ABSTRACT

This study is geared towards using a novel single solid source precursor with metal organic chemical vapour deposition (MOCVD) technique in the temperature range of 370 to 470 ⁰C to grow copper zinc sulphide (CuZnS) thin films. The single solid source precursors were prepared by the direct reaction of ammonium morpholino-dithiocarbamate and the various metal chlorides solutions.      

Depositions of the ternary metal sulphide thus formed were carried out using Metal organic chemical vapour deposition (MOCVD) technique with nitrogen as the carrier gas at a flow rate of 2.0dm³ min^-1 for 2 hours. Characterizations of the deposited films were carried out using Infrared (IR) spectroscopy, X-ray Diffractometry (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX) Spectroscopy, Rutherford backscattering spectroscopy (RBS) as well as UV-Visible spectrophotometer. Four point probe was also used for the I-V characteristics of the films.

Experimental results revealed that some vibrational bands which were present on the IR spectra of the precursors could not be observed on the IR spectra of the corresponding copper zinc sulphide thin films which indicate a complete decomposition of the precursors. The structural analysis revealed that all the films were polycrystalline in nature with distinct peaks that has good adherence with the substrates. The RBS spectra revealed that the stoichiometry of the deposited films can be controlled by the deposition temperature and copper concentration. The optical characteristics exhibit high transmittance with a refractive index that increased with temperature. It also revealed a direct band transition films whose value decreased from 2.63 eV to 2.05 eV with deposition temperature (from 370to 470⁰ C). The variation of the optical band gap was due to the change in the crystalline sizes. The increase observed in electrical conductivity confirms the semiconducting property of the deposited films. The above findings showed that dithiocarbamate is suitable for preparing metal sulphides thin films particularly, copper zinc sulphide thin films.