Effect of Bath Temperature on the Optic Properties of Aluminium Sulphide Thin Films

Al2S3 thin films on glass substrate have been deposited by chemical bath deposition technique at temperatures 300K and 373K. Aqueous solution of 50ml containing AlCl3, Thiourea and EDTA, where AlS3 and thiourea were the sources of Al and S and EDTA was used as a complexing agent. Al2S3 films were prepared at various bath temperatures while the deposition period was kept fixed at 2 hours. The effect of the resulting film properties was studied by UV-VIS spectrophotometer. The optical absorption spectra of Al2S3 films showed that the optical absorption increases with the bath temperature while the transmittance decreases with increase in the bath temperature. The optical band gap was found to decrease from 1.80eV to 1.35eV, as the deposition temperature was increased from 300K to 373K.