Effect of Layer Thickness and Preparation Conditions on the Properties and Ethanol Sensitivity of ZnSe Thin Films

Nanocrystalline layers of ZnSe with thickness in the range 30-150 nm are deposited on Corning 7059 glass substrates at room temperature by thermal evaporation of ZnSe in vacuum. Periodically interrupted vapor deposition is used at various deposition rates. Some films are kept at ambient conditions for up to 60 days, others are annealed at 200° C and 400° C. X-ray diffraction, atomic force microscopy, spectroscopic ellipsometry are used to investigate structure, morphology and optical properties of the films. Ethanol sensing experiments are carried out at room temperature in air and the results show an increase of the layers sensitivity with decreasing thickness and deposition rate. The sensitivity behavior is related to films porosity.