Spectral and Morphological Studies of Nanocrystalline Silicon Thin Films Synthesized by PECVD for Solar Cells

Abstract

In this work, a series of nanocrystalline silicon films were studied with different microstructural tools to elucidate the film microstructure at different stages of growth. Thin Si films, with a series of multilayers, were deposited by radio frequency glow discharge using Plasma Enhanced Chemical Vapour Deposition (PECVD) in silane gas (SiH 4 ) highly diluted by hydrogen. Different nanostructured films were prepared by systematically varying gas flow ratios (R=1/1, 1/5, 1/7.5, 1/10, 1/15, 1/20) for films having different thicknesses. By changing the structure of the material, going from pure amorphous to nanocrystalline silicon, it is possible to obtain a variation in optical gap using the same material. In these structures, layers with different individual optical gaps are stacked together in order to cover as much of the solar spectrum as possible. The nanostructures of the silicon thin films were studied using FTIR, RS, PL, XRD, AFM, SEM, TEM and HRTEM. The results were correlated for conglomerate surface, grain surface. Some theoretical calculations were used for designing the overall stack geometry and for interpretation of characterization. These agree well with experimental observation.

Optical and Structural Properties of Silicon Nanocrystals Embedded in SiOx Matrix Obtained by HWCVD

“…Since the observation of intense photoluminescence from porous silicon (PS) at room temperature [1], properties of low dimensional silicon quantum structures have been a subject of extensive investigations [2,3]. Silicon-based nanostructures have been published so far with the majority devoted to the optical properties of nanocrystalline silicon embedded in SiO x films.…”

Phase Transformation of Monocrystalline Silicon Induced by Polishing With Diamond Abrasives

“…As the "local probe method" of structure, transmission election microscopy (TEM) and selected area electron diffraction (SAED) of the polishing residue were provided to investigate their phase structure and particle size [20]. Scanning electron microscope (SEM) is an intuitionistic detection method which can provide information of morphological structure, especially when the detected object is in nano-scale [21].…”