Abstract
Transition metal chalcogenide nanocomposite thin films deposited by chemical routes are currently attracting wide attention being inexpensive, simple and have utility for large area applications. The role of substrate becomes very important in film deposition as well as in controlling their properties due to strain induced properties modification and lattice mismatch. CuS/PVA nanocomposite thin films were successfully deposited on glass and silicon substrates using sol-gel technique. Thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), UV-visible (UV-VIS) and Raman spectroscopy. Structural data confirm the amorphous nature of as grown films which transform into crystalline films after annealing at 200°C. The degree of crystallinity seems to be better in film deposited on silicon substrate in comparison to those grown over glass substrate with average crystallite sizes ≅ 4.00 nm and 7.00 nm for films deposited on glass and silicon substrate respectively. Atomic force microscopy (AFM) images in dynamic as well as contact modes display nanoparticles embedded in polymer network. The films surface roughness parameters quantitatively estimated from AFM micrographs are compared. Raman spectra show a sharp peak at ≅474 cm¯1 assigned to S-S stretching mode of S2 ions in films grown on both substrates and associated as due to presence of hexagonal (covellite) crystal structure. Optical band gaps of thin film on glass and silicon substrate are 2.10 eV and 2.02 eV respectively. The effect of substrate on the measured properties is discussed.
Highlights
Copper sulfide belonging to IB-VIA group is an important and attractive material due to the wide range of applications in optical and electrical devices, and due to relatively non-toxic nature [1] [2] [3]
Thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), UV-visible (UV-VIS) and Raman spectroscopy
XRD patterns of as deposited thin films of CuS/PVA nanocomposite on both glass and silicon substrates do not show any XRD peak corresponding to CuS indicating that as grown films are amorphous in nature
Summary
Copper sulfide belonging to IB-VIA group is an important and attractive material due to the wide range of applications in optical and electrical devices, and due to relatively non-toxic nature [1] [2] [3]. Various factors influence the physico-chemical properties of nanocomposite including the particle separation, the inter-phase interaction, the nature of polymer matrix and the substrate used for growing the nanocomposite thin film, etc. It has been shown that the electrical, optical and structural properties of chalcogenide nanoparticles get affected when embedded in polymeric matrix; the nanocomposite based on pure phase CuS with polymers are sporadic only. PVA hydrogel is most promising polymers due to its unique properties such as high transmittance, easy processability, noncorrosive nature and good thermal stability over a wide range of temperature, making it an ideal matrix for optoelectronic applications [12] [13]. CuS/PVA nanocomposite thin films deposition on glass and silicon substrate has not been reported to the best of our knowledge. The effect of substrate on structural, micro-structural, surface roughness and optical band gap are investigated and discussed
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