Electrical Effect of Zinc Nano-Particles on CdS Films Grown by Slow Solution Process
Journal of Scientific and Engineering Research, Vol. 4(5), p. 253-260, 2017
8 Pages Posted: 24 Jul 2017
Date Written: July 20, 2017
In reality, the electric charges that may appear due to certain specific adsorption of the amphoteric hydroxyl group from the complexing agent is assumed to lead to superficial negative charges in the alkaline media of the chemical bath solution and hence positive charges in the acidic chemical bath media. Since the desolating agent is de-ionized water, the nano-particles become charged particles that are peptizable in de-ionized water. But this is only possible with low polarizing counter-ions. When zinc, cadmium and sulphur soluble compound are used, Zn+2 and Cd+2 with S+2 particles formed after coprecipitation in alkaline solution cannot be directly solubilized in water-based growth media. The presence of "the primary" too polarizing counter-ions such as (CH3)NH3+ or NH4+ from the complexing agent that remains after the reaction forms a screening effect on charged particles. This consequently reduces charge repulsion between particles and this increases particles aggregate forming doped thin films whose electrical properties are modified as per the level of doping concentration. This research paper investigated the effect of Zinc nanoparticles on cadmium sulphide thin film‟s electrical properties as a function their as-deposited thicknesses. Solution technique was used to grow thin films on ordinary microscope substrate slides from aqueous solutions of Zn+2 and Cd+2 with S+2 ions in the presence of TEA. By varying its deposition time only to obtain eleven (11) samples, resistance was measured using a two point probe while its conductivity type was measured using a Gauss meter as a function of their thicknesses. The thin films were found to be n-type semiconductors with a very high valence electron density, a band gap of 2.43 eV, an average transmittance above 79% on in the VIS - NIR region and a resistivity of 9.5×101 – 1.22×102 Ω-cm. Sheet resistivity increased with an increase in Zn ion concentration.
Keywords: Nano-Particles, Solution Technique, Band Gap, Counter-Ions, Complexing Agent, Semiconductor
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