that the broad spectral line extending from ..omega../sub TO/ to ..omega../sub LO/ in the paramagnetic phase persists for laser excitation energies below the fundamental absorption edge, thereby ruling out a hot luminescence mechanism for this feature. Instead, our results are consistent with a spin-disorder model. Resonant Raman enhancement results are given for scattering in ferromagnetically ordered EuS and EuSe, and are related to magnetic-field-modulated magnetoreflectivity spectra. Particular attention has been given to the magnetic-phase dependence of the EuSe modulated spectra in going from the ferrimagnetic to the ferromagnetic spin arrangements.

29 citations

Journal ArticleDOI
TL;DR: In this article, the concept of using self-assembled and force-engineered nanostructures to enhance the thermoelectric figure of merit relative to bulk homogeneous and composite materials is presented in general terms.
Abstract: The concept of using “self-assembled” and “force-engineered” nanostructures to enhance the thermoelectric figure of merit relative to bulk homogeneous and composite materials is presented in general terms. Specific application is made to the Si-Ge system for use in power generation at high temperature. The scientific advantages of the nanocomposite approach for the simultaneous increase in the power factor and decrease of the thermal conductivity are emphasized along with the practical advantages of having bulk samples for property measurements and a straightforward path to scale-up materials synthesis and integration of nanostructured materials into thermoelectric cooling and power generation devices.

29 citations

Journal ArticleDOI
TL;DR: Transport in photoactive graphene heterostructures is governed by the processes of thermionic emission, electron-lattice thermal imbalance, and cooling, which give rise to interesting photoresponse effects, in particular negative differential resistance (NDR) arising in the hot-carrier regime.
Abstract: Transport in photoactive graphene heterostructures, originating from the dynamics of photogenerated hot carriers, is governed by the processes of thermionic emission, electron–lattice thermal imbalance, and cooling. These processes give rise to interesting photoresponse effects, in particular negative differential resistance (NDR) arising in the hot-carrier regime. The NDR effect stems from a strong dependence of electron–lattice cooling on the carrier density, which results in the carrier temperature dropping precipitously upon increasing bias. The ON–OFF switching between the NDR regime and the conventional cold emission regime, as well as the gate-controlled closed-circuit current that is present at zero bias voltage, can serve as signatures of hot-carrier dominated transport.

29 citations

Journal ArticleDOI
TL;DR: In this article, the authors presented a grant for the development of a system for artificial neural networks in the context of the CNPq-CNPq grant 2007-7.
Abstract: Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) (Grant No. 550435/ 2007-7)

29 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