Influence of pH, Doping and Annealing on Structural and Optical Properties of Chemical Bath Deposited Cobalt (iii) Oxide (co3o4) Thin Films

Influence of PH, Doping and Annealing on Structural and Optical Properties of Chemical Bath Deposited Cobalt (iii) Oxide (co3o4) Thin Films

Abstract

Cobalt (III) oxide (Co3O4) thin films were deposited on glass substrates at a temperature of 70°C with continuous stirring and heating of the al kaline bath of various pH of 8, 10, 12 and 14. Cobalt (II) chloride hexahydrate (CoCl2•6H2O) was used as source of Co2+ and to make it alkaline, 25% aqueous ammonia solution was added as the complexing agent with constant heating and stirring. The bath was doped with zinc nitrate (Zn(NO3)2 and later, some samples were annealed at 200°C for 30 minutes. X-ray diffraction method was used to confirm the depositions. The structural features obtained from the x-ray diffraction showed the peaks of Co3O4 and increase in crystallinity as pH increases which was confirmed by SEM. It also shown improvement in crystallinity after doping and annealing. The optical studies showed a variation of absorbance, reflectance, direct band gap energy and refractive index as pH varies and changes after doping and annealing. The range of direct band gap energy and refractive index obtained are 1.34eV – 2.85eV and 1.38 – 2.07 respectively. The values of the band gap energy and refractive index obtained indicate possible applications in photovoltaic systems, optoelectronics, laser diodes and light emitting diodes.