Diffusion of Hydrogen in Pd Assisted by Inelastic Ballistic Hot Electrons

TL;DR

This paper explains how inelastic ballistic hot electrons influence hydrogen diffusion in palladium, revealing that s-band electrons drive the process and account for experimental symmetry observations.

Contribution

It introduces a model combining ballistic electron microscopy and electron-phonon scattering to explain hydrogen diffusion driven solely by s-band electrons.

Findings

Hydrogen diffusion is driven by s-band electrons.

The model explains the symmetry in diffusion rates for positive and negative voltages.

Inelastic ballistic electrons significantly influence hydrogen mobility in Pd.

Abstract

Sykes {\it et al.} [Proc. Natl. Acad. Sci. {\bf 102}, 17907 (2005)] have reported how electrons injected from a scanning tunneling microscope modify the diffusion rates of H buried beneath Pd(111). A key point in that experiment is the symmetry between positive and negative voltages for H extraction, which is difficult to explain in view of the large asymmetry in Pd between the electron and hole densities of states. Combining concepts from the theory of ballistic electron microscopy and electron-phonon scattering we show that H diffusion is driven by the $s$-band electrons only, which explains the observed symmetry.