Effect of the precursor solution concentration on the NiO thin film properties deposited by spray pyrolysis

摘要

NiO thin films have been deposited by chemical spray pyrolysis from nickel chloride hexahydrate (NiCl(2)(.)6H(2)O) solution in water. The substrate temperature during deposition is around 350 degrees C. The solution flow rate was 10 ml/min. The nickel chloride concentration in the solvent has been used as parameter. It varies from 0.05 to 0.5 M. It is shown that the NiO film properties depend strongly on the nickel chloride concentration. Below 0.3 M, the final thickness of a film deposited using 50 ml of solution is around 0.5 pm. From 0.3 to 0.5 M the thickness is around 3 pm. There is a threshold value for the different film properties when the precursor concentration varies between C = 0.2 and 0.3 M. The oxygen concentration present in the films decreases from 1. in the case of small molar concentration, to 0.86 for 0.3 M and more. In the X-ray diffraction diagram, the more intense contribution is systematically the (1 1 1) peak, while the (2 0 0) diffraction peak is small. This last peak increases slowly up to 0.3 M with the NiCl2 concentration, and then it stabilizes. Also, the conductivity decreases when the molar concentration of NiCl2 increases, to stabilize at around 0.3 M. Moreover, while, as expected, the films are p-type when the molar concentration is smaller than 0.3 M, they becomes n-type for higher concentrations.