The random fluctuations (noise) of the electricity that flows through a conductor often give information that is veiled when only the average current is known. By better understanding how materials conduct electricity it becomes possible to determine the ultimate limits of today's devices and to design future ones with improved characteristics. The goal of this project is to elucidate the mechanisms of electronic conductance in materials of fundamental and technological importance, by studying experimentally their electronic noise. The focus is on atomically thin carbon sheets (graphene) and on semiconductor multi-layer nanostructures, which have unique properties and high potential for nanoelectronic applications but whose properties are not well understood. This project aims to answer questions such as, Are all devices with the same macroscopic behavior alike, or can we differentiate among them and select the optimum one for a specific application? How much smaller can devices become before they are limited by the "personality" of individual electrons? By addressing these and similar questions, the students involved in this interdisciplinary project probe deep physics questions and experience the connection between science and technology; while learning versatile techniques of permanent value for careers in industry, academia or government.
This project aims at elucidating the mechanisms of electronic conductance in nanoscale structures by studying their intrinsic current fluctuations, or shot noise. The focus is on graphene and on semiconductor multi-barrier structures. Because of the atomic arrangement in graphene, the motion of its free electrons is quasi-relativistic, which gives rise to unique properties not well understood. Periodic semiconductor multi-barrier structures (superlattices) exhibit high-frequency oscillations that might lead to practical sources of terahertz radiation, but the mechanism for electron transport remains obscure. The project emphasizes noise measurements in those two paradigmatic materials at T = 4K and the comparison of results with existing theoretical predictions, to assess the validity the predictions. The project benefits from the collaboration with world leaders in carbon-based structures and in materials preparation techniques. The results of this project are expected to illuminate basic concepts that transcend the materials studied, and to help define the ultimate limits that current fluctuations impose on nanoscale devices. The students involved in this interdisciplinary project probe deep physics questions and experience the connection between science and technology; while learning versatile techniques of permanent value for very diverse careers.
