Ž . Thin Solid Films 392 2001 226230 Surface textured ZnO films for thin film solar cell applications by expanding thermal plasma CVD R. Groenen a,  , J. Loffler b , P.M. Sommeling c , J.L. Linden d , E.A.G. Hamers a , ¨ R.E.I. Schropp b , M.C.M. van de Sanden a a Eindho en Uni  ersity of Technology, Department of Physics, P.O. Box 513, NL-5600 MB Eindho en, The Netherlands b Utrecht Uni  ersity, Debye Institute, Physics of De  ices, P.O. Box 80000, NL-3508 TA Utrecht, The Netherlands c ECN, Solar Energy, P.O. Box 1, NL-1755 ZG Petten, The Netherlands d TNO-TPD, Di  ision Materials Research and Technology, P.O. Box 595, NL-5600 AN Eindho  en, The Netherlands Abstract An expanding thermal plasma created by a cascaded arc is used to deposit surface textured ZnO films. Films have been Ž 3 . deposited at 150  350°C at a rate of typically 0.70 nms. They exhibit low resistivity 10  cm , high transmittance in the Ž . visible wavelength region 80% and a rough surface texture. The crystallite size and surface roughness increase with increasing deposition temperature and flow of argon ions. At the same time columnar textured growth gets less pronounced, a change to granular growth is observed. First p-i-n a-Si:H solar cells deposited on this material with initial efficiencies approaching 10% have been realised.  2001 Elsevier Science B.V. All rights reserved. Keywords: Zinc oxide; Plasma deposition; Surface texture; Solar cells 1. Introduction Ž . Zinc oxide ZnO is a promising transparent con- Ž . ducting oxide TCO for silicon based thin film solar cells. It exhibits superior transparency, stronger resis- tance to hydrogen plasma and requires lower deposi- tion temperatures as compared to the commonly used Ž . fluorine-doped tin oxide SnO :F which shows an ex- 2 cellent surface texture enabling effective light trapping   properties 1,2 . Textured ZnO films have been pre-   pared earlier by several deposition techniques 3  8. Surface texturing, however, generally requires a high deposition temperature, presence of water vapour in   the reaction mixture or post-deposition etching 3,6 8. In this paper a low temperature deposition technique for surface textured ZnO is presented utilising an ex- panding thermal plasma created by a cascaded arc. It  Corresponding author. Tel.: 31-40-265-0171; fax: 31-40-265- 0850. Ž . E-mail address: groenen@tpd.tno.nl R. Groenen . has been shown that this type of remote plasma is capable of producing high growth rates while the de-  sired material quality is maintained in a-Si:H 9 and   a-C:H 10 deposition. The surface texture, morphology, crystal orientation and film composition are studied. The first promising results on p-i-n a-Si:H thin film solar cells are high- lighted. The optical properties in relation to the ob- tained surface texture of ZnO films as well as compre- hensive results on first solar cells are presented in a   separate paper 11 . 2. Experimental Both undoped and aluminium doped ZnO films have Ž been deposited on Corning glass substrates 100  50 2 . mm using an Aixtron AIX 2300 MX pre-production reactor set up shown in Fig. 1. The plasma source is a low-flow cascaded arc consisting of three cathodes, a stack of water-cooled circular copper plates insulated from each other by boron nitride rings, an injection 0040-609001$ - see front matter  2001 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 0 4 0 - 6 0 9 0 01 01032-X