Anisotropic surface diffusion of CO on Ni(110)

Abstract

Anisotropic surface diffusion of CO on Ni(l 10) has been studied using the newly developed technique of optical second-harmonic diffraction from a laser-induced CO monolayer grating. Two distinct orthogonal diffusion channels, along [HO] and [001], were found. The measured diffusion coefficients yield the diffusion activation energies Ed(llO) = 1.1 ±0.2 kcal/mol and £^(001) =3.1 ±0.4 kcal/mol and the preexponential factors Z) 0 (lT0) =(3.8 ± 2.0) x 10 " 9 cm 2 /sec and Z) 0 (00l) = (4.8 ±4.4)x 10 " 6 cm 2 /sec. The anisotropy in the surface diffusion appears to cross over at T~~ 160 K.

Step effects and coverage dependence of hydrogen atom diffusion onPt(111)surfaces

“…[38][39][40] Here, we summarize the key points. First, a uniform hydrogen layer with a prescribed coverage is deposited at 100 K on a flat or a stepped Pt͑111͒ surface.…”

“…34,35 Thus, experiment on well characterized stepped Pt͑111͒ surfaces for H diffusion should be performed to quantitatively understand the influence of steps, and to experimentally test the tentative conclusion of Graham et al 1 In this paper, we present results of surface diffusion of H on stepped Pt͑111͒ surfaces, using linear optical diffraction (LOD), on vicinal Pt͑111͒ surface with specified miscuts. As shown for CO/ Pt͑111͒, 32,33,36,37 the linear optical diffraction technique [38][39][40] can be employed to study the step effects in both step-parallel and perpendicular directions. A number of advantages make the LOD technique particularly suited to study the step effects.…”

Low-energy electron microscopy of CO/Pt(111) surface diffusion by nonequilibrium coverage profile evolution

“…One method that is frequently used to prepare nonequilibrium coverage profiles is laser-induced thermal desorption ͑LITD͒. Many approaches have been taken to monitor profile evolution following LITD including hole refilling methods, 2-11 linear optical diffraction ͑LOD͒, [12][13][14][15] and photoemission electron microscopy ͑PEEM͒. [16][17][18] Low-energy electron microscopy ͑LEEM͒ has also been used to study surface diffusion indirectly by observing how some features at a surface change in response to mass transport under nonequilibrium conditions, e.g., step motion during island coarsening or growth, 19,20 domain evolution, 21 etc.…”

Combined Theoretical and Experimental Investigation of Mechanisms and Kinetics of Vapor-Phase Mercury Uptake by Carbonacoues Surfaces

“…Optical SHG can also be employed for study of surface diffusion on metal surface. (69,70) Adsorbate induced non-resonant reflectivity changes can probe adsorbate coverage on metal surfaces quantitatively. Optical differential reflectance (ODR) is an optical technique that has been applied to investigate adsorption and desorption on surfaces, resulting in estimation of coverage from optically determined film thickness.…”