Chlorine and iodine adsorption on the Ta(100) and Ta(110) surfaces

Abstract

The interaction of chlorine and iodine with the Ta(100) and Ta(110) surfaces, the two most densely packed bcc planes, has been investigated using LEED and Auger electron spectroscopy. Both halogens are readily adsorbed at room temperature. It appears that adsorption occurs dissociatively, via a mobile precursor state, with high initial sticking probability. LEED indicates that room temperature adsorption on the Ta(100) surface is disordered while both surfaces form series of temperature and coverage dependent phases above rom temperature. The decrease in work function noted during chlorine and iodine adsorption on the Ta(110) surface is discussed and compared with other halogen systems which show a similar unexpected decrease. Characteristic energy loss peaks in the region 8 to 50 V below the elastic peak have been investigated and peak assignments made for both clean and halogen covered surfaces.