The change of conductivity of erbium films caused by the sorption of hydrogen and oxygen

Abstract

Abstract Films of erbium were evaporated onto the inside wall of a pyrex glass reaction vessel at 1O−9 torr. Their mean thickness (200–600 A) was deduced from their mass and geometrical area. Estimates of their surface areas were made from the physical adsorption of krypton at 78 °K (BET method) giving a mean specific surface area of 71 m−2 g−1. The number of surface sites was calculated from a relationship given by Brennan et al.1). The sorption of hydrogen and oxygen was studied separately, by measuring the changes in the electrical resistance of the films as a function of the amount of pure gas admitted to the reaction vessel in measured doses ∼ 1018 atoms per dose. The experiments were repeated at 295 °K, 200 °K, 130–140 °K for both gases (measurements at 78 °K were not reproducible, probably because of a magnetic phase change). Hydrogen at 295 °K [as reported2)] caused an initial increase ΔR in the original resistance R to a maximum ΔR R ∼ 20 %, which was followed by a decrease to ΔR R = 0 and then to ΔR R A similar pattern of resistance changes was observed at 200°K and 130–140°K with smaller changes of ΔR R , i.e. 16 % and 8 % respectively, but no significant differance in surface (θ) and bulk atomic ratios at which the maxima occurred, e.g. ΔR R was a maximum for 1.6⩽θ⩽1.9.