Spectroscopy of Coulomb Interactions in Disordered Electronic Solids

本实验研究项目的重点是阐明无序电子固体中的库仑相互作用效应。该项目将专注于掺杂硅，但也将包括准晶体和钙钛矿的研究。将使用三种互补光谱。首先，先前对单粒子态密度的电子隧穿测量将扩展到0.1K和更多的绝缘材料，在那里观察强相互作用效应，如多电子激发和自旋相关将是可能的。其次，将采用噪声光谱来表征无序固体中的随机电荷波动。第三，将通过微波频段（0.05 ~ 20 GHz）测量有限频率电导率，以探测态的输运密度。这个频率范围是特别有趣的，因为一些现有的直流电导率结果表明存在宽度为8至12 GHz的相关间隙。本实验研究项目采用三种互补的技术来研究电子之间以及电子与带电杂质之间的库仑力对无序电子导体导电行为的影响，重点研究了重要的半导体硅。硅中的导电部分是由于掺杂原子提供自由载流子，在此过程中杂质位点也带电。带电杂质位点的随机分布以本研究感兴趣的方式改变了自由载流子的运动。实验技术包括电子隧穿光谱、电噪声测量和有限频率电导率测量。这项研究的结果可能包括不同寻常的新效果或可能在技术上找到新的应用的新材料。这个研究项目是跨学科的，涉及研究生和本科生，他们将接受良好的培训，进入工业、政府或教育部门的职位。＊＊＊

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. ***