Growth and optical absorption of thin ZnSe films

Abstract

ZnSe films 5 - 220 nm thick were deposited on high quality glass substrates by ebeam evaporation under ultrahigh vacuum conditions (base pressure 5 × 10-9 mbar). X-ray diffraction measurements have revealed a cubic fcc structure with strong {111} texture. Atomic Force Microscopy has shown the coexistence of large self-organized dots and small nanocrystallites. Light absorption spectroscopy in the ultraviolet-visible range allowed us to determine the optical band gap of the films at room temperature by the position of the absorption edge. This is found to be equal to the bulk value of 2.6 eV for most of the films. However, for very thin films (about 5-6 nm thick) a considerable blue shift of about 0.2 eV has been observed. © 2005 IOP Publishing Ltd.