Study of the correlation between structural and photoluminescence properties of CdSe thin films deposited by close-spaced vacuum sublimation

Abstract

CdSe polycrystalline films were deposited by a close-spaced vacuum sublimation method at different substrate temperatures (Ts) using glass slides as substrates. At Ts≤673K the films have a structure with strong dispersion of grain size (d) (from 0.1 to 0.3μm). In this case the layer-by-layer mechanism determines the growth process of the layers. For Ts=873K they have a columnar-like structure with a clear growth texture and the average grain size d=3–4μm. The films obtained at Ts>473K are n-type and only correspond to a single wurtzite phase. The crystallites are preferentially oriented with the (102) planes parallel to the substrate. At lower temperatures the films are bi-phase. The microstress level in CdSe films obtained at Тs=873K (0.5×10−3) is considerably smaller than for the films deposited at Тs=773K (4.0×10−3). Increase of the value of Ts improves the stoichiometry of CdSe films. Analysis of the low-temperature photoluminescence (PL) spectra let us determine the nature and energy of point and extended defects in the investigated films. It was shown that the films contain Na(Li) and P residual impurities. The results of the structural and PL measurements showed that the CdSe polycrystalline films are of fairly good crystal and optical quality for Ts=873K and can be suitable for various applications.