Tuesday, February 14, 2017
Glandt Forum (3rd Floor)
Singh Center for Nanotechnology
3205 Walnut Street, Philadelphia, PA 19104
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The properties of materials are in general determined by chemical composition and structure, but at the nanoscale they depend on size as well. As one or more dimensions of a material become increasingly smaller, not only can it inhabit ever smaller spaces; also its surface to volume ratio increases, and at a small enough size (typically well below 100 nm) a number of the material’s properties become governed by quantum mechanics. At this scale, non-intuitive phenomena like electronic quantum confinement and tunneling can become dominant and affect macroscopic properties such as optical absorption, electrical conductivity and chemical reactivity.
In this lecture, honoring Prof. Elias Burstein’s long life and extensive career in semiconductor physics, I will review some milestones of my own thirty-some-year nanoscience journey, with emphasis on those properties and applications that follow from confinement and tunneling. The first part of the talk will be centered on semiconductor-based nanostructures, with highlights of my work on the electronic properties of quantum wells and superlattices under electric fields and on resonant tunneling. I will pay special attention to the quantum-confined Stark effect and its application in electro-optic modulators; the Wannier-Stark ladder and its relation with quantum-cascade lasers; and the noise characteristics of electron tunneling, which allow to discriminate between different tunneling mechanisms. Because of the high degree of material perfection that it is possible to achieve in the epitaxial preparation of semiconductor nanostructures, to this day they serve as model systems for many nanomaterials of wide recent interest, including graphene and other two-dimensional materials.
In the second part of the talk, I will present a few examples of recent work at BNL, either by staff scientists or users of its facilities, in which the concepts of confinement and tunneling, combined with periodicity, are exploited in nanostructured surfaces with antireflection and water-repellent properties and in other artificial nanomaterials.
Emilio Mendez is Professor of Physics at Stony Brook University and Director of the Energy Science and Technology Department at Brookhaven National Laboratory.
Mendez holds a B.S. degree from Madrid’s Universidad Complutense and a Ph.D. in physics from the Massachusetts Institute of Technology. For fifteen years he worked at the IBM T. J. Watson Research Center as a research staff member, member of the strategic planning group and line manager. Since 1995 he is a Professor of Physics at Stony Brook University, where he has carried out research on nanomaterials and been deeply involved in undergraduate and graduate education. From 2006 to 2015 he was the Director of BNL’s Center for Functional Nanomaterials; since 2016 his management responsibilities at BNL have broadened, adding Materials Science, Chemistry, and Sustainable Energy Technologies to Nanoscience.
Throughout his career, Mendez’s research has focused on the discovery, understanding and application of novel semiconductor nanomaterials for optical and electronic devices. He is best known for his contributions to the physics of quantum wells and superlattices under an electric field, resonant tunneling, and the quantum Hall effects. He is the author of 6 patents and over 160 scientific publications. He has served in numerous national and international committees; currently, he is a member of advisory and review committees for several nanoscience centers and multinational programs.
For his scientific contributions, Mendez has been recognized with several honors and awards, including Fellowship to the American Physical Society, the 1998 Prince of Asturias Prize for Science and Technology, and the 2000 Fujitsu Quantum Device International Award.