Microstructure and light emitting in porous silicon derived from hydrothermal etching

Light emitting porous silicon (PS) was prepared by hydrothermal etching of P-type single-crystal silicon. Red (690 nm), blue (430 nm) photoluminescence (PL) samples can be obtained respectively by controlling etching condition. Scanning Tunneling Microscopy (STM) image of the PS layer shows individual uniform columns exist throughout the structure. High-resolution Electron Microscopy (HREM) image further shows these columns are amorphous phase with nanocrystallites (5nm) embedded, confirmed to be SiO2 and silicon nanocrystallites, respectively. X-ray diffraction (XRD) study shows these silicon nanocrystallites have lattice distortion. Photoluminescence in PS is suggested to be aroused from quantum confinement in these distorted nanocrystallites, and PL wavelength variation with preparation was interpreted on the basis of microstructure studies. Nondegrading PL in PS can be obtained by iron-passivating of surface of silicon nanocrystallites, confirmed to be the formation of Fe-Si bonds on the surface of silicon nanocrystallites.