High S/N crystallinity measurement and effective defect passivation in silicon nanostructures for third generation photovoltaics

For application of Si nanostructures to third generation photovoltaics, high S/N measurement of Si crystallinity and effective defect passivation method have been investigated. Here we use Si/SiO₂ multiple quantum wells as an example of nanostructure, and show that attenuated total reflectance FTIR (ATR-FTIR) spectroscopy can be applied to detect crystallization of Si with high sensitivity based on the dependence of silicon-hydrogen absorbance peaks on Si crystal face. ATR-FTIR technique, which probes the very surface of samples, was found to be more sensitive to crystallization than Raman spectroscopy. We also show that high-temperature hydrogen annealing is an effective defect passivation method. In particular, the effectiveness of passivation of E´ center in SiO₂, which is essential to the solar cells involving tunneling through SiO₂, was demonstrated.