FORMATION OF LUMINESCENCE POROUS SILICON BY 2-STEP CHEMICAL IMMERSIONAND ROLE OF NO2 IN ETCHING

The uniform luminescent porous silicon (PS) film on crystal Si wafer h as been prepared by two-step chemical staining etching. The refractive index of the film ranges from 2.0 to 2.4. The photoluminescence (PL) and photoluminescence excitation (PLE) spectra and Fourier transform i nfrared (FTIR) spectra have been measured. The features of chemically stained PS are consistent with those of anodized samples. It is found that the etching is induced by the electron transmitting through neutr al NO2. Both oxidization by HNO2 and hydrogen action by HF make the ch emically stained PS have similar FTIR spectra as anodized samples. The occurrence of bold spots during PS formation has been discussed. It i s believed that there exists metasilicate acid in the PS film.