We measured the diffusion rate of deuterium on Ni(111) as a function of temperature at atomic coverage of θ=0.3 and 0.05. In both cases, the crossovers from classical over-barrier hopping to under-barrier tunneling occurred at around T=125 K. At T=110 K, we measured the tunneling diffusion rates Dtunnel(θ) for both deuterium and hydrogen in the coverage range from θ=0.05 to 0.45 and found that (1) Dtunnel(θ) varied by less than a factor of 3; (2) the overall features of Dtunnel(θ) for the two isotopes were similar; (3) Dtunnel(θ) weakly peaked at around θ=0.25 and 0.5. Our results mostly agree with an early report by Lin and Gomer. Based on these results, we discuss the effect of the hydrogen-hydrogen interaction on hydrogen tunneling diffusion on Ni(111).
ASJC Scopus subject areas
- Condensed Matter Physics