Papers by Keyword: Metal Impurities

Abstract: A YAG continue-wave laser has been used to refine the surface of silicon wafers in this study. During laser scanning, the irradiated region of the surface of the wafer experienced melting and subsequent recrystallization, which results in a redistribution of metal impurities in the molten pool along the depth direction. Cross-sectional micrographs of irradiated wafers have a clear boundary, which confirms the process of recrystallization, and the depth of molten region depends on the scanning parameters and the size of wafer. Secondary ion mass spectrometry measurements have been carried out to characterize the concentration of metal impurities. After redistribution of metal impurities, a final relative purity region was formed close to the surface. SIMS measurements demonstrate that the metal impurity concentration of the purity region has significantly reduced. The mechanism of the redistribution process of metal impurities in the molten pool has been qualitatively analyzed. All of the experimental results support that the CW laser scanning technology can effectively refine the specific surfaces of silicon wafers, and this technology has a great potential in the field of solar cells.

Abstract: Electron beam injection(EBI) is a process of gathering the electrons in materials using electron beam(EB). The EBI technology is proposed for purification of silicon particles by removing metal impurities through high-temperature oxidation, EBI, and HF acid washing processes. Analysis of silicon particle morphology after high-temperature oxidation using digital camera and after EBI using scanning electron microscope(SEM) were conducted. Then, the composition of silicon particles was analyzed using inductively coupled plasma(ICP). The silicon particle colours turned bright after EBI; therefore, EBI can change the thickness of SiO2 films in addition to increasing the temperature of the silicon particles. The results show that this technology is effective in removing metal impurities in silicon particles.