Gas Adsorption Studies on the (100) Plane of Vanadium by Low-Energy Electron Diffraction

Abstract

Gas adsorption studies were conducted on the (100) plane of a vanadium single crystal using low-energy electron diffraction (LEED). The crystal was exposed to hydrogen and to oxygen, in the pressure range from 10−6–10−9 torr, with the substrate held at temperatures between 25°–1400°C. A procedure for cleaning the surface of vanadium is described. Several important conclusions were reached: (1) the adsorption of hydrogen is random, i.e., amorphous; (2) the adsorption of oxygen is ordered; a (1 × 1) structure is formed and the intensity of the (00) beam is substantially higher than that from the clean surface; (3) when the temperature of the oxygen adsorbed crystal is raised to 1100°C, a (2 × 2) structure is formed; (4) on further heating of the oxygen-adsorbed crystal to 1400°C, all structures due to oxygen disappear; (5) with prolonged heating satellite spots appear on the (00) and the (10) beams, and cannot be removed by heating or argon ion bombardment. Thermal faceting takes place, and patches of a crystalline solid solution of tantalum (from the crystal support) and vanadium appear to form.