NOVEL TECHNIQUE FOR PREPARATION OF POROUS SILICON

Porous silicon (PS) was prepared by hydrothermal treatment of silicon in LiF-containing nitric acid solution. Scanning tunneling microscope (STM) studies show that the PS layers were uniform, and consisted of c olumns with cross-sectional diameters significantly less than 10 nm. T he luminescence measurement revealed that the wavelength of the photol uminescence (PL) peaks was at 690 nm, which was somewhat shifted towar d the higher energy side as compared with that of the porous silicon o btained by anodic etching. A blue band around 430 nm appeared after ra pid thermal oxidation (RTO) of the hydrothermally etched sample in air at 950 degrees C for 30 s. These results are interpreted in the light of the present theories suggested.