Strong quantum confinement effects in thin zinc selenide films

Thin Zinc Selenide films in the thickness range 3-50 nm have been prepared on high quality glass substrates by e-beam evaporation under ultrahigh vacuum conditions. Optical absorption spectroscopy experiments reveal a systematically increasing blue shift of the effective bandgap energy as the film thickness decreases, reaching a maximum value of 0.32 eV for the thinner film. The experimental results, which indicate the presence of strong quantum confinement effects, are fairly well described by theoretical calculations based on the potential morphing method, using as a confining potential the finite square well potential with height of the barriers equal to 5 eV.