The (100) surfaces of chromium and vanadium: Reconsiderations of their structure and reactivity

The structural properties of clean Cr(100) and V(100) surfaces have been examined by LEED, AES, Δφ and photoelectron spectroscopy with particular reference to the question of possible reconstruction. When clean, both surfaces exhibit (1 × 1) periodicity at 300 K. The c(2 × 2) phase on Cr(100) is associated with small amounts of adsorbed carbon and oxygen, and the (5 × 1) phase on V(100) is induced by subsurface oxygen. The nature of the V(100)?(5 × 1) surface was examined in detail by studying oxygen and bromine chemisorption on the (1 × 1) and (5 × 1) surfaces respectively. The surface → bulk transport of oxygen and the low pressure oxidation of V are characterised; a convenient spectroscopic method for detecting low levels of oxygen in vanadium is described. Electronic and structural aspects of the vanadium-bromine interaction are elucidated.