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A. L. Efros

Bio: A. L. Efros is an academic researcher from University of Utah. The author has contributed to research in topics: Density of states & Variable-range hopping. The author has an hindex of 15, co-authored 35 publications receiving 6805 citations. Previous affiliations of A. L. Efros include Russian Academy of Sciences & Max Planck Society.

Papers
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01 Jan 1984
TL;DR: In the last fifteen years, there has been a noticeable shift towards impure semiconductors -a shift which came about because it is precisely the impurities that are essential to a number of major semiconductor devices.
Abstract: First-generation semiconductors could not be properly termed "doped- they were simply very impure. Uncontrolled impurities hindered the discovery of physical laws, baffling researchers and evoking pessimism and derision in advocates of the burgeoning "pure" physical disciplines. The eventual banish ment of the "dirt" heralded a new era in semiconductor physics, an era that had "purity" as its motto. It was this era that yielded the successes of the 1950s and brought about a new technology of "semiconductor electronics." Experiments with pure crystals provided a powerful stimulus to the develop ment of semiconductor theory. New methods and theories were developed and tested: the effective-mass method for complex bands, the theory of impurity states, and the theory of kinetic phenomena. These developments constitute what is now known as semiconductor phys ics. In the last fifteen years, however, there has been a noticeable shift towards impure semiconductors - a shift which came about because it is precisely the impurities that are essential to a number of major semiconductor devices. Technology needs impure semiconductors, which unlike the first-generation items, are termed "doped" rather than "impure" to indicate that the impurity levels can now be controlled to a certain extent."

1,904 citations

Journal ArticleDOI
TL;DR: In this paper, the Coulomb interaction between localized electrons is shown to create a soft gap in the density of states near the Fermi level, and the form of the density within the gap is discussed.
Abstract: The Coulomb interaction between localized electrons is shown to create a 'soft' gap in the density of states near the Fermi level. The new temperature dependence of the hopping DC conductivity is the most important manifestation of the gap. The form of the density of states within the gap is discussed.

1,763 citations

Book
05 Oct 2014
TL;DR: In the last fifteen years, there has been a noticeable shift towards impure semiconductors -a shift which came about because it is precisely the impurities that are essential to a number of major semiconductor devices as discussed by the authors.
Abstract: First-generation semiconductors could not be properly termed "doped- they were simply very impure. Uncontrolled impurities hindered the discovery of physical laws, baffling researchers and evoking pessimism and derision in advocates of the burgeoning "pure" physical disciplines. The eventual banish ment of the "dirt" heralded a new era in semiconductor physics, an era that had "purity" as its motto. It was this era that yielded the successes of the 1950s and brought about a new technology of "semiconductor electronics." Experiments with pure crystals provided a powerful stimulus to the develop ment of semiconductor theory. New methods and theories were developed and tested: the effective-mass method for complex bands, the theory of impurity states, and the theory of kinetic phenomena. These developments constitute what is now known as semiconductor phys ics. In the last fifteen years, however, there has been a noticeable shift towards impure semiconductors - a shift which came about because it is precisely the impurities that are essential to a number of major semiconductor devices. Technology needs impure semiconductors, which unlike the first-generation items, are termed "doped" rather than "impure" to indicate that the impurity levels can now be controlled to a certain extent."

1,243 citations

Book
01 Jan 1985
TL;DR: In this paper, the effect of Coulomb interactions on electronic states and tansport in disordered insulators is discussed. But the Coulomb interaction is not considered in this paper.
Abstract: Introduction (Sir Nevill Mott). 1. Electron-electron interaction in disordered conductors (B.L. Altshuler and A.G. Aronov). 2. Interaction effects in the weakly localized regime of two- and three-dimensional disordered systems (H. Fukuyama). 3. A review of the metal-insulator transition in doped semiconductors (R.F. Milligan, T.F. Rosenbaum, R.N. Bhatt and G.A. Thomas). 4. The effect of Coulomb interactions on electronic states and tansport in disordered insulators (M. Pollak and M. Ortu#o). 5. Coulomb interaction in disordered systems with localized electronic states (A.L. Efros and B.I. Shklovskii). 6. H - -like impurity centers, molecular complexes and electron delocalization in semiconductors (E.M. Gershenzon, A.P. Mel'nikov and R.I. Rabinovich). 7. Electron-electron interactions in the Anderson-localized regime near the metal-insulator transition (H. Kamimura). 8. Disorder and interactions in the system of quasi one-dimensional electrons (L.P. Gor'kov). Author index. Subject index.

