Optical properties of bismuth oxide thin films prepared by reactive d.c. magnetron sputtering onto p-GaSe (Cu) [Articol]

Abstract

Bismuth oxide (Bi2O3) thin films with thickness in the range 20 – 160 nm have been deposited by d.c. reactive magnetron sputtering of Bi in an atmosphere Ar : O2 (1 : 1), onto single crystalline p-GaSe (Cu) substrates. The optical constants, n and k, of oxide films have been determined from the analysis of the polarization ellipse of the reflected radiation from outer surface of Bi2O3/p-GaSe structures. In the wavelength range 400 – 800 nm the refractive index of nanometric Bi2O3 films onto GaSe(Cu) decreases from 2.10 to 1.78 and it seen to in- crease at decreasing sample thickness. In order to determine the interaction mechanism between semiconducting oxide film and GaSe surface, the spectral characteristics of photocurrent through Bi2O3/p-GaSe junc- tion and optical absorption in the range 400 – 800 nm have been examined. As resulted from respective analyses, Bi2O3 film generates new valence bonds, which contribute to the in- crease in the density of localized states at Bi2O3/p-GaSe (Cu) junction interface.