Halogen chemisorption, the pairwise diffusion of I, and trapping by defects on Si(100)

被引:17
作者
Xu, GJ
Signor, AW
Agrawal, A
Nakayama, KS
Trenhaile, BR
Weaver, JH
机构
[1] Univ Illinois, Dept Phys, Dept Mat Sci & Engn, Urbana, IL 61801 USA
[2] Univ Illinois, Frederick Seitz Mat Res Lab, Urbana, IL 61801 USA
基金
美国国家科学基金会;
关键词
thermal diffusion; scanning tunneling microscopy; Si(100); halogens; defects;
D O I
10.1016/j.susc.2004.12.026
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Halogen molecules dissociatively chemisorb on Si(100)-(2 x 1), and the bonding structures that they adopt can be elucidated with scanning tunneling microscopy. Of the Cl, Br, and I group, Cl has the highest single atom diffusion barrier, and both single and paired adatoms are observed at 295 K. The barrier is smaller for Br, and the adatoms can interrogate the surface until they form pairs, which are then immobile, or are trapped at C-type defects. The barrier is smallest for 1, allowing the formation of pairs and trapped states, but the pairs are mobile at ambient temperature. Their motion is thermally activated, the events are random, and the diffusivities along and across the dimer row are similar to0.42 and similar to0.17 Angstrom(2)/s at 295 K. The respective energy barriers for pairwise diffusion are similar to0.76 and similar to0.82 eV, assuming an attempt frequency of 10(12) s(-1). Studies over long times reveal that pairwise diffusion at low coverage is ultimately quenched by the increasing density of C-type defects, i.e. the increasing amounts of dissociated H2O. (C) 2005 Elsevier B.V. All rights reserved.
引用
收藏
页码:77 / 85
页数:9
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