Surface Diffusion Anomaly near a Substrate Phase Transition: H onW(100)

Abstract

Using a linear optical diffraction method, we have experimentally studied the long predicted diffusion anomalous behavior for H/W(100) near the reconstructive phase transition of the W(100) substrate. This anomaly manifests itself in the form of a strong dip in the diffusion coefficient D at the transition temperature T(C). We interpret the strong reduction of D as a result of the diverging friction damping near the transition. The finite dip in D instead of a vanishing D at T(C) also demonstrates the importance of the non-Markovian (memory) deviation from the simple instantaneous damping picture.

Step effects on diffusion near a substrate reconstructive phase transition: H on W(100)

“…[7][8][9][10][11][12][13][14][15][16] It provides an ideal model system to investigate the effect of the substrate phase transition on surface diffusion. As reported in a recent Letter, 17 the H diffusion anomaly near the reversible phase transition of W͑100͒ from a (1ϫ1) disordered phase at high temperature to a c(2 ϫ2) phase at low temperature was clearly demonstrated by experiment, in qualitative agreement with the prediction of an earlier theoretical work. 1 Surface steps, even at low densities, can have a considerable effect on the surface diffusion process.…”

“…21 Step effects, which are unavoidable in any macroscopic measurement that probes an area containing a large number of steps, can sometimes mask the true surface diffusion process such as intrinsic terrace diffusion. In this paper, we therefore extend our earlier study of the H diffusion anomaly near the W͑100͒ substrate phase transition 17 to the stepped surface, in part to investigate possible step effects on the anomalous behavior of D near the phase transition.…”

“…Then, the results of H diffusion on a stepped W͑100͒ surface together with those for a flat surface will be presented. The results on the flat surface have been published in a recent Letter 17 and are included here for comparison. Diffusion both perpendicular and parallel to steps will be covered.…”

Anomalous Fast Dynamics of Adsorbate Overlayers near an Incommensurate Structural Transition

“…The temperature at which this transition occurs is close to the point at which the striped domainwall structure starts to melt. This increase in frictional damping of the overlayer motion from the critical fluctuations near a surface structural transition has also been predicted and observed for other systems [17,18]. In contrast, the mobility in the hexagonal phase [ Fig.…”

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

“…It is generally believed that steps slow down diffusion in its perpendicular direction, as shown directly by photoemission electron microscopy for potassium on a Pd͑111͒ surface 30,31 and by linearly optical diffraction method for CO on Pt͑111͒; 32,33 yet H diffusion on stepped W͑100͒ surface is hardly affected by the steps. 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.…”