Optical Absorption, Photoluminescence, and Raman Scattering Studies on Si Nanowire Arrays Formed in Ag2SO4−HF−H2O Solution

Abstract

Vertically well-aligned Si nanowire (SiNW) arrays were synthