Simultaneous Observation of Surface Processes under Exited Gas Phase Atmosphere Using Ion and Light Probes

在各种器件制造工艺中，通常采用化学气相沉积（CVD）或气源分子束外延（GSMBE）作为表面工艺，在逸出气相气氛中生长或蚀刻薄膜。虽然气相粒子（原子、分子、离子、等离子体）与材料表面的相互作用是这类制造的关键过程，但其原子尺度机制尚未完全阐明。这部分是由于缺乏适当的表面分析技术在退出气相气氛中是可行的。离子散射和反冲光谱（CAICISS/TOF-ERDA）和光衰减全反射红外光谱（ATR-FTIR）已被证明在表面过程的原位监测中是有用的，特别是用于确定表面氢原子的数量。在这个项目中，我们开发了一种利用离子和光探针同时观察出气相气氛下表面过程的新方法。其应用的最重要的结果是阐明了Ge/Si（001）氢表面活性剂介导的异质外延的生长过程，其中出射的原子氢作为表面活性剂被动态地提供给生长前沿。研究表明，在氢表面活性剂介导的异质外延中，(1)亚单层H原子很容易充当表面活性剂，(2)在最佳H覆盖范围之外，即使在生长前沿保持一氢化物相，表面也会发生粗糙化。

Thin film growth or etching in exited gas phase atmosphere is often performed as a surface process in various device fabrication procedures, where chemical vapor deposition (CVD) or gas source molecular beam epitaxy (GSMBE) is typically adopted. Although the interaction of gas phase particles (atoms, molecules, ions, plasma) with the surface of materials is a key process in such types of fabrication, its atomic-scale mechanism is not fully elucidated. This is in part due to the lack of appropriate surface analytical techniques feasible in exited gas phase atmosphere.Ion scattering and recoiling spectroscopy (CAICISS/TOF-ERDA) with ions and attenuated total reflection infrared spectroscopy (ATR-FTIR) with light have proven to be useful in in situ monitoring of surface processes, in particular, for the determination of the amount of surface hydrogen atoms. In this project, we have developed a novel method for simultaneous observation of surface processes under exited gas phase atmosphere using ion and light probes.The most significant result of its application is the elucidation of the growth process of Ge/Si(001) hydrogen-surfactant-mediated heteroepitaxy, in which exited atomic hydrogen is dynamically supplied to the growth front as a surfactant. It has been revealed that in the hydrogen-surfactant-mediated heteroepitaxy, (1) a submonolayer of H atoms readily acts as a surfactant, and (2) beyond an optimal H coverage, surface roughening occurs even though a monohydride phase is maintained at the growth front.