Ab initio investigation of lithium on the diamond C(100) surface

Abstract

We have performed ab initio calculations to investigate the adsorption of Li onto the clean and oxygenated diamond C(100) surface. Despite a large amount of interest in alkali-metal absorption on clean and oxidized semiconductor surfaces for both fundamental and technological applications, lithium adsorption on the diamond surface has not been reported. We find that Li adopts structures on the clean C(100) surface similar to those reported for Na, K, and Rb on diamond, though Li exhibits significantly higher binding energies in the range 2.7–3.1 eV per Li adsorbate. For the oxygenated C(100)-(1×1):O surface, the lowest energy involving a full Li monolayer structure shows an exceptionally large work-function shift of −4.52 eV relative to the clean surface, an effect similar to that seen for Cs O on diamond, but with a higher binding energy of 4.7 eV per Li atom. We propose that such a system, if verified by experiment, is suitable for the surface coating of diamond-based vacuum electronic devices, as it should exhibit higher thermal stability than the commonly used Cs O surface while retaining the advantage of a large lowering of the work function.