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

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Journal Title
Journal ISSN
Volume Title
School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2003
Major/Subject
Mcode
Degree programme
Language
en
Pages
075422/1-6
Series
Physical Review B, Volume 68, Issue 7
Abstract
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.
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Keywords
surface diffusion, hydrogen atoms
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Citation
Cai, Lei & Zheng, Chaozhi & Man, K. L. & Altman, M. S. & Granato, E. & Ala-Nissilä, Tapio & Ying, S. C. & Xiao, Xudong. 2003. Step effects on diffusion near a substrate reconstructive phase transition: H on W(100). Physical Review B. Volume 68, Issue 7. P. 075422/1-6. ISSN 1098-0121 (printed). DOI: 10.1103/physrevb.68.075422.