First principles study of gallium cleaning for hydrogen-contaminated α-Al₂O₃(0001) surfaces

The use of gallium for cleaning hydrogen-contaminated Al₂O ₃ surfaces is explored by performing first principles density functional calculations of gallium adsorption on a hydrogen-contaminated Al-terminated α-Al₂O₃(0001) surface. Both physisorbed and chemisorbed H-contaminated α-Al₂O ₃(0001) surfaces with one monolayer (ML) gallium coverage are investigated. The thermodynamics of gallium cleaning are considered for a variety of different asymptotic products, and are found to be favorable in all cases. Physisorbed H atoms have very weak interactions with the Al ₂O₃ surface and can be removed easily by the Ga ML. Chemisorbed H atoms form stronger interactions with the surface Al atoms. Bonding energy analysis and departure simulations indicate, however, that chemisorbed H atoms can be effectively removed by the Ga ML.