novel method for fabrication of nano-crystalline silicon films is reported by using consecutive plasma hydrogenation and annealing steps. Formation of nano-size grains is achieved through hydrogenation of deposited amorphous silicon layers with no need to ion implantation or wet chemical processing. Amorphous silicon films are deposited on an oxide-coated (100) n-type silicon substrate. Nano-size crystallization is achieved using plasma-assisted hydrogenation using a PECVD reactor. This hydrogenation step is followed by an in-situ annealing step inside the reactor and the process is repeated for three times. We believe in the process of hydrogenation, hydrogen radicals attach to Si dangling bonds and during the de-passivation step, they impart energy to silicon atoms, enhancing the chance for nucleation and growth of nano-crystalline sites. The samples are characterized by SEM, TEM and photoluminescence (PL) analyses. Small isolated grains smaller than 50nm are observed. The peak of the PL spectrum varies between 550nm and 650nm for different conditions in experiments. All the analyses show that by decreasing the grain size the peak shifts toward smaller wavelengths with a lower peak intensity. Preliminary images were obtained using patterned structures on nano-crystalline silicon samples, indicating the efficacy of this technique for integration in standard silicon technology.

 SEM images of nanostructures of silicon under different condition: (a) and (b) plasma power (6.5w/cm²), different temperatures of 350º C and 400º C respectively. (c) Si sample annealed at a reduced power of 4.5w/cm².  By reducing the plasma power and increasing the annealing temperature smaller grains are achieved.

 TEM analyses for the silicon films, bright field and dark field images, indicating grains between 3 and 10 nm.

SEM imaging of P-Si nanostructure, light emission of  the patterned P-Si

 Selected area diffraction pattern of nano-crystalline Si

photoluminescence analysis of P-Si 

 PL measurement on various samples prepared using this study, (a) films with larger grains and less spread in grain distributions

(b) films with smaller grains and more distribution of the grain sizes. By raising the plasma power, smaller grains are resulted.

The Pl analysis of Nano- crystalline of silicon that indicated the red and green wavelength from band gap