Formation Of CuAIO2 Thin Films By Ultrasonic Spray Pyrolysis For Photodiode Applications

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Date
2011-08
Authors
Suhariadi, Iping
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Publisher
Universiti Sains Malaysia
Abstract
CuAlO2 is a p-type oxide which is transparent. When coupled with an n-type material, a p-n junction can be created and can be used in many interesting optical and electronic applications. Smooth, crack free and homogenous CuAlO2 film was produced by chemical solution deposition process via ultrasonic spray pyrolysis (USP) technique on a cleaned n-type Si substrate. The precursor solution used was comprised of a mixture of Cu(NO3)2.3H2O and Al(NO3)3.9H2O. The deposition parameter influences the film properties are the flow rate of carrier gas, nozzle-substrate distance, substrate‘s temperature and Cu to Al ratio was studied thoroughly. The optimum parameters were found for the films deposited at a flow rate of 1 L/min, nozzle-substrate distance of 3 cm, substrate‘s temperature of 550°C and Cu to Al ratio of 1.2:1. The flow was seen to be laminar at this distance and flow rate of carrier gas. The formation of films was proposed to be due to the pyrolytic reaction of Cu and Al ions in the droplets when the droplets impinged on the heated substrate. SEM images of the most optimum sample is consisted of uniform grains with film thickness of ~1.9 μm. UV-Vis spectroscopy revealed that the film have energy gap of 3.54 eV with transparency above 60 % at visible light range. The conductivity of the film was 0.354 Scm-1. The film showed the rectifying nature of diode in a junction of p-type CuAlO2/n-type Si with turn on voltage around 0.4 eV. Under various illumination of incandescent lamp, the diode showed photoelectric effect.
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Keywords
Formation of CuAlO2 thin films , ultrasonic spray pyrolysis
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