927 citations

Journal Article
TL;DR: In this article, a simple model was used to allow for the influence of size quantization on interband absorption in a semiconductor sphere, and it was shown that the short-wavelength shift of the maximum of the absorption coefficient is proportional to h 2 /m e a 2, where m e is the electron mass.
Abstract: A very simple model is used to allow for the influence of size quantization on interband absorption in a semiconductor sphere. Expressions are obtained for the absorption coefficients of light in three limiting cases; when the radius of a semiconductor sphere a is less than the Bohr radii of electrons a, and holes a h ; when a h

369 citations


Cited by
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Journal ArticleDOI
26 May 2006-Science
TL;DR: In this paper, a single epitaxial graphene layer at the silicon carbide interface is shown to reveal the Dirac nature of the charge carriers, and all-graphene electronically coherent devices and device architectures are envisaged.
Abstract: Ultrathin epitaxial graphite was grown on single-crystal silicon carbide by vacuum graphitization. The material can be patterned using standard nanolithography methods. The transport properties, which are closely related to those of carbon nanotubes, are dominated by the single epitaxial graphene layer at the silicon carbide interface and reveal the Dirac nature of the charge carriers. Patterned structures show quantum confinement of electrons and phase coherence lengths beyond 1 micrometer at 4 kelvin, with mobilities exceeding 2.5 square meters per volt-second. All-graphene electronically coherent devices and device architectures are envisaged.

4,848 citations

Journal Article
TL;DR: The transport properties, which are closely related to those of carbon nanotubes, are dominated by the single epitaxial graphene layer at the silicon carbide interface and reveal the Dirac nature of the charge carriers.
Abstract: Ultrathin epitaxial graphite was grown on single-crystal silicon carbide by vacuum graphitization. The material can be patterned using standard nanolithography methods. The transport properties, which are closely related to those of carbon nanotubes, are dominated by the single epitaxial graphene layer at the silicon carbide interface and reveal the Dirac nature of the charge carriers. Patterned structures show quantum confinement of electrons and phase coherence lengths beyond 1 micrometer at 4 kelvin, with mobilities exceeding 2.5 square meters per volt-second. All-graphene electronically coherent devices and device architectures are envisaged.

4,578 citations

Journal ArticleDOI
TL;DR: In this article, the most characteristic properties of spin glass systems are described, and related phenomena in other glassy systems (dielectric and orientational glasses) are mentioned, and a review summarizes recent developments in the theory of spin glasses, as well as pertinent experimental data.
Abstract: This review summarizes recent developments in the theory of spin glasses, as well as pertinent experimental data. The most characteristic properties of spin glass systems are described, and related phenomena in other glassy systems (dielectric and orientational glasses) are mentioned. The Edwards-Anderson model of spin glasses and its treatment within the replica method and mean-field theory are outlined, and concepts such as "frustration," "broken replica symmetry," "broken ergodicity," etc., are discussed. The dynamic approach to describing the spin glass transition is emphasized. Monte Carlo simulations of spin glasses and the insight gained by them are described. Other topics discussed include site-disorder models, phenomenological theories for the frozen phase and its excitations, phase diagrams in which spin glass order and ferromagnetism or antiferromagnetism compete, the Ne\'el model of superparamagnetism and related approaches, and possible connections between spin glasses and other topics in the theory of disordered condensed-matter systems.

3,926 citations

Journal ArticleDOI
TL;DR: Nanocrystals (NCs) discussed in this Review are tiny crystals of metals, semiconductors, and magnetic material consisting of hundreds to a few thousand atoms each that are among the hottest research topics of the last decades.
Abstract: Nanocrystals (NCs) discussed in this Review are tiny crystals of metals, semiconductors, and magnetic material consisting of hundreds to a few thousand atoms each. Their size ranges from 2-3 to about 20 nm. What is special about this size regime that placed NCs among the hottest research topics of the last decades? The quantum mechanical coupling * To whom correspondence should be addressed. E-mail: dvtalapin@uchicago.edu. † The University of Chicago. ‡ Argonne National Lab. Chem. Rev. 2010, 110, 389–458 389

3,720 citations

Journal ArticleDOI
TL;DR: In this paper, ultrathin epitaxial graphite films were grown by thermal decomposition on the (0001) surface of 6H−SiC, and characterized by surface science techniques.
Abstract: We have produced ultrathin epitaxial graphite films which show remarkable 2D electron gas (2DEG) behavior. The films, composed of typically three graphene sheets, were grown by thermal decomposition on the (0001) surface of 6H−SiC, and characterized by surface science techniques. The low-temperature conductance spans a range of localization regimes according to the structural state (square resistance 1.5 kΩ to 225 kΩ at 4 K, with positive magnetoconductance). Low-resistance samples show characteristics of weak localization in two dimensions, from which we estimate elastic and inelastic mean free paths. At low field, the Hall resistance is linear up to 4.5 T, which is well-explained by n-type carriers of density 1012 cm-2 per graphene sheet. The most highly ordered sample exhibits Shubnikov−de Haas oscillations that correspond to nonlinearities observed in the Hall resistance, indicating a potential new quantum Hall system. We show that the high-mobility films can be patterned via conventional lithographic...

3,315 citations