Spectroscopy of Coulomb Interactions in Disordered Electronic Solids

点击翻译按钮获取中文摘要

w:\awards\awards96\num.doc 9700482 Lee This experimental research project focuses on elucidating Coulomb interaction effects in disordered electronic solids. The project will concentrate on doped silicon, but will include work on quasicrystals and perovskites. Three complementary spectroscopies will be used. First, previous work on electron tunneling measurements of the single-particle density of states will be extended down to 0.1K and to more insulating materials, where observation of strong interaction effects such as multiple- electron excitations and spin correlations will be possible. Second, noise spectroscopy will be pursued to characterize the random charge fluctuations in disordered solids.. Third, the finite frequency electrical conductivity will be measured through the microwave regime (0.05 to 20 GHz) in order to probe the transport density of states. This frequency range is of particular interest because some existing DC conductivity results suggest the presence of a correlation gap of width 8 to 12 GHz. %%% This experimental research project uses three complementary techniques to study the effects of the Coulomb forces between electrons, and between electrons and charged impurities, on the conduction behavior of disordered electronic conductors, with some emphasis on the important semiconductor silicon. Electrical conduction in silicon results in part from dopant atoms which contribute a free carrier, and in this process the impurity site also becomes charged. The random distribution of the charged impurity sites alters the motion of the free carriers in ways that are of interest in this study. Experimental techniques include electron tunneling spectroscopy, electrical noise measurement, and finite frequency conductivity measurements. Results from this research may include unusual new effects or m aterials which may find new application in technology. This research project is interdisciplinary in nature and involves both graduate and undergraduate students who will be excellently trained to enter positions in industry, government or education. ***