Systematic Study of Electronic Phases, Band Gaps and Band Overlaps of Bismuth Antimony Nanowires

We have developed an iterative one dimensional model to study the narrow band-gap and the associated non-parabolic dispersion relations for bismuth antimony nanowires. An analytical approximation has also been developed. Based on the general model, we have developed, we have calculated and analyzed the electronic phase diagrams and the band-gap/band-overlap map for bismuth antimony nanowires, as a function of stoichiometry, growth orientation, and wire width

Frontiers of Material Research

(This information was taken from the Distinguished Scientist Lecture Series Program 1989-1990). Dr. Dresselhaus is currently Institute Professor at the Massachusetts Institute of Technology. She was formerly the holder of the Abby Rockefeller Mauze Chair in Electrical Engineering and in Physics at MIT. She is also affiliated with the Center for materials and Engineering, and with the Francis Bitter National Magnet Laboratory at MIT where some of the experimental work of her group is carried out. Dr. Dresselhaus holds professorships in MIT\u27s Department of Electrical Engineering and Computer Science and the Department of Physics. Dr. Dresselhaus was born in Brooklyn and recieved her A.B. from Hunter College in 1951, graduation Summa Cum Laude. From 1951 to 1952, she was a Fulbright Fellow at Newnham College, Cambridge University, and was awarded an A.M. from Radcliffe College in 1953. She received her Ph.D. from the University of Chicago in 1958. Dr. Dresselhaus was a NSF Postdoctoral Fellow at Cornell University from 1958-60, and Staff Member at the MIT Lincoln Laboratory from from 1967-70. She has traveled widley as a visiting professor, as a visiting professor, holding that position in the Department of Physics of the University of Campinas (Brazil), in the summer of 1971 as well as the physics departments of the Israel Institute of Technology in Haifa, Israel (1972), the Aoyama Gakuin Universityand Nihon University in Tokyo, Japan (1973), and the Instituto Venezolano de Investigaciones Ceintificas in Caracas, Venezuela (1977). Dr. Dresselhaus received many honorary degrees and awards, among them the Hunter College Hall of Fame Award in 1972, the MIT Killian Faculty Award in 1986, and the Annual Achievement Award from the Engineering Societies of New England in 1988. She was elected to the American Academy of Arts and Sciences (1974), the National Academy of Engineering (1974) and the National Academy of Science (1985). Dr. Dresselhaus was a member of the Committee on the Education and Employment of Women in Science and Engineering of the Commission on Human Resources, National Research Council, from 1975-77, and in 1984 served as President of the American Physical Society. She is a senior member of the Society of Women Engineers, and was elected member of the Harvard Alumni Board of Directors from 1974-77. She was on the editorial board of the Physical Review B from 1979-81. and in 1988 became a trustee of the Rensselaer Polytechnic Institute. Her Work: Dr. Dresselhaus has used and developed a wide range of techniques to study condensed matter physics, from microwave properties of superconductors to magnetic phases in semiconductors, and electronic structure of group V semimetals and graphite.https://digitalcommons.bard.edu/dsls_1989_1990/1001/thumbnail.jp

News and Views: Perspectives on Graphene and Other 2D Materials Research and Technology Investments

With the actual experimental realization of graphene samples, it became possible not only to exploit the special physical properties of graphene but also to exploit its technological applications. As the field developed, the discovery of other 2D materials occurred and this opened up access to a plethora of combinations of a large variety of electrical, optical, mechanical, and chemical properties. Now there are large investments being made around the world to develop the graphene research area and to boost graphene use in technology. Here, we discuss current research and some future prospects for this area of layered nanomaterials.Conselho Nacional de Pesquisas (Brazil) (Grant 551953/2011-0)National Science Foundation (U.S.) (Grants DMR-1004147 and DMR-1004147

Theory of Raman enhancement by two-dimensional materials: Applications for graphene-enhanced Raman spectroscopy

We propose a third-order time-dependent perturbation theory approach to describe the chemical surface-enhanced Raman spectroscopy of molecules interacting with two-dimensional (2D) surfaces such as an ideal 2D metal and graphene, which are both 2D metallic monolayers. A detailed analysis is performed for all the possible scattering processes involving both electrons and holes and considering the different time orderings for the electron-photon and electron-phonon interactions. We show that for ideal 2D metals a surface enhancement of the Raman scattering is possible if the Fermi energy of the surface is near the energy of either the HOMO or the LUMO states of the molecule and that a maximum enhancement is obtained when the Fermi energy matches the energy of either the HOMO or the LUMO energies plus or minus the phonon energy. The graphene-enhanced Raman spectroscopy effect is then explained as a particular case of a 2D surface, on which the density of electronic states is not constant, but increases linearly with the energy measured from the charge neutrality point. In the case of graphene, the Raman enhancement can occur for any value of the Fermi energy between the HOMO and LUMO states of the molecule. The proposed model allows for a formal approach for calculating the Raman intensity of molecules interacting with different 2D materials.National Science Foundation (U.S.) (Grant DMR-1004147)MIT-Brazil Collaboration progra

Resonant Tunneling and Intrinsic Bistability in Twisted Graphene Structures

We predict that vertical transport in heterostructures formed by twisted graphene layers can exhibit a unique bistability mechanism. Intrinsically bistable $I$-$V$ characteristics arise from resonant tunneling and interlayer charge coupling, enabling multiple stable states in the sequential tunneling regime. We consider a simple trilayer architecture, with the outer layers acting as the source and drain and the middle layer floating. Under bias, the middle layer can be either resonant or non-resonant with the source and drain layers. The bistability is controlled by geometric device parameters easily tunable in experiments. The nanoscale architecture can enable uniquely fast switching times.Comment: 7 pages, 4 figure

The Renaissance of Black Phosphorus

One hundred years after its first successful synthesis in the bulk form in 1914, black phosphorus (black P) was recently rediscovered from the perspective of a two-dimensional (2D) layered material, attracting tremendous interest from condensed matter physicists, chemists, semiconductor device engineers and material scientists. Similar to graphite and transition metal dichalcogenides (TMDs), black P has a layered structure but with a unique puckered single layer geometry. Because the direct electronic band gap of thin film black P can be varied from 0.3 to around 2 eV, depending on its film thickness, and because of its high carrier mobility and anisotropic in-plane properties, black P is promising for novel applications in nanoelectronics and nanophotonics different from graphene and TMDs. Black P as a nanomaterial has already attracted much attention from researchers within the past year. Here, we offer our opinions on this emerging material with the goal of motivating and inspiring fellow researchers in the 2D materials community and the broad readership of PNAS to discuss and contribute to this exciting new field. We also give our perspectives on future 2D and thin film black P research directions, aiming to assist researchers coming from a variety of disciplines who are desirous of working in this exciting research field.Comment: 23 pages, 6 figures, perspective article, appeared online in PNA