Effect of the hydrogen bonding and content on the opto-electronic properties of radiofrequency magnetron sputtered hydrogenated amorphous silicon ®lms M.Daouahi a ,A.BenOthmane b ,K.Zellama c, * ,A.Zeinert c ,M.Essamet b ,H.Bouchriha b a Faculte  des Sciences de Bizerte, 7021 Zarzouna, Bizerte, Tunisia b Faculte  des Sciences de Tunis, Campus Universitaire Elmenzeh, 1060 Tunis, Tunisia c Laboratoire de Physique de la Matie Áre Condense Âe, Faculte  des Sciences d'Amiens, 33 Rue Saint-Leu 80039 Amiens Cedex, France Received 5 May 2001; accepted 16 May 2001 by J.F. Sadoc Abstract Infrared absorption and optical transmission combined with photothermal de¯ection spectroscopy experiments have been used to study the effect of the hydrogen bonding and content on the opto-electronic properties of hydrogenated amorphous silicon a-Si:H) ®lms prepared by radiofrequency magnetron sputtering at high deposition rates 11±15 A Ê /s), at the same substrate temperature 2508C) and with different H 2 dilution percentage. The results indicate that the electronic properties, in terms of density of defects and disorder, are dependent on both the relative proportion of the isolated monohydride Si±H bonds and the presence in the ®lms of structural inhomogeneities, while the optical gap is found to be rather controlled by the totalbondedhydrogencontentC H .Optimized®lmswithquitelowdensityofdefectsanddisorderandwhichcontainthehighest proportion ,38%) of isolated monohydride complexes are obtained. An increase in the proportion of the polyhydride and/or theclusteredmonohydridecon®gurationsgivesrisetomoregasstatesanddisorderandfavorstheformationofhigherstructural inhomogeneities such as voids. q 2001 Elsevier Science Ltd. All rights reserved. PACS: 78.30.Ly; 61.43.Dq; 71.23.Cq; 81.05.Gc Keywords: A. Disordered systems; A. Semiconductors; D. Optical properties; D. Electronic states localized) 1. Introduction Thehydrogenincorporatedduringgrowthofa-Si:H®lms, not only saturates the silicon dangling bonds leading to a decrease in the mid-gap density of defects, but also reduces the structural disorder which results in the narrowing in the bandtailstates[1,2].Asaresult,agreatimprovementofthe opto-electronic properties of the ®lms is observed [3]. It has been also shown that, depending on the deposition conditions, different silicon±hydrogen bond con®gurations can be incorporated and strongly in¯uence the physical properties of the ®lms [3±6]. The optimization of these conditions is therefore of crucial importance for the fabri- cation of device quality material [7]. Several studies have been conducted on a-Si:H ®lms essentially deposited by radiofrequency rf) plasma enhanced chemical vapor deposition PECVD), using pure or diluted silane gas [8±10], or by dc and simple cathode sputtering method using crystalline silicon target [11±13], and only few studies have been devoted to the rf magnetron sputteringtechnique[14±16].Theadvantageofthismethod is that by varying the hydrogen proportion in the gas phase mixture Ar 1 H 2 ; one can vary in a large range and inde- pendently from the rf power, the hydrogen content in the ®lms. Furthermore, the use of the magnetron component allows a con®nement of the plasma at the silicon target and therefore increases the ionization process. Combined with the rf power, one can reach deposition rates signi®- cantly higher up to 20 A Ê /s) than those obtained with the conventionalPECVDmethod.Theseargumentssuggestthat Solid State Communications 120 2001) 243±248 0038-1098/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved. PII:S0038-109801)00350-7 PERGAMON www.elsevier.com/locate/ssc * Corresponding author. Tel.: 133-3-22-82-75-97; fax: 133-3- 22-82-78-91. E-mail address: kacem.zellama@sc.u-picardie.fr K. Zellama).