Spectroscopic Investigations of Problems in Thin Film Materials Chemistry

这个项目是在分析和表面化学的一般领域和在薄膜材料的子领域。虽然薄膜是一类非常有趣和重要的材料，但目前针对薄膜的化学分析技术还不充分。在这项研究活动中，Bohn教授和他的学生将在国家科学基金（NSF）资助CHE-8508722的基础上，将非经典激发现象用于5埃至5微米尺度的薄膜光谱学。这将通过两个独立的研究重点来实现。其中，砷化镓和铝取代砷化镓异质结构将被用作介质光波导，在光子能量低于III-V带隙的情况下进行频率调制截面测量。由于高纯度III-V半导体的亚带隙能区杂质相关跃迁的横截面非常弱，因此吸收测量需要光波导中的长路径。在第二个推力中，分子单层的结构-功能关系将在介电表面进行研究。这项工作的一部分将使用表面等离子体介导的光学二次谐波产生和高精度反射率测量来跟踪单层形成的动力学。此外,Bohn教授实验室对介电表面单分子层拉曼散射的检测能力将用于在超分子水平上探索吸附质分子结构与薄膜结构之间的关系。​本研究对III-V半导体器件的重要技术领域产生了广泛的影响。这些研究有望产生表征痕量杂质的新技术，从而确定高纯度半导体的行为。此外，这项工作将有助于加强对这些材料界面结构的理解，并深入了解这些多层分子结构的形成动力学，这对电子工业至关重要。

This project is in the general area of analytical and surface chemistry and in the subfield of thin film materials. Although thin films comprise an extremely interesting and important class of materials, techniques for chemical analysis which are specific to thin films are currently inadequate. In this research activity, Professor Bohn and his students will build on their progress under NSF grant CHE-8508722 to extend the use of nonclassical excitation phenomena for optical spectroscopy in thin films at size scales from 5 angstroms to 5 micrometers. This will be accomplished by pursuing two separate research thrusts. In one, gallium arsenide and aluminum-substituted gallium arsenide heterostructures will be used as dielectric optical waveguides to perform frequency modulated cross section measurements at photon energies just below the III-V bandgap. The absorption measurements require the long pathlengths available only in optical waveguides, because the cross sections of the impurity related transitions in the sub-bandgap energy region of high purity III-V semiconductors is extremely weak. In the second thrust, structure-function relationships in molecular monolayers will be examined at dielectric surfaces. A portion of this effort will use surface plasmon mediated optical second harmonic generation and high precision reflectivity measurements to follow the dynamics of monolayer formation. Additionally, the capability for examining Raman scattering from molecular monolayers on dielectric surfaces that is resident in Professor Bohn's laboratory will be used to probe the relationship between adsorbate molecular structure and film architecture on the supermolecular level. This research impacts broadly on the technologically important area of III-V semiconductor devices. These studies are expected to yield new techniques for the characterization of trace impurities that determine the behavior of high purity semiconductors. Additionally, this work should lead to an enhanced understanding of the interfacial structure of these materials and to insights into the dynamics of formation of these multi-layered molecular structures which are of prime importance to the electronics industry.