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Development of a time-resolved measurement method for detecting surface dynamic processes of epitaxial growth and studies on surface migration of reaction species.

开发用于检测外延生长表面动态过程的时间分辨测量方法并研究反应物质的表面迁移。

基本信息

批准号：
04402017
负责人：
ZAIMA Shigeaki
金额：
$ 16.19万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (A)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

项目摘要

The purpose of this work is to study dynamic processes of epitaxial film growth at gas-solid interfaces in an atomistic scale, such as surface migration of reaction species and surface segregation of atoms, and to develop a method for controlling surface reaction.It has been made clear the influence of Ar^+ laser irradiation in growth processes for epitaxial growth of Si/Si and Ge/Si by gas source molecular beam epitaxy. We can detect an effect of surface excitation on growth processes by Ar^+ laser irradiation because Si_2H_6 and GeH_4 molecules are not excited or dissociated by Ar^+ laser light. Characteristic features observed in this experiment are an increase in growth rates and a lowering of the substrate temperature that the intensity oscillation of reflection high energy electron diffraction (RHEED) is vanished. The increase in growth rates can be explained by an increase in adsorption sites of reaction species due to photo-desorption of hydrogen atoms adsorbed on surfaces. The vanishment of the intensity oscillation of RHEED means that the growth by step flows is promoted by an enhancement of surface atomic migration due to the photo-desorption of adsorbed hydrogen.The surface segregation of Ge atoms in Si/Ge_n/Si systems is also examined, in which the n is changed from 1 to 6. It can be found that a decay length of surface Ge concentrations in gas source MBE is lowered by 1/2-1/8 compared with that in conventional MBE.The mechanism of surface segregation is explained by the two-site exchange model, and it is considered that an apparent change in free energy due to segregation is lowered by the termination of surface dangling bonds with hydrogen atoms.In conclusion, we can clarify the role of hydrogen atoms on dynamic surface reaction processes such as surface migration and surface segregation and the possibility of controlling the surface reaction.

本工作的目的是在原子尺度上研究气固界面外延薄膜生长的动力学过程，如反应物种的表面迁移和原子的表面偏析，并开发一种控制表面反应的方法。明确了Ar~+激光辐照对气源分子束外延Si/Si和Ge/Si外延生长过程的影响。由于Si_2H_6和GeH_4分子不被Ar~(++)激光激发或解离，因此我们可以通过Ar~(++)激光照射探测到表面激发对生长过程的影响。实验中观察到的特征是生长速度加快，衬底温度降低，反射高能电子衍射(RHEED)的强度振荡消失。生长速度的提高可以用吸附在表面的氢原子的光解吸增加了反应物种的吸附位置来解释。研究了Ge原子在Si/Ge_n/Si系统中的表面偏析，发现气源分子束外延的表面Ge浓度衰减长度比传统分子束外延的表面Ge浓度衰减长度降低了1/2~1/8。表面偏析的机理用双位交换模型解释。并认为氢原子与表面悬挂键的终止降低了表面偏析引起的自由能的明显变化，从而阐明了氢原子在表面迁移、表面偏析等动态表面反应过程中的作用以及控制表面反应的可能性。