Synthesis and characterization of spray pyrolised al-doped Cds thin films

Abstract

Aluminum doped cadmium sulfide (Cd,.,AI,S) thin films for different values of x (0.00- 0.18) have been prepared by spray pyrolysis technique on to glass substrates. In order to prepare Cd,.,AI,S thin films the 0.1 M aqueous solution of [Cd(CH]COOh.2H,O], [AI(CH]COO)j.2H:!O] and NH:!CSNH:!were used as the precursor solution. The surface morphology, structural, optical and electrica[ properties of the films Is studicd in details. The SFM micrographs of film show uniform surface. The Energy Dispersive X-ray (EDX) shows that films are stoichiometric. X-ray ditfraction (XRD) study shows that the grain size was varied from 22 nm to 29 nm with the increase in doping concentration of AI. Lattice constant also calculated from XRD data. All the samples have Polycrystalline Hexagonal crystal structure. The absorption coefficient (0:) of the (Cdi.,AtS) films was UV-VIS transmission spectra The optical spectra of Cdi.,AI,S ternary system exhibit high absorbance near ultraviolet rcgion and high transmission throughout thc visible and nearinfrared region (600-1100 nm). The direct band gap energies for thc films of dilTerent doping concentrations of Al were determined and found to bc 2.29-2.44 ev' The various optical parameters viz. EXlinction coefficient (k), Refractive index (n), Dielectric constant (E), Dielectric loss (0) and Optical conductivity (Il) have been measured from the optical data. Electrical paramcters like resistivity, conductivity, activation energy etc, of the Al doped CdS films were mcasured by the four probe method. Rcsistivity ofCd,.,AlxS has been measured for dilTerent doping concentrations in the tempcrature range of 320 to 430 K. The resistivity of Cd,.,A[,S films is found to decrease up to 350 K and after thaI it's becomc ~aturated. This behavior indicate> the scmiconductor nature of the films. The variation of conductivity of the films of different doping concentration with the increase in tempcrature is studicd. The Activation energy is found to be in the range of 0.245 to 0.368 for diff"rent concentration of f1[ms. The experimental results show that Al incorporation into the CdS enhances the photoconductivity and photosensitivity. The photoconductive Cd,.,AI,S thin films deposited by thc spray Pyrolysis technique is applicable for photodiodes, X-ray detectors and FET transistor, etc. Cd,.,A[,S thin films regarded as a prime candidate for solar cell fabrication because of large energy band gap, high refractive index, high optical absorption and also suitability of these films for various optoelectron ics applications.