Structural characterization of hot wall deposited cadmium selenide thin films

Abstract

Cadmium selenide (CdSe) films were prepared by the hot wall deposition technique with different quartz tube lengths under a vacuum of 6.6 mPa onto well cleaned glass substrates to optimize the tube length. The XRD analysis revealed that the films were polycrystalline in nature for smaller tube lengths and for smaller thicknesses, but with increasing thickness and increasing tube lengths a preferred orientation was observed on all substrates. The x-ray diffractograms of the films coated on 0.07 m length tube exhibit preferential orientation along the (103) direction for smaller thicknesses, which changes to the (002) direction as the thickness increases, but the films coated with other tube lengths show preferential orientation along the (002) plane parallel to the substrate at larger thicknesses. The lattice constants and the structural parameters viz., crystallite size (D), dislocation density and strain , were calculated for all the films and it was found that as the tube length increases the grain size and strain decreases up to 0.13 m tube length and increases for 0.15 m tube length. The effects of the substrate were studied by coating the film on steatite, mica and ITO substrates using an optimized tube length (0.15 m). Films coated on glass, mica and ITO have a very smooth surface finish, reflecting like a mirror, and those on steatite have a matt finish. Depending on the adhesiveness and grain size the substrates were chosen for further applications. Studies on the effect of substrate temperature were carried out on the films obtained using 0.15 m quartz tube length. From Rutherford backscattering spectrometry analysis, it was found that as the tube length increases the Cd/Se ratio approaches unity.