Low temperature manufacturing of Si nanocrystallites in the SiOx matrix applicable in solar cells

Abstract

Progress in fabrication and application of the nanocrystalline silicon thin films in opto-electronic devices like solar cells, thin film transistors, memory cells, etc., is a way to further enhance their parameters. Those films exhibit increased stability, absorption, carrier mobility. They also exhibit scattering and anti-/reflection properties. This paper is focused on the technology of manufacturing such films by means of Radio Frequency Plasma Enhanced Chemical Vapor Deposition (RF PECVD). The authors describe the manufacturing process based on periodical variation of the process parameters, such as hydrogen to silane ratio (Rh), gas flows, RF power and pressure in the process chamber, during the deposition process. Additionally, the influence of chamber pre-annealing on resulting type of matrix with nanocrystalline inclusions, a-Si:H or SiOx, and differences between them are discussed. The authors also present the Secondary Ion Mass Spectrometry (SIMS) analyses and the measurements of typical samples with High Resolution Transmission Electron Microscopy (HRTEM), which confirms the existence of the nanocrystallites in the a-Si:H or SiOx matrix.