Deposition of CoxSy, NixSy MnS and CdS thin films from their alkylthiourea precursors using the Aerosol Assisted Chemical Vapour Desposition (AACVD) technique
Loading...
Date
2008
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Various complexes of Co (II), Ni (II), Mn (II) and Cd (II) thiourea and alkylthiourea have been successfully synthesized, using the 1:2 mole ratio metal salts of (NiCl^ C0CI2, MnCfe and CdCh) with their respective ligands. These complexes were characterized using melting points and elemental analysis to distinguish their monomelic character and confirm the purity of the complexes. Single X-ray crystal structures of [NiCl2(SC (NHC6Hn)2]2 and [MnCl2(CS(NH2)2)4] were obtained.
Thermogravimetric studies on each complex were conducted to elucidate their volatility, for the deposition of thin films. Their decomposition patterns were found to yield predominantly a 2-stage TGA profiles with the resultant leading to the formation of the respective metal sulfide. Thin films were successfully deposited via the single source precursor method on glass and GaAs substrates by the Aerosol Assisted Chemical Vapour Deposition (AACVD) technique. Their lower volatility nature yielded less uniform deposition of thin films such that the substrate was changed as well the suspension of the substrate on the stubs with improved uniformity of the thin film. The respective metal chalcogenide thin films deposited were characterized by X-ray Diffraction (XRD) for their crystallinity, Scanning Electron Microscopy (SEM) for their morphological properties, Ultraviolet (UV) - Visible (Vis) spectra for their optical properties and Energy Dispersive X-ray (EDAX) for the composition of the films. Thin film measurement was performed using the Interferometer method.
The X-ray diffraction pattern revealed different phases for the metal chalcogenide film, stoichiometric cobalt sulfide exhibited a mixture of cubic linnaeite C03S4 and cattierite C0S2, stoichiometric NiS, NiS2 (pyrite), |3- NiS (millerite), Ni3.xS2 and NiSi.97, Manganese sulfide revealed the presence of the a - alabandite phase and CdS showed the mixture of hexagonal and orthorhombic (300-350 C) and cubic phase at (400-450 C) respectively. Their morphological properties demonstrated the presence of mostly granulated spheres for the stoichiometric CoS, star-fish like rods for stoichiometric NiS, polycrystalline growth for the MnS films and mostly cubic and spore-like rods for CdS. Their absorption spectra revealed blue-shifted spectra with a mostly a higher optical band gap energy relative to that of bulk for all the metal chalcogenides. Thickness measurements showed that most thin films were deposited uniformly with minor contours and showed optimum adherence to the substrates.
Description
A dissertation submitted to the department of Chemistry, University of Zululand in fulfillment of the requirements of the Degree of Master of Science in Chemistry at the University of Zululand, 2008.
Keywords
Thiourea, alkylthiourea