Photoinduced changes in amorphous P-Se thin films

Photoinduced changes in the optical properties of normal (0 ° ) and oblique (80 ° ) incidencedeposited amorphous tetraphosphorus decaselenide (a-P4Se10) films have been investigated. The photo-induced effects are negligible in 0 °-films. Oblique deposition creates a low-density columnar microstructure which yields irreversible optical changes on illumination and annealing. Illumination of 80 °-films causes the shift of the absorption edge to longer wavelengths by 0.03 eV while annealing moves it towards shorter wavelengths by 0.06 eV. IR studies reveal the existence of three types of structural units in P4Se10 films whose relative concentrations change on exposure and on annealing. The results are supported by the observed chemical shift in the XPS core level spectra of P and Se