Electrical and structural properties of nano-crystalline silicon intrinsic layers for nano-crystalline silicon solar cells prepared by very high frequency plasma chemical vapor deposition

Thin silicon intrinsic layers were deposited in the amorphous to nano-crystalline transition regime to investigate their structural and optoelectrical properties using the very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) technique. Optical emission spectroscopy (OES) was primarily used to monitor the plasma properties during the deposition. The ratio Hα/Si*Hα/Si*, estimated from OES spectra, is closely related to the microstructure of the films. With the increasing plasma power from 10 to 50 W, the ratio Hα/Si*Hα/Si* increases leading to nano-crystalline films. The ratio Hα/Si*Hα/Si* decreases with the increase of process gas pressure at constant power of 15 and 30 W. The films were nano-crystalline at low pressure and became amorphous at high pressure.