Atomic and Electronic Structure Investigations of Adlayers on Semiconductors with Photoemission Holographic Imaging and Spectroscopy

9505618 Lapeyre本项目将使用同步辐射光发射光谱和其他电子能谱来研究半导体表面上覆盖层的结构和电子性质。重点将给予光电子衍射实验的性能，扫描的能谱可以反转，以获得三维图像的发光原子和它的近邻。反演是基于全息原理的类傅里叶变换，不需要任何外部输入即可获得图像。该技术已在包括Al， Ga， As和Se在内的各种系统上进行了演示。未来研究特别感兴趣的是影响半导体表面生长性质的结构变化——无论是同质外延还是异质外延——以及表面的电子特性。光发射全息术将应用于由不同吸附物组成的体系的结构测定，这些吸附物由Si、GaAs和ZnSe组成。全息技术的两种新应用将被开发：a)化合物半导体衬底上的单一吸附物，b)元素半导体衬底上的多重吸附物。一种新的原子级材料表征技术——光电全息技术正在被开发，并应用于与电子学和光电子学有很强技术相关性的材料的基础合成和加工研究。该计划的一个重要特点是培养学生在材料研究的一个基本的和技术上重要的领域。＊＊＊

9505618 Lapeyre This project will use synchrotron radiation photoemission spectroscopy and other electron spectroscopies to study the structure and electronic properties of overlayers on semiconductor surfaces. Emphasis will be given to the performance of photoelectron diffraction experiments where scanned energy spectra can be inverted to obtain three dimensional images of the photoemitting atom and its near neighbors. The inversion is a Fourier-like transform based on the holographic principle and does not require any external input to obtain an image. The technique has been demonstrated on various systems including Al, Ga, As and Se on Si surfaces. Of particular interest for future investigations are structural changes that influence the nature of growth--both homo- and hetero-epitaxy--at semiconductor surfaces and the electronic properties of surfaces. Photoemission holography will be applied to structure determination of systems composed of various adsorbates on Si, GaAs, and ZnSe. Two new applications of the holographic technique will be developed: a) a single adsorbate on a compound semiconductor substrate, and b)multiple adsorbates on an elemental semiconductor substrate. %%% A new atomic-level materials characterization technique, photoemisson holography, is being developed and applied to basic synthesis and processing research studies of materials with strong technological relevance to electronics and optoelectronics. An important feature of the program is the training of students in a fundamentally and technologically significant area of materials research. ***