Thickness and Composition of F-doped SnO 2 Thin Films as Determined by Rutherford Backscattering Spectrometry Teerasak Kamwanna 1 , Suparerk Aukkaravittayapun 2 , Somsorn Singkarat 1 , and Thiraphat Vilaithong 1 1 Fast Neutron Research Facility (FNRF), Faculty of Science, Chiang Mai University, Chiang Mai 50200 Phone 0-5394-2464, Fax.0-5322-2776 E-mail: kamwanna@yahoo.com 2 National Metal and Materials Technology Center, 114 Thailand Science Park, Paholyothin Rd. Klong 1, Klong Luang, Pathumthani 12120 Phone 0-2564-6500, Fax. 0-2564-6447, E-mail: suparerk@mtec.or.th Abstract F-doped SnO 2 films were fabricated on silicon wafers by inverted pyrosol technique. The films were characterized by Rutherford backscattering spectrometry (RBS) and scanning electron microscopy (SEM) in order to determine film thickness and composition. RBS technique revealed that O/Sn ratio of the films was around 2.03-2.18. 1. Introduction Tin oxide (SnO 2 ) is an important oxide used as an efficient dielectric material, catalytic material, sensing material and transparent conducting material. Doped SnO 2 films are used as transparent conductors in liquid crystal displays, thin-film solar cells and other optoelectric device applications [1]. Fluorine is a preferred dopant because it can provide high transparency and conductivity [2]. Ion beam analysis (IBA) techniques are the methods of choice to determine the thickness and the composition of thin films at near-surface region, i.e. to depths of ~ 0.5 μm [3]. Among these, Rutherford backscattering spectrometry (RBS) is the most commonly used on account of its several advantages such as a non- destructive , simple and fast method with a quantitative analysis capability. In this work we have investigated the thickness and composition of thin SnO 2 films deposited on silicon substrates. 2. Experimental F-doped SnO 2 films with different F/Sn molar ratio in precursor solution were deposited on (001) silicon wafers by an inverted pyrosol technique [4]. The solution was a mixture of SnCl 2 .2H 2 O in a solvent, containing 5% DI water and 95% ethanol with different amount of NH 4 F (F/Sn = 0.00, 0.06, 0.09, 0.12, 0.75 and 2.5) as a fluorine dopant agent. The substrate temperature was set at 450 o C. The thickness and the composition of the thin SnO 2 films were investigated by RBS technique and scanning electron microscopy (SEM). A collimated 2.13 MeV 4 He 2+ ion beam with a diameter of 1 mm and with a divergence of less than 0.05°, from 1.7-MV tandem accelerator, was used for the RBS analysis. The backscattered beam was detected at scattering angle of 170° by a standard SSB detector. A schematic representation of RBS measurement system at Chiang Mai University was drawn in Figure 1. The sample holder was electrically isolated from the RBS chamber and acts as a Faraday cup. During measurement the RBS chamber was under a vacuum pressure of 5 x 10 -6 mbar. The thickness and the composition of SnO 2 films were calculated by way of making a comparison between the collected spectra and the simulated spectra from SIMNRA code [5]. Direct result of thickness from the code is normally expressed in the unit of atoms per unit area. The conversion into the unit of length was executed C18