Abstract
Polycrystalline copper sulphide (CuxS) thin films were grown by ultrasonic spray pyrolysis method using aqueous solutions of copper chloride and thiourea without any complexing agent at various substrate temperatures of 240, 280, and 320°C. The films were characterized for their structural, optical, and electrical properties by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX), atomic force microscopy (AFM), contact angle (CA), optical absorption, and current-voltage (I-V) measurements. The XRD analysis showed that the films had single or mixed phase polycrystalline nature with a hexagonal covellite and cubic digenite structure. The crystalline phase of the films changed depending on the substrate temperature. The optical band gaps (Eg) of thin films were 2.07 eV (CuS), 2.50 eV (Cu1.765S), and 2.28 eV (Cu1.765S–Cu2S). AFM results indicated that the films had spherical nanosized particles well adhered to the substrate. Contact angle measurements showed that the thin films had hydrophobic nature. Hall effect measurements of all the deposited CuxS thin films demonstrated them to be of p-type conductivity, and the current-voltage (I-V) dark curves exhibited linear variation.
Highlights
Copper sulphide (CuxS) has attracted a great deal of scientific attention due to the tunable semiconductive properties and approximate metallic behaviors depending on stoichiometry of the mineral phase [1]
The results indicate that crystallite size decreases as deposition temperature of the films increases
X-ray diffraction (XRD) pattern given in Figure 1 is evidence that TF1 thin film has CuS single phase, and the calculated energy band gap (Eg) using experimental data for TF1 thin film is in agreement with the Eg value reported by Grozdanov and Najdoski [34] and by Zhu et al [29]
Summary
Copper sulphide (CuxS) has attracted a great deal of scientific attention due to the tunable semiconductive properties and approximate metallic behaviors depending on stoichiometry of the mineral phase [1]. The ultrasonic spray pyrolysis technique is a simple coating technology in which an aqueous solution containing compounds in the form of soluble salts of each element is sprayed onto heated substrates. This process enables growth of nanostructured and high quality thin films and control of film thickness and stoichiometry. We try to explain crystalline phase transitions when the films are deposited at higher temperatures To our knowledge, such a detailed study on the effect of substrate temperature on the properties of copper sulphide thin films is still lacking
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