Thermal chemistry of CH3 on Si/Cu(100)

Citation
J. Han et al., Thermal chemistry of CH3 on Si/Cu(100), J PHYS CH B, 104(14), 2000, pp. 3078-3084
Citations number
21
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF PHYSICAL CHEMISTRY B
ISSN journal
15206106 → ACNP
Volume
104
Issue
14
Year of publication
2000
Pages
3078 - 3084
Database
ISI
SICI code
1520-6106(20000413)104:14<3078:TCOCOS>2.0.ZU;2-9
Abstract
Photoelectron spectroscopy (PES), thermal programmed desorption (TPD) studi es, and scanning tunneling microscopy (STM) investigated the interaction an d chemistry of CH3 (generated by the thermal cracking of azomethane) on Si/ Cu(100). Si was deposited on Cu(100) by the thermal decomposition of SiH4 a t 420 K. STM of adsorbate-free Si/Cu(100) at a less than saturation coverag e of Si revealed a surface that contained large domains of a Cu2Si structur e. These Cu2Si domains coexisted with regions that were believed to be lowe r in fractional Si coverage. TPD results showed that (CH3)(3)SiH desorbed n ear 200 K from CH3/Si/Cu(100) prepared with a low Si concentration. With in creasing Si concentration a (CH3)(3)SiH desorption state appeared near 420 K, in addition to the 200 K state. The two observed TPD states of (CH3)(3)S iH at 200 and 420 K were believed to be due to the thermal reaction of CH3 with the low Si density and high Si density (i.e., Cu2Si) regions, respecti vely. At a saturation coverage of Si, when the well ordered Cu2Si phase cov ered the surface, only the 420 K peak was present during CH3/Si/Cu(100) TPD . Results also suggested that (CH3)Si and possibly some (CH3)(2)Si intermed iates predominated on the surface below room temperature, and (CH3)(3)-Si s pecies were formed on the surface only at temperatures between 250 and 390 K. Surface hydrogen needed for the final evolution of (CH3)3SiH was generat ed from methyl groups at temperatures above 390 K on the Si-saturated Cu(10 0).