Open Journal of Physical Chemistry, 2012, 2, 103-106 http://dx.doi.org/10.4236/ojpc.2012.22014 Published Online May 2012 (http://www.SciRP.org/journal/ojpc) 103 Effect of Annealing Temperature on the Optical Properties of Palladium Thin Film Feridoun Samavat * , Farzane Mahmoodi, Parisa Taravati Ahmad, Mohammad Faraz Samavat, Mohammad Hossein Tavakoli, Sanaz Hadidchi Department of Physics, Bu-Ali Sina University, Hamedan, Iran Email: * Fsamavat@yahoo.com Received February 13, 2012; revised March 25, 2012; accepted April 26, 2012 ABSTRACT In this paper, the effect of annealing temperature on the optical properties of palladium thin films has been investigated. The Pd thin films with thickness of about 123 Å were deposited on glass substrates by electron beam coating method. Then the palladium thin films were annealed in air at 350˚C, 450˚C, 550˚C and 650˚C for 1 h and then cold slowly. All the initial Pd films were found to have amorphous structure. Their optical properties were studied as function of an- nealing temperature using Ultraviolet-Visible (UV-Vis) spectroscopy. The direct band gaps in Pd films have been de- termined. Decreasing the values of the direct band gap shows also increasing the Pd crystallite nanostructure with in- creasing annealing temperature. Keywords: Pd Properties; Coating; XRD; Band Gap; Annealing; Crystallite Nanostructure 1. Introduction The structure and microstructure of systems containing nanoparticles have recently been extensively investigated. This is due to a rich number of fascinating properties ob- served in materials containing small submicrometer clus- ters, which imply promising applications in various areas of nanotechnology [1]. Thin films of metal nanoparticles have been receiving increasing attention because of the optical, electronic, and catalytic properties of such materi- als [2]. Thin films palladium have been the focus of many studies because of their ability to separate hydrogen from other gases [3]. Furthermore Pd has remained a focus of the material science community due to its important band gap, conversion efficiency, high absorption coefficient, stability and there exists a vast literature covering theo- retical and experimental studies of electronic band struc- ture [4-6]. Pd has a wide and direct band gap, n-type semiconducting material and found in crystalline form fcc phase [2]. A number of deposition techniques are being used for the fabrication of Pd thin films including thermal evaporation, chemical bath deposition, vacuum evaporation, chemical vapour deposition, spray pyrolysis, metal or- ganic vapour-phase epitaxy, closed space sublimation, pho- tochemical deposition, radio frequency sputtering, vapour transport deposition electro deposition, screen printing , pulsed laser deposition and couting [7]. 2. Experimental In this research program, palladium metal (99/95% pure) was purchased from goodfellow Co. Thin films of palla- dium were prepared by electron beam coating method on glass substrates using graphite crucible. Substrates were cleaned for about 5 min by ultrasonic cleaner. The sys- tem was pumped to a base pressure of less than 3 × 10 –5 mbar before deposition. Other coating parameter were cathode voltage 8.5 kV, substrate temperature 32˚C, coat- ing rate 12 Å·s –1 . Film thickness was estimate to be about 123 Å. These films were then annealed in air at various temperatures ranging from 350˚C to 650˚C for a fixed time of 1 h. The structure of these films was studied by X-ray dif- fraction (XRD) using Cu Kα (1.5418 Å) radiation with operating voltage/current of 40 kV. The optical property including optical band gap were calculated from the trans- mission spectra between 300 - 900 nm recorded by UV- Vis spectrometer. In this research, Pd thin films have been coated by elec- tron beam coating and their properties surveyed by UV- Vis spectrometer. 3. Results and Discussion 3.1. Structure Analysis The structures of the Pd thin films were studied using X-ray diffraction (XRD) technique. The diffraction spec- * Corresponding author. Copyright © 2012 SciRes. OJPC