International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056 Volume: 03 Issue: 03 | Mar-2016 www.irjet.net p-ISSN: 2395-0072 © 2016, IRJET | Impact Factor value: 4.45 | ISO 9001:2008 Certified Journal | Page 40 Structural, Optical and Sensitive Properties of Ag-Doped Tin Oxide Thin Films Ahmad Z. Al-Janaby 1 , Hamid S. Al- Jumaili 1 1 Department of physics, College of Education for pure Science, University of Anbar, Al-Anbar, Iraq azidan652@yahoo.com, dr_hamid2020@yahoo.com ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - The present paper a SnO2 (Pure) and Ag doped thin films at different concentration (3, 5 and 7 vol.%) of Ag, were prepared by chemical spray pyrolysis. The films deposited onto glass slides were first cleaned with detergent water and then dipped in acetone and discusses the structural, optical and sensitive properties of Ag-doped tin oxide thin film prepared on glass substrate by the spray pyrolysis technique at a temperature of 400 ̊ C. X-ray diffraction study shows that the film was tetragonal rutile structure of SnO2. Morphology analysis studied by atomic force microscopy (AFM) and reveals that the grain size of the prepared thin film is approximately (73.41-111.62) nm, with a surface roughness of (2.18 – 2.79) nm as well as root mean square of ( 2.69 -3.39) nm for SnO2(pure)and Ag-doping, Optical characteristics were studied by UV/VIS Spectrophotometer at (300- 1100 nm) and observed that the transmission value was more than 75 % at the visible wavelength range. The direct energy gap (Eg) ranged between (2.73-3.22) eV, is measured by UV/VIS., and studied the sensor properties t0 NO2 gas with 3% ratio at a constant voltage of 6V, to found the optimum operation temperature at 150°C for all films, also the sensor work in room temperature. The sensitivity increases with temperature to arrive (81.6%) for SnO2: Ag films at 250°C. The response time was (5.4sec) and the recovery time was (27sec) for SnO2: Ag gas sensor. The results obtained that SnO2 film prepared by chemical spray pyrolysis pure and doped by Ag were a good sensitive for NO2 gas. Key Words: Structural, Optical and Sensitive Properties, Thin Film, SnO2: Ag. 1.INTRODUCTION The study and application of thin film technology is entirely entered in to almost all the branches of science and technology. Present study which describes the synthesis and study of structural, optical and sensitive characteristics of Ag doped tin oxide (SnO2) is really more interesting for researchers due to its vast applications. Due to the properties like reflectivity, transparency, low electrical sheet resistance etc., tin oxide thin films has immense applications such as gas sensing material for photovoltaic cell in transistors, transparent conductive electrode for solar cells photochemical and photoconductive devices in liquid crystal display [1] gas sensor devices [2,3]. Till to day so many methods were adopted to synthesize doped or un-doped tin oxide films such as R.F. Magnetron Co- sputtering, Thermal Evaporation, and Chemical Vapor Deposition, Laser Pulse Evaporation, Sol-Gel, Spray Pyrolysis and ultrasonic spray pyrolysis [4, 5, and 6]. Tin oxide crystallizes tetragonal rutile structure [7, 8] with unit cell parameters a=b= 4.737A and c= 3.186 A. It is an n-type semiconductor having high band gap energy ȋ≈ ͵.͸ eVȌ [9, ͳͲ] with high chemical and mechanical stabilities [11] and is more transparent in the region of visible spectrum due to high band gap, having high electrical conductivity due to free electrons in oxygen vacancy holes [ 12, 13]. 2. EXPERIMENTAL A SnO2 (Pure) and Ag doped thin films at different concentration (3, 5 and 7 vol.%) of Ag, were prepared by chemical spray pyrolysis. The films deposited onto glass slides were first cleaned with detergent water and then dipped in acetone. Spray solution was prepared by mixing 0.1 M aqueous solutions of SnO2, and AgNO3 at ratio (3 ,5 and 7 vol.%) using a magnetic stirrer. The automated spray solution was then transferred to the hot substrate kept at the normalized deposition temperature of (400°C) using filtered air as carrier gas at a flow rate normalized to approximately (3) ml/min. To prevent the substrate from excessively cooling, the prepared solution was sprayed on the substrate for 10 s with 15 s intervals. The films had a uniform thickness of range (400) nm. The structural properties were determined by X-ray diffraction ȋXRD; ShimadzuȌ with CuKȽ radiation ȋλ= Ͳ.ͳͷͶͲ͸ nmȌ. Film morphology was analyzed by atomic force microscope (AFM)-type (CSPM). The optical absorption and transmission spectra were obtained using a UV-VIS spectrophotometer 6800JENWAY, Germany) within the wavelength range of (300-1100) nm. For measuring this parameter ȋsensitivity, response time, …. etc.Ȍ We depend upon the difference of resistance or the current through films when the surface of thin films dispose to (NO2) at certain temperature for measuring the sensitivity of films and knowing the temperature through or by thermocouple of heater. we used the system to know the sensitivity for different gases and they are from the following parts .1- Vacuum pumping (Rotary). 2-Connecting pipes. 3- Measurement for vacuum. 4- Chamber cylindrical stainless steel, diameter 30cm and 35cm high, and the chamber contain the following, A- Let for testing gas. B- valve for entering the air after vacuum. C- Glass window. At the