| Summary: | 碩士 === 國立中央大學 === 機械工程學系 === 107 === In this study, we perform cryogenic laser-assisted electrochemical etching on heavily doped p-type silicon wafer, and observe the influence of low temperature. Since the carrier mobility of silicon wafer is about 120(cm2/V•s) at room temperature, 108(cm2/V•s) at -20℃, the mobility reduces while temperature decrease. Therefore, the etching experiments are performing at room temperature(25℃),-20℃(dry ice), and using scanning electron microscope(SEM), transmission electron microscope(TEM) and photoluminescence(PL) to observe the structure and characteristics of porous silicon. We find that the lower the temperature, the smaller the nanocrystals grain, and the phenomenon of blue-shift is shown in the result of PL.
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