Electrical and Optical Properties of Gold-Strontium Titanate Nano-Composite Thin Films
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1129-V11-14
Electrical and Optical Properties of Gold-Strontium Titanate Nano-Composite Thin Films S. Ganti, Y. Dhopade, R.K. Gupta, K. Ghosh, P.K. Kahol Department of Physics, Astronomy, and Materials Science, Missouri State University, Springfield, MO 65897, U.S.A. ABSTRACT Thin films based on nano-composites have attracted considerable attention for their possible applications in devices and sensors. These nano-composite thin films are formed by embedding metal or semiconductor nano-particles in a host material and they exhibit interesting electrical transport properties. Using pulsed laser deposition technique, we have prepared nanocomposite thin films of gold-strontium titanate on quartz substrate. Gold and strontium titanate were used as targets for pulsed laser deposition. Thin films having different compositions were grown. The effect of different composition on their electrical and optical properties has been studied in details. The structural characterizations of the films were done by x-ray diffraction, transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. Transmission electron microscopy as well as atomic force microscopy shows the presence of gold nano-particles in these films. X-ray diffraction and energy dispersive x-ray spectroscopy shows the existence of strontium titanate and gold. Current-voltage characteristics and temperature dependent resistivity measurements were made to characterize electrical properties of these films. Electrical properties can be manipulated from metal to insulator through semiconductor by varying the composition. In addition, it is observed that the absorption of visible light increases with increase in gold percentage. This indicates that these nanocomposites could also use as active materials for many electronic as well as optical sensors. INTRODUCTION Pulsed laser deposition (PLD) technique is widely used for deposition of thin films of advanced materials having different properties [1]. The PLD has many advantages such as epitaxial growth of thin films [2], retention of target composition in the deposited films [3], and formation of multilayers [4]. To grow composite films by PLD, two approaches can be envisaged. The first is the combinatorial approaches, which is based on the use of multitarget systems. The second approach is to use the single target having the desired composition. In this paper, we report the properties of gold (Au)-strontium titanate (STO) nano-composites using combinatorial approach. STO is an insulator with a band gap of ~3.2 eV having perovskite crystal structure [5]. STO is widely used for ferroelectric applications because of its high dielectric constant [6]. The dielectric constant of STO is nearly 300 at room temperature and 10000 at low temperature. Rao et al have studied the effect of growth parameters such as ablation fluence, pressure, and substrate temperature on the properties of PLD grown STO films [7]. Several researchers have used STO as a dielectric in metal-oxide-semiconductor field effect tr
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