Morphology and structural studies of Ag photo-diffused GeySe1−y thin films prepared by RF-sputtering

Thin films of Ag photo-doped-GeySe1−y films were prepared by RF co-sputtering technique. A systematic study of the relation existing between the host layer composition and the saturation rate in silver was carried out. Morphology and composition studies before and after chemical etchings were performed by scanning electron microscopy and electron probe micro-analyses, respectively. Raman spectroscopy studies showed the presence of corner-sharing and edge-sharing Ge(Se1/2)4 tetrahedra in all thin films. The vibration mode corresponding to Sen-chains is observed for the Ge-poor host layer and on the contrary, Ge-rich thin films exhibited some tendency to form homopolar Ge–Ge bonds as a part of ethane-like Ge2Se6 units. These investigations revealed the amount of Ag that could be incorporated in the host layer. Such an amount strongly depends on the relative ratio Ge/Se in the GeySe1−y thin film. For the Ge-poor host layer, an incorporation of Ag (54 at.%) was observed but also a drastic increase in the film heterogeneity. On the other hand, the host layers with higher Ge content showed homogeneous surfaces and a saturation level of ∼32–41 at.% Ag.