原子氢在Si(100)表面吸附的FI-STM研究

FI-STM INVESTIGATION OF ATOMIC HYDROGEN ADSORPTION ON THE Si(100)2×1 SURFACE

高性能的场离子-扫描隧道显微镜(field ion-scanning tunneling microscope简称FI-STM)已成功地用于原子氢在Si(100)2×1表面的化学吸附过程的研究。结果表明,在小于6L低的氢暴露量下,氢原子通常是吸附在Si的二聚原子列(dimer rows)的顶部。随着氢暴露量的增加,先后出现Si(100)2×1:H单氢化物相(monohydride)和Si(100)1×1::2H双氢化物相(dihydride)两种表面结构。氢饱和的Si表面的热脱附研究表明,当样品被加热到590K时,表面结构并无明显变化;而到达670K时,则表面的(1×1)双氢化物相消失;当温度升高到730K时,(2×1)结构的二聚原子列又重现于表面,而且在Si衬底的台阶上出现许多错列的吸附原子链。这些原子链垂直于原先的Si的二聚原子列的方向,因此被认为是由Si的氢化物热解产生的Si原子在Si(100)表面的有序化排列。

We have successfully observed the chemisorption of atomic hydrogen on Si (100)2×1 surface at room temperature by our high performance FI -STM (field ion—scanning tunneling microscope). Results showed that at low exposure of hydrogen (less than 6L),usually the hydrogen atoms adsorb at the side of the dimer rows. With increasing the exposure of hydrogen, the monohydride phase Si(100)2×1: H and dihydride phase Si(100)1×1∷ 2H occurred respectively. Desorption of the Si surface saturated by hydrogen showed that annealing at 590K resulted in no obvious changes in the surface structure, while at 670K, the surface becomes disordered, the (1×1) structure is eliminated. When the temperature rise to 730K,the (2×1) structure with missing dimer rows occurred again, and some adatom chains appeared on the Si substrate terraces. We attribute these adatom chains to Si atoms which formed by dissociation of the Si—H compounds on the Si surface, and because of the mobility of just dissociated Si atoms is high enough, so that the Si atoms can combine each other and form a new atomic chains perpendicular to the direction of the original dimer rows of the Si substrate. It is. in fact, an ordering process of the nascent Si atoms on the Si(100) surface.