Estructura y morfología de películas de pm-Si:H crecidas por PECVD variando la dilución de diclorosilano con hidrógeno y la presión de trabajo

Abstract

Hydrogenated polymorphous silicon (pm-Si:H) is an attractive material for applications in the photovoltaic industry as it has optoelectronic properties similar to amorphous silicon (a-Si:H), which is the material currently used, and better stability to prolonged exposure to solar radiation. In this work we report experimental results of structural and morphological characterization of pm-Si:H films in terms of grain size and crystalline fraction obtained by Raman spectroscopy studies and the analysis of surface roughness with atomic force microscopy. The films were obtained by PECVD under conditions of generation of nano-crystalline silicon inclusions embedded in an amorphous silicon matrix. Changes in pressure of the reactor chamber (250 and 500 mTorr) and variations in the dilution of the silicon precursor gas (SiH$_{2}$Cl$_{2}$) with hydrogen (H$_{2}$) (flow rates of 25, 50, 75 and 100 sccm) modified the nanocrystals size and the crystalline fraction. The morphological analysis showed that for 25 sccm of H$_{2}$ there is a difference of 8 nm in the RMS roughness between both pressures, while for the other flows of H$_{2}$ the same RMS roughness (2 to 3 nm) was obtained. These results are very important because the optoelectronic properties of materials depend on the size and density of nanocrystals and the roughness analysis helps determine the growth conditions to produce high quality interfaces for application of the material in photovoltaic devices.