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Silicon (Si) films were obtained through aluminothermic reduction of the quartz (SiO2) substrates, where the surface of the quartz in contact with the deposited aluminum (Al) layer has been converted to film Si during high-temperature annealing following reduction reaction. X-ray diffraction (XRD) patterns and Raman spectra show dominating peaks corresponding to elemental Si in the obtained films. Energy dispersive spectroscopy (EDS), as well as XRD of the obtained Si layer, suggests that reduction products consist of mainly elemental Si mixed with oxides of Al-related phases. Both the higher reaction temperature and high initial Al-content (larger thickness of Al film in Al/SiO2 structure), studied in this paper, were found in favor of obtaining higher contents of Si in the obtained films. Thus, crystallinity and quality of the obtained Si-layer improve with the increase of both reduction temperature as well as thickness of the Al layer, as confirmed by XRD and Raman spectra. The aluminothermic reduction mechanism has been discussed using XRD as well as a ternary phase diagram of the constituent elements, obtained from EDS data. Crystalline nature (nanocrystal to microcrystal to polycrystal) and the crystalline quality of the obtained Si layers were found to be affected by the thickness of the deposited Al layer on SiO2 substrates.

Silicon (Si) films were deposited on low-cost graphite substrates by the electrochemical reduction of silicon dioxide nanoparticles (nano-SiO2) in calcium chloride (CaCl2), melted at 855 °C. Cyclic voltammetry (CV) was used to analyze the electrochemical reduction mechanism of SiO2 to form Si deposits on the graphite substrate. X-ray diffraction (XRD) along with Raman and photoluminescence (PL) results show that the crystallinity of the electrodeposited Si-films was improved with an increase of the applied reduction potential during the electrochemical process. Scanning electron microscopy (SEM) reveals that the size, shape, and morphology of the Si-layers can be controlled from Si nanowires to the microcrystalline Si particles by controlling the reduction potentials. In addition, the morphology of the obtained Si-layers seems to be correlated with both the substrate materials and particle size of the feed materials. Thus, the difference in the electron transfer rate at substrate/nano-SiO2 interface due to different applied reduction potentials along with the dissolution rate of SiO2 particles during the electrochemical reduction process were found to be crucial in determining the microstructural properties of the Si-films.