Step effects on diffusion near a substrate reconstructive phase transition

We have used the linear optical diffraction method to study the diffusion of hydrogen atoms on flat and stepped W(100) surfaces. At 0.17-monolayer (ML) H coverage, the diffusion coefficient (D) shows a strong anomalous dip at the substrate reconstructive phase transition temperature in an Arrhenius plot for diffusion on both surfaces. No anomalous diffusion behavior is observed at 1.2-ML H coverage on both surfaces in the entire range studied, 240-380 K, consistent with the absence of the phase transition at this H coverage. The strong reduction of D can be attributed to the diverging friction damping near the transition. Steps do not suppress the substrate phase transition and affect the diffusion anomaly very little. For both H coverages, the only effect of steps is to introduce a small Schwoebel-Ehrlich barrier (∼2.2 kcal/mol for 1.2 ML and ∼2.8 kcal/mol for 0.17 ML) near the step edges, which slows down H diffusion perpendicular to steps. Measurements of H diffusion parallel to steps reveals no obvious enhancement due to step edge diffusion.

DOI

10.1103/PhysRevB.68.075422

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Cai , L , Zheng , C , Man , K L , Altman , M S , Granato , E , Ala-Nissilä , T , Ying , S-C & Xiao , X 2003 , ' Step effects on diffusion near a substrate reconstructive phase transition : H on W(100) ' , Physical Review B , vol. 68 , no. 7 , 075422 , pp. 1-6 . https://doi.org/10.1103/PhysRevB.68.075422

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https://urn.fi/URN:NBN:fi:aalto-201805222596

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[article-cris] Perustieteiden korkeakoulu / SCI

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Step effects on diffusion near a substrate reconstructive phase transition

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