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).