**3. Results and discussion**

78 Solar Cells – Thin-Film Technologies

an argon atmosphere, which has almost the same thermal expansion coefficient of 4.5×10-6K-1 as that of the silicon film (Linke et al., 2004; Goesmann et al., 1995). This tungsten interlayer was used as a thermal and mechanical supporting layer for deposition of the silicon film. Nanocrystalline silicon films were then deposited on the tungsten interlayer by the plasma enhanced chemical vapour deposition process (PECVD) within SiHCl3 and H2 atmosphere. Details of the process were described in References (Rostalsky et al., 2001; Gromball et al., 2004, 2005). The power density used was 2.5W/cm2. The gap in the PECVD parallel plate reactor was 10mm and the substrate temperature was 550℃. The flow rate H2/SiHCl3 is 0.25 to reduce the hydrogen and chlorine content in the film. Boron trichloride (BCl3) was added in the gas for an in-situ p-doping. The process pressure was chosen to 350 Pa for the minimized stress. At the above conditions, the deposition rate up to 200nm/min was obtained. After a silicon film of 15-20μm thickness was deposited, a SiO2 layer of 400nm thickness was deposited on the top of the silicon from SiHCl3 and N2O within 5 min to

Fig. 2. Schematic of the linear electron beam recrystallization system (Gromball et al., 2005)

prevent balling up.

Fig. 1. Structure of thin film silicon solar cell
