Anomalous desorption of H2 from TiHx films, 0.3 ≲x≲ 1.8

Abstract

UHV-prepared Ti films exposed to hydrogen at pressures of 10−6-10−5 Torr show unexpected desorption of H2 at room temperature. The desorption occurs only at average H/Ti atomic ratios x ≳ 0.3. A model is proposed that explains the desorption and well describes the absorption-desorption kinetics. The formation of a stable surface hydride at x ≈ 0.3 and a concentration dependent chemical potential for hydrogen in the surface hydride are important ingredients in the model.