Article,
Coverage dependent surface diffusion of noble gases and methane on Pt(111)
Surf. Sci., 297 (1): 27 - 39 (1993)
DOI: DOI: 10.1016/0039-6028(93)90012-9
Abstract
The surface diffusion of krypton, xenon, and methane on the Pt(111)
surface was studied using laser induced thermal desorption (LITD)
techniques. The surface diffusion coefficient of krypton on Pt(111)
at 45 K decreased dramatically with coverage from to approximately
Similarly, the surface diffusion coefficient of xenon on Pt(111)
at 80 K decreased from to. The coverage-dependent surface diffusion
coefficients for the noble gases on Pt(111) were consistent with
attractive interactions between the adsorbed atoms and a multiple
site diffusion mechanism. In contrast, the surface diffusion coefficient
of methane on Pt(111) at 45 K was independent of surface coverage
at . This coverage independence indicated that latera interactions
between the adsorbed methane molecules did not influence the surface
diffusion process. Thermal desorption kinetics for krypton, xenon,
and methane on Pt(111) were determined using temperature programmed
desorption (TPD) experiments. Using the variation of heating rates
method, the desorption energies were for Xe/Pt(111), and Edes = 3.6
� 0.15 kcal/mol for CH4/Pt(111). The TPD peaks for krypton and xenon
on Pt(111) shifted to higher temperature versus initial coverage,
consistent with attractive interactions between the adsorbed atoms.
In contrast, the coverage-independent TPD peak temperature for methane
on Pt(111) provided further evidence for the absence of interactions
between the adsorbed methane molecules.
