Me. Castro et al., ADSORPTION AND DECOMPOSITION OF CF3I ON CLEAN AND IODINE-PRECOVERED AG(111), Journal of physical chemistry, 97(32), 1993, pp. 8476-8484
To enhance our understanding of the thermal interactions of fluorocarb
ons with transition-metal surfaces, CF3I was adsorbed on clean and iod
ine-precovered Ag(111) and studied by temperature-programmed desorptio
n (TPD), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelec
tron spectroscopy (UPS), and Auger electron spectroscopy (AES). On cle
an Ag(111) at 105 K, dissociative adsorption dominates at low coverage
s and molecular adsorption at high coverages. Dissociation involves C-
I bond cleavage; there is no evidence for C-F cleavage, even during TP
D. While multilayer desorption peaks near 118 K, chemisorbed CF3I deso
rbs in a sharp peak at 126 K with a high-temperature shoulder near 145
K. The only other detectable desorption products are CF3(g) and I(g),
which desorb at 300 and 830 K, respectively. In the presence of low c
overages of I(a), less CF3 and more CF3I desorbs. When the surface I/A
g ratio is 0.33 (square-root 3 X square-root 3 R30-degrees structure),
the dissociation channel is completely suppressed. The influence of a
tomic iodine is discussed in terms of combined electronic and site blo
cking effects.