Quenching of metal sticking by photo-oxidation of an amorphous semiconductor: Zn on GeS2

The sticking probability of Zn on amorphous GeS2 is greatly reduced when the UHV-prepared semiconductor film is photo-oxidized in the presence of band-gap radiation. The phenomena underlying this interesting effect have been elucidated in a kinetic and structural study using electron spectroscopy and x-ray-absorption spectroscopy. Selective photo-oxidation of Ge sites strongly suppresses the formation of Ge-Zn bonds at the interface: these act as nucleation sites for the growing metal film. A consistent picture emerges that also accounts for the very different behavior encountered during deposition of Ag films with and without photo-oxidation in the closely related Ag/GeS2 system.