US-Federal Republic of Germany Cooperative Research: Direct Imaging of Surface Phase Separation Using LEERM

该奖项支持Ellen D教授。威廉姆斯和博士。 马里兰州大学的Raymond Schuef与 Ernst G教授物理研究所的鲍尔 克劳斯塔尔技术大学，联邦共和国 德国，硅表面相分离的研究。 在马里兰州大学， 发现了与Si（111）相邻的表面， 使用低能电子衍射（LEED）表征。 对这一转变的一个典型描述是， 发达国家，但主要问题的机制，质量 运输仍然。 在克劳斯塔尔技术大学， 一种名为低能电子的新仪器 反射显微镜（LEERM）已经研制成功。 这 仪器可用于对表面进行真实的实时成像， 分辨率优于200埃。 是目前 世界上只有这样的乐器。 以前的实验 在马里兰州大学使用LEED进行的 在克劳斯塔尔重复使用LEERM。 硅表面 将在转变温度下成像， 相位中涉及的表面台阶的运动 可以直接观察到分离。 结果将 用于测试阶跃漂移的理论模型，表面 Si（111）表面的自扩散和能量学 重建 刻面是一种普遍的现象， 通过大规模的物质运输重新排列， 不同的方向。 刻面的出现是 在催化剂中很重要，它与催化剂相连 失活，也可能导致反应振荡 范围. 刻面也可能导致外延层的光滑度降低。 在生长过程中会退化。 最后 刻面的机制对于理解 表面粗糙度与附着力和润滑有关。 在制定详细的 过去20年来，由于缺乏对刻面的认识， 实验数据来支持理论推测。 这项工作提出了使用真实的时间成像， 在良好控制的条件下进行表面刻面。

This award supports Professor Ellen D. Williams and Dr. Raymond Phanuef of the University of Maryland to collaborate with Professor Ernst G. Bauer of the Physics Institute of the Technical University of Clausthal, Federal Republic of Germany, in a study of phase separation of silicon surfaces. At the University of Maryland, a phase separation of surfaces vicinal to Si(111) has been discovered and characterized using Low Energy Electron Diffraction (LEED). A thermodynamical description of the transition has been developed, but major questions about the mechanisms of mass transport remain. At the Technical University of Clausthal, a remarkable new instrument called the Low-Energy Electron Reflection Microscope (LEERM) has been developed. This instrument can be used to image surfaces in real time with better than 200 angstroms resolution. It is currently the only such instrument in the world. Experiments previously performed using LEED at the University of Maryland will be repeated using the LEERM at Clausthal. Silicon surfaces will be imaged at the temperature of the transition so that the motion of the surface steps involved in the phase separation can be observed directly. The results will be used to test theoretical models for step wandering, surface self-diffusion and the energetics of the Si(111) surface reconstruction. Faceting is a widespread phenomenon in which a surface rearranges via large scale mass transport to form planes of different orientations. The occurrence of faceting is important in catalysts, where it is linked to catalyst deactivation and also possibly to oscillations in reaction ranges. Faceting may also cause the smoothness of epitaxial interfaces to be degraded during growth. Finally, the mechanisms of faceting may be important in understanding surface roughness related to adhesion and lubrication. Little progress has been made in developing a detailed understanding of faceting in the past 20 years due to lack of experimental data to support theoretical speculations. This work proposes use of real time imaging to follow surface-faceting under well controlled conditions.