| Summary: | 碩士 === 國立中央大學 === 機械工程研究所 === 91 ===
The photo-electrochemical behavior of n-type Si (100) in an ethanolic hydrofluoric acid (HF) has been investigated in this work. Dc-potentiodynamic polarization of the silicon, illuminated by a halogen lamp from its backside, was conducted in the HF solution containing ethanol or not. The voltammogram demonstrated that the anodic dissolution rate of the silicon in the HF solution was accelerated by the illumination. The etching rate was faster when the illumination power is intensified, and the HF concentration increased.
The effect of ethanol addition in the HF solution was also of interest. The electrochemical behavior of the silicon depicted that the presence of ethanol in the HF solution resulted in electro-polish inside the etching pits. Potentiostatic etching of the silicon, illuminated with a halogen lamp (50 W and 20,000 Lx), was conducted in 2 M HF solution containing a variety of ethanol at certain potentials selected from the anodic polarization diagram. Electrochemical impedance spectroscopy was also carried out in the same condition. The surface morphology on the etched silicon under various conditions was examined by scanning electron microscopy (SEM), and the surface roughness was evaluated by atomic force microscopy (AFM).
The open circuit potential (OCP) for the silicon, illuminated with lamp and immersed in various solutions, was measured. Further checking the results from EIS at OCP, one concluded that illumination and ethanol-addition are advantageous to preparation of macro-porous silicon.
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