Porous silicon photoluminescence versus HF etching: No correlation with surface hydrogen species

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Abstract
The photoluminescence (PL) and infrared absorbance of electrochemically anodized, initially nonphotoluminescent, porous silicon samples were examined as a function of hydrofluoric acid (HF) etching time. Transmission Fourier transform infrared spectroscopy measurements revealed that the infrared absorbance from silicon hydrogen surface species immediately decreased with HF etching. In contrast, the PL did not appear until after HF etching times of 20–80 min, depending on initial sample porosity. Subsequently, the PL intensity increased, reached a maximum, and then progressively decreased versus HF etching time. These HF etching results demonstrate that there is no direct correlation between the PL and the silicon hydrogen surface species.