Optical properties of As2S3 layers deposited from solutions

Abstract This paper presents results of the preparation and optical characterization of As 2 S 3 layers by using spin or dip-coating technique and As 2 S 3 solutions in ethylenediamine and n-propylamine as solvents. These solutions were prepared from arsenic sulfide powders obtained from laboratory-prepared bulk glasses. Ethylenediamine and n-propylamine solutions with the same As 2 S 3 concentration of 0.7 mol/l were used for the layer preparation. Layers were prepared by both the dip-coating and spin-coating techniques with velocity of 0.2–30 cm/min and 2000 rpm for 90 s, respectively. Substrates used in these experiments were microscopic slides (refractive index of about 1.49). All applied As 2 S 3 layers were dried in vacuum for 60 min and then heat-treated at 180 °C for 60 s in nitrogen atmosphere. Prepared As 2 S 3 layers were characterized by transmission spectroscopy in the wavelength range of 200–100 nm. Thicknesses of applied layers in the range of 200–1500 nm and their refractive indices ranging from 1.7 to 2.3 at 800 nm were estimated from interference bands in measured transmission spectra using Swanepoel's method. Dispersion curves of the refractive index are shown in the paper. Optical band gaps of prepared layers in the range of 2.15–2.35 eV were determined from measured transmission spectra by using Tauc's extrapolation.