OPTICAL-PROPERTIES OF AGGASE2 POLYCRYSTALLINE FILMS PREPARED BY FLASHEVAPORATION

Structural studies on AgGaSe2 films prepared in vacuum of 10(-4) Pa on to glass or quartz substrates by a flash evaporation technique and ann ealed at 573 K for 2 h show that these films were polycrystalline and exhibited tetragonal chalcopyrite structure with a strong (112) orient ation with a = 0.599 nm, c = 1.089 nm and (c/a) = 1.816. The optical c onstants (the refractive index n, the absorption index k and the absor ption coefficient alpha) of polycrystalline AgGaSe2 films were determi ned from spectrophotometric measurements of the transmittance and refl ectance carried out at normal incidence in the wavelength range 500-20 00 nm. Graphical representations of surface and volume energy loss fun ctions as well as the real optical conductivity as a function of photo n energy show the existence of three possible optical transitions corr esponding to 1.79, 1.95 and 2.2 eV respectively.