The annealing behaviour of a Cs2O/GaAs(110) surface studied by electron spectroscopy

A Cs2O overlayer was prepared by simultaneous oxygen-caesium adsorption on GaAs(110) at room temperature. Electron spectroscopy has been used to inves tigate the CS2O/GaAs surface as a function of annealing temperature. The Cs 2O-covered GaAs surface exhibits metallic behaviour. The results show that x-ray irradiation transforms Cs2O into an O- species on the top surface and facilitates the interfacial reaction forming the Cs-O-Ga bond. In the temp erature range from 300 to 620 K, the decomposition of Cs2O caused by x-ray irradiation and annealing is accompanied by growth of the O-, Cs-O-Ga, Cs-O -As, As-O and Ga-O species as well as the desorption of Cs. For further ann ealing, oxygen bonded to caesium gradually transfers to Ga and As, leading to fast Cs desorption and the formation of Ga2O3 and As2O3. Meanwhile, the evaporation of As2O3 and the reaction between the As2O3 species and substra te GaAs to form Ga2O3 Occur.