Infrared spectra of ammonia adsorbed on evaporated germanium films
Abstract
The spectra due to various adsorbed species of ammonia have been obtained between 2000 and 1000 cm–1. A weak band at 1920 cm–1, which disappears with time or on continued exposure, has been attributed to surface Ge—H bonds resulting from dissociative adsorption. Two mechanisms have been postulated for the removal of adsorbed hydrogen; at low exposures surface recombination of pairs of H atoms is thought to be responsible, while at high exposures the mechanism NH3(g)+ Ge—H → Ge—NH2(g) is thought to be more relevant. Bands in the deformation region have been assigned to: adsorbed primary amine (1540 cm–1), co-ordinatively adsorbed ammonia (1590 cm–1 and 1320–1250 cm–1) and physically adsorbed ammonia (1650–1600 cm–1 and 1150–1000 cm–1). The reaction: Ge—O—Ge + NH3(g)→ Ge—OH + Ge—NH2 has also been inferred from spectra obtained with pre-oxidised germanium.