Structural, Optical and Electrical Properties of In Doped CdS Thin Films Prepared from Co-Sputtering Technique

摘要

In-doped CdS thin films of 200 nm thickness has been prepared by co-sputtering of CdS and In ceramic target on glass substrates at 250 °C for a window layer of solar cells. The CdS and In targets were put in different gun whereas the In concentration in CdS thin films was varied by changed the RF power ranging from 5 watts to 40 watts. The RF power for CdS thin films was fixed at 40 watt for all the films. Optical, Structural, and electrical properties of CdS:In thin films have been investigated by UV-Vis spectrometry, X-ray diffraction (XRD), variable pressure scanning electron microscopy (VPSEM), and Hall Effect measurement. The XRD patterns showed that the films were hexagonal (wurtzite) structure having strong preferential orientation along the (002) plane and as the In concentration increased, the peak at (002) preferred orientations of the films are shifted a little from left to right side and films converted to amorphous form. The grains of the films were observed irregular in shape and randomly oriented spread all over the surface. The electrical conductivity, carrier concentration and Hall mobility increased with increasing In concentration at certain limits and then decreased with a further increase of In concentration. The optical band gap increased with increasing of In as well as electron concentration due to the increase of the Fermi level in the conduction band. But, as like Hall Effect data, the band gap also decreases after a certain limit of In concentration. The highest band gap 2.60 eV as well as highest carrier concentration 50.7×1018 cm~(-3) with resistivity 10.67 × 10~(-1) Ω-cm observed for the film of In RF power 10 watt and lowest band gap 2.25 eV was observed for the films of In RF power 40 watts.