Optical properties of wide band gap indium sulphide thin films obtained byphysical vapor deposition

Thin films of indium sulphide containing oxygen have been synthesized follo wing a dry physical process. The constituents are deposited by thermal evap oration on glass substrates and then annealed under argon flow. Polycrystal line beta -In2S3 containing oxygen thin films are obtained as soon as the t emperature of annealing is between 623 and 723 K. In this paper, these beta -In2S3 thin films have optically been studied. The optical band gap is dir ect. Its value is not dependent on the temperature of annealing. It is abou t 2.8 eV, which is higher than that of beta -In2S3 single crystal. This hig h value is related to the presence of oxygen in the films. The extinction c oefficient ii and the refractive index n of the films have also been found independent of the annealing temperature. These optical properties make the films studied good candidates to be substituted to CdS in Cu(In,Ga)Se-2 ba sed solar cells.