Real Time Studies of the Evolution of Structural, Optical, and Electronic Properties in Thin Films

实时光谱椭偏法（SE）和偏振法，结合直接显微结构分析技术，将被用于表征薄膜的成核、聚结、生长过程以及光学性质。这里应用的SE技术是独一无二的，因为它们能够以单层灵敏度作为薄膜厚度的连续函数来确定光学特性和电子结构，这些薄膜是由工业中广泛使用的方法制成的，例如等离子体增强化学气相沉积和磁控溅射。本研究分为两个项目：(I)半导体薄膜的制备和研究这些薄膜从团簇到聚结阶段到持续生长过程中的尺寸效应；（ii）气体成分、衬底材料和衬底温度对金刚石薄膜中键合和结构演变的作用。所研究的材料体系在薄膜光伏器件、光子和电子发射器件以及光学和机械涂层中具有广泛的应用。因此，将在该项目和其他项目之间建立协同关系，以转移新的仪器设计、材料技术和人力资源。我们将研究在真空条件下由蒸气源形成的薄膜的原子层接层的生长过程。这类研究将利用新颖的高速测量技术，包括将偏振光射入反应器，从生长的薄膜表面反射，并检测反射时的偏振变化。这些技术提供了薄膜的厚度与原子层的灵敏度，薄膜的生长速度，和它的光学性质，其中后者包括折射率和吸收系数。要研究的薄膜包括用于光学和电子器件（如太阳能电池和发光二极管）的非晶和晶体半导体，以及用于光学、机械和电子发射涂层的金刚石。该项目有四个目标：(1)开发高灵敏度光学仪器；(2)更好地了解薄膜是如何生长的；(3)在此基础上优化薄膜的特定应用；(4)在该项目和其他行业项目之间建立协同关系，以转移新的仪器设计、材料技术和人力资源。＊＊＊

w:\awards\awards96\*.doc 9622774 Collins Real time spectroscopic ellipsometry (SE) and polarimetry, combined with microstructural analysis by direct techniques will be applied to characterize the nucleation, coalescence, and growth processes as well as the optical properties of thin films. The SE techniques applied here are unique in their ability to determine the optical properties and electronic structure with monolayer sensitivity as a continuous function of thickness for films fabricated by methods employed widely in industry, for example, plasma-enhanced chemical vapor deposition and magnetron sputtering. The research is divided into two projects: (I) the preparation of semiconductor films and the study of size effects in these films as they evolve from clusters through the coalescence stage to continuous growth, and (ii) the role of gas composition, substrate material, and substrate temperature on the evolution of bonding and structure in diamond films. The materials systems studied have a wide range of applications in thin film photovoltaic devices, photon and electron emission devices, and optical and mechanical coatings. As a result, synergistic relationships will be established between this program and other programs with industry for the transfer of new instrument designs, materials technologies, and human resources. %%% The growth of thin films under vacuum from vapor sources will be studied as they are formed, atomic layer-by-layer. Such studies will make use of novel, high-speed measurement techniques that involve directing a polarized white light beam into the reactor, reflecting it from the surface of the growing film, and detecting the change in polarization upon reflection. These techniques provide the thickness of the film with atomic layer sensitivity, the growth rate of the film, and its optical properties, t he latter including the index of refraction and absorption coefficient. The films to be studied include amorphous and crystalline semiconductors, with applications in optical and electronic devices such as solar cells and light-emitting diodes, and diamond with applications as optical, mechanical, and electron-emitting coatings. The program has four goals: (i) developing high sensitivity optical instrumentation, (ii) obtaining a better understanding of how thin films grow, (iii) optimizing thin films for specific applications based on this understanding, and (iv) establishing synergistic relationships between this program and other programs with industry for the transfer of new instrument designs, materials technologies, and human resources. ***