Characterization of hydrogenated amorphous silicon thin films prepared by magnetron sputtering Maruf Hossain * , Husam H. Abu-Safe, Hameed Naseem, William D. Brown Arkansas Advanced Photovoltaic Research Center, Department of Electrical Engineering, 3217 Bell Engineering Center, University of Arkansas, Fayetteville, AR 72701, United States Received 4 September 2005; received in revised form 10 November 2005 Abstract Magnetron sputtered hydrogenated amorphous silicon (a-Si:H) thin films have been characterized. Hydrogen (H 2 ) with argon (Ar) was introduced into the sputtering chamber to create the plasma. A sudden increase in the deposition rate occurred when the hydrogen was added. The maximum hydrogen content of 16 atomic percent (at.%) was achieved and a bandgap of about 2.07 eV was determined from the spectral investigations of the hydrogenated films. The effect of radio frequency (RF) power on the deposition rate, as well as on the hydrogen content was investigated. To change the hydrogen content in the films, the hydrogen flow rate was varied while keeping the argon flow rate constant. The hydrogen content in the films increased with increasing hydrogen flow rate up to the maximum content of 16 at.% and then decreased for further increases in hydrogen flow. Ó 2005 Elsevier B.V. All rights reserved. PACS: 71.23.Cq; 78.66.Jg; 81.05.Gc; 81.15.Cd Keywords: Sputtering; Silicon; Photovoltaics; X-ray diffraction; FTIR measurements 1. Introduction Hydrogen plays an important role in determining the electrical properties of a-Si:H. Most high quality a-Si:H films are prepared by plasma-enhanced chemical vapor deposition (PECVD) [1] and the resulting films contain a fixed amount of hydrogen for a given deposition tempera- ture. Thus, the only way to vary the hydrogen content in PECVD a-Si:H films is by varying the deposition tempera- ture. For sputter-deposited films, hydrogen must be incor- porated into the film by introducing hydrogen into the sputtering chamber. The amount of hydrogen introduced into such films is controlled by the hydrogen flow provided during the sputtering process. Many researchers have studied the effect of hydrogen on the deposition rate of sputter-deposited a-Si:H. Savvides [2] reported the variation of deposition rate with hydrogen partial pressure for films prepared by dc planar magnetron reactive sputtering. In their experiments, argon partial pressure and magnetron discharge current were held con- stant and the hydrogen partial pressure was varied. The deposition rate decreased slightly for small amounts of hydrogen, but then remained constant for further increases in hydrogen partial pressure. When they kept hydrogen partial pressure constant and observe the discharge current as a function of hydrogen, they found that the discharge current increased with the addition of hydrogen, and, at high discharge currents, the deposition rate increased. Saito et al. [3] prepared hydrogenated films using RF planar magnetron sputtering. They deposited films using hydro- gen mixed with four different inert gases, helium (He), neon (Ne), argon (Ar) and krypton (Kr). The deposition rate was determined as a function of hydrogen partial pressure. Their results show that deposition rate decreases as the hydrogen partial pressure increases when mixed with He, 0022-3093/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2005.11.023 * Corresponding author. Tel.: +1 479 283 3226. E-mail address: maruf72703@yahoo.com (M. Hossain). www.elsevier.com/locate/jnoncrysol Journal of Non-Crystalline Solids 352 (2006) 18–23