Three kinds of methods (0.08 mol/L iodine in ethanol, SiNx:H, and 40% HF) are used to passivate solar-grade Czochralski (Cz) silicon wafers. Thereafter, minority carrier lifetime and Fe-B pair density of the wafers are measured using the microwave photo-conductance decay (μ-PCD) technique. Based on the measured minority carrier lifetime, it is found that the passivation quality achieved by 0.08 mol/L iodine in ethanol is the best, while that by 40% HF solution is the worst. For the identical wafer, the density distribution of Fe-B pairs is different when different passivation methods are used. When the wafers are passivated by SiNx:H, there exists a close correlation between the distribution of minority carrier lifetime and the concentration distribution of Fe-B pairs. Furthermore, for wafers with high-quality passivation, there is a strong correlation between the recombination center concentration and the Fe-B pair density. All the analyses verify that the surface passivation quality of wafers influences the measurement results of minority carrier lifetime, Fe-B pair density and recombination center concentration.
LI FengMA ZhongQuanMENG XiaJieLU PengYU ZhengShanHE Bo
In this paper,we study the effect of spherical aberrations on the light intensity and the temperature distribution in the focal region in a 250-kHz femtosecond laser irradiated Ag +-doped borosilicate glass.When a focused beam goes through an interface between air and glass,spherical aberration will result in the separation of the focal point and then cause a clear change of the light intensity distribution along the incident direction.That phenomenon will further influence the longitudinal cross-section temperature distribution in glass.Here we use Ag nanoparticle formation as a marker for establishing temperature distribution and we find that the formation of nanoparticle shows a strong dependence on the temperature field and the detailed precipitation process is also discussed.
