(Lecture on Feb. 14, 3-4pm, Glandt Forum, Singh Center for Nanotechnology)
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.