Nanocrystalline SnO 2 thin films were successfully prepared using Physical Vapour Deposition technique and were annealed at 400 o C. Structural, morphological, elemental, compositional, optical, and
IntroductionSince last few decades there has been an increasing interest to prepare inexpensive SnO 2 thin films. Tin oxide is the most widely used metal oxide semiconductor in gas sensing because of its capability to detect combustible and hazardous gases such as methane, LPG, CNG, CO, CO 2 , Cl 2 , H 2 S etc [1][2][3][4]. It is an n-type semiconductor of tetragonal structure with band gap energy about 3.6 eV at room temperature. It is cheap, nontoxic and has strong oxidizing power, high photochemical corrosive resistance, good electrical, optical and piezoelectric behavior. In recent years, semiconductor metal oxide films have received considerable attention because of their potential applications [5] such as photochemical and photoconductive devices in LCD, lithium-ion batteries,[6-8] a transport conductive electrode for solar cells [9,10] a gas sensing material for gas sensor devices [11], transport conducting electrodes [12] etc. The majority of the applications adopted SnO 2 as the sensing material due to its high sensitivity and stability at lower operational temperatures, in spite of its poor selectivity [13].Out of many thin film preparation techniques such as chemical vapour deposition [14], spray pyrolysis [15], sputtering [16], activated reactive evaporation [17], etc. Physical Vapour Deposition method is straight forward and simple one. Because of deposition in high vacuum and at room temperature, this technique produces contamination free uniform thin films. In the present study, we used Hind Hivac vacuum depositing unit for depositing pure tin onto the cleaned glass substrates at room temperature. The films were then heated in muffle furnace at 200 o C for 24 hrs to allow oxidation. The so formed pure SnO 2 thin films were then annealed at 300, 400 and 500 o C each for 2 hrs. Structural, morphological, electrical, optical and gas sensing characterizations of the samples were studied.
