Thin Solid Films 430 (2003) 157–160 0040-6090/03/$ - see front matter  2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0040-6090(03)00095-6 Substrate influence on the properties of doped thin silicon layers grown by Cat-CVD D. Soler *, M. Fonrodona , C. Voz , J.M. Asensi , J. Bertomeu , J. Andreu a, a b a a a Departament Fısica Aplicada i Optica, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona, Spain a ` ´ Departament Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita syn, Modul C4, 08034 Barcelona, Spain b ` ` ` ` Abstract We present structural and electrical properties for p- and n-type layers grown close to the transition between a-Si:H and nc- Si:H onto different substrates: Corning 1737 glass, ZnO:Al-coated glass and stainless steel. Structural properties were observed to depend on the substrate properties for samples grown under the same deposition conditions. Different behaviour was observed for n- and p-type material. Stainless steel seemed to enhance crystallinity when dealing with n-type layers, whereas an increased crystalline fraction was obtained on glass for p-type samples. Electrical conduction in the direction perpendicular to the substrate seemed to be mainly determined by the interfaces or by the existence of an amorphous incubation layer that might determine the electrical behaviour. In the direction perpendicular to the substrate, n-type layers exhibited a lower resistance value than p-type ones, showing better contact properties between the layer and the substrate.  2003 Elsevier Science B.V. All rights reserved. Keywords: Catalytic chemical vapour deposition; Nanocrystalline silicon; Amorphous silicon; Doping 1. Introduction Silicon thin films obtained close to the transition between nanocrystalline silicon (nc-Si:H) and amor- phous silicon (a-Si:H) growth have recently been proved as especially suitable when applied to solar cells obtained by catalytic chemical vapour deposition (Cat- CVD), also called hot-wire CVD (HWCVD) w1x. The microstructure of silicon thin films prepared by Cat- CVD can be considerably influenced by slight changes in the deposition parameters. In particular, the transition from a-Si:H to nc-Si:H can be observed in a narrow range of hydrogen dilution (D ) w2,3x. Furthermore, the H above-mentioned transition has also been proved to depend on the properties of the substrate on which the sample is grown for both plasma-enhanced CVD (PE- CVD) and Cat-CVD w4,5x. Different solar cell configurations (p–i–nyn–i–p) require controlled growth of both p- and n-type layers on different substrates. p–i–n cells are usually deposited onto transparent conductive oxide (TCO), whereas n– i–p cells are commonly grown on metallic substrates. *Corresponding author. Tel.: q34-93-4021134;fax: q34-93- 4021138. E-mail address: dsoler@fao.eb.es (D. Soler). Thus, the substrate influence on the microstructure and electrical properties of the doped layers has to be carefully considered, especially when dealing with dep- osition conditions close to the transition zone. Moreover, p- and n-type layers used in solar cells are typically very thin, so the initial stages of growth may have a very important influence on the final properties of the layer. In this study we focus on the low-temperature depo- sition of doped layers in the region of 100 nm close to the transition zone by Cat-CVD on different substrates. We show that p- and n-type films exhibit different behaviour regarding microstructural and electrical properties. 2. Experimental Doped thin silicon layers with thickness in the region of 100 nm were simultaneously deposited onto Corning 1737 glass, stainless steel (SS) and ZnO:Al-coated glass in a Cat-CVD set-up described elsewhere w6x. Dissoci- ation of the gases was achieved by means of a tantalum filament resistively heated up to a temperature of approximately 1800 8C. A process pressure of 3=10 y2 mbar was used, while a substrate temperature of 200 8C