Reflection Microscope Study of Current Effects on Si surfaces

两年内取得的成果可分为两个专题。(1)金属原子在硅表面电迁移的观察;（2）清洁硅表面电流效应的观察。(1)研究了平行于电流的Ge表面电迁移和平行于电流但优先平行于表面原子台阶的Ag表面电迁移。对于Cu-Au的共吸附结构，ROO <3>xROO<3>结构，注意到直流电流引起的相分离。研究了Ag和In在Si（III）5x 5-Ge和Si（III）ROO <3>xROO<3>-Ag结构表面的电迁移，发现了由于改性引起的迁移特征的强烈影响。此外，迁移方向和光电发射的变化之间的密切相关性，由于额外的沉积的金属被发现。(2)众所周知，在Si（III）7 x7和1x 1之间的相变之上，升压DC电流引起表面台阶的规则阵列（R表面），而降压电流引起台阶聚束（B表面）。观察到当表面冷却至7 x7相时，该电流效应反转三次，即。例如，在升压电流作用下，当7 × 7结构出现在台阶外缘时，R面变为B面，当7 × 7结构区域覆盖40-50%以上的台阶时，R面又恢复到R面，当7 × 7结构区域覆盖80%以上的台阶时，R面最终变为B面。研究还发现，这些过程对台阶的性质有一定的依赖性，而台阶的性质与台阶自发形状起伏的相对强度密切相关。

Results obtained in two years can be classified into two topics. (1) Observations of Surface electromigration of metal atoms on Si surfaces and (2) observations of current effects on clean Si surfaces.(1) Surface electromigration of Ge parallel to the current and surface electromigration of Ag parallel to the current but preferentially parallel to surface atomic steps were studied. For co-adsorption structure of Cu-Au, ROO<3>xROO<3> structure, phase separation caused by DC current was noticed. Surface electromigration of Ag and In on modified surfaces such as Si(III)5x5-Ge and Si(III)ROO<3>xROO<3>-Ag structures was studied, and strong effect of migration features due to the modification was noticed. Also a close correlation between the migration direction and photoemission changes due to additional depositon of metals was found.(2) It was well known that above the phase transition between Si(III)7x7 and 1x1, a step-up DC current causes a regular array of surface steps (R surface) and a step-down current causes step bunching (B surface). It was observed that this current effect reverses three times when the surface was cooled to the 7x7 phase, i. e., under a step-up current, a R surface changed to a B surface when the 7x7 structure appear at outer edges of steps and returned to a R surface when the 7x7 structure cover more than 40-50% of the terraces, and finally changed into a B surface when the 7x7 structure regions covered more than 80% of the terraces. It was also found that such processes slightly depended on the character of the steps, which was closely related to relative strength of a spontaneous shape fluctuation of the steps.