THERMAL OXIDATION AND ANNEALING EFFECT ON TIO 2 FILMS PROPERTIES FOR SOLAR CELL K. P. Lim 1 , K. Ibrahim 2 , I. M. Hamammu 3 School of Physics, Universiti Sains Malaysia, 11800 Minden, Penang, MALAYSIA. Tel.: +6-012-4575597, fax: +6-04-657-9150 1 estherlimk@yohoo.com , 2 kamarul@usm.my 3 Faculty of Science, Garyounis University, P.O.Box 9480, Benghazi, Libya ABSTRACT Titanium dioxide (TiO 2 ) thin films were yielded by thermal oxidation and annealing process of Titanium (Ti) films as-deposited using the DC magnetron sputtering technique at different temperature. P-type silicon with (111) orientation was used as substrate. The structure and composition of the TiO 2 thin films were analyzed using energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). The optical properties of the films were characterized by spectral-reflectance measurement and MATLAB assisted variable-angle ellipsometer. Rutile structure was obtained for with TiO 2 thin films on SiO 2 interlayer by oxidation and annealing at 773 K. This SiO 2 passivation layer improved the open circuit voltage for an acidic nanotextured silicon solar cell. A high transmission, low reflection and approximately zeros absorption at wavelength of 632.8nm films were obtained. The films also possessed an index of refraction of 2.65. Therefore our work has reasonably shown an effective way of developing ARC films for solar cells. INTRODUCTION As we know the fossil fuel reserve is finite and crude oil price threatened by shortage of supply recently has affected the global economy. One of the ways to wean ourselves from fossil fuel is to use renewable energy. Photovoltaic solar cell is one of the renewable energy technologies which convert incoming solar radiation directly into electricity. One of the critical design aspects to develop efficient solar cells is optimization of light absorption by methods like antireflection coatings (ARC), as well as techniques that force the light to travel long pathways within the fabricated solar cell device (Green, 2004; Zhao, 2004). Titanium dioxide (TiO 2 ) is one of the materials which are economical and possess excellent optical properties to be used as ARC. TiO 2 single layer has been found to exhibit a minimum reflectance at wavelength of about 600nm (Green, 1995). Solar spectrum at air mass (AM) 1.5 has wavelength in the range of 500-700nm and yields a total irradiance of 1000W/m 2 (Smestad, 2002). The aim of this work is to evaluate the performance of TiO 2 fabricated using non-conventional method as ARC in solar cells. Attempts to relate the effect of post deposition oxidation and post oxidation annealing on the composition, structural and optical properties of TiO 2 films were made in this study. Furthermore the developed films were used as an antireflection coating for acidic nanotextured silicon solar cells. The current-voltage characteristics of the silicon solar cells before and after applying TiO 2 were used to study the efficiency of the films as ARC. EXPERIMENTAL Titanium (Ti) thin film was deposited on to a substrate using a DC magnetron sputtering system Edwards 306 at room temperature. P-type silicon with (111) orientation was used as substrate. The substrate was cleaned using RCA technique prior to the metal deposition. A Ti plate of 5cm in diameter was used as sputter target. Sputtering was carried out in an atmosphere of high purity argon (99.999%) and other relevant conditions are listed in the Table 1. Before actual deposition, the target was pre-sputtered in argon atmosphere for 1-2 min in order to remove the surface oxide layer of the target. Deposition was carried out at a plasma pressure of 5.5x10 -3 torr. The deposited Ti films were thermally oxidized at 773 K and 873 K in oxygen ambient in a quartz tube furnace. The oxidized films were subsequently annealed at 673 K, 773 K and 873 K temperature in nitrogen ambient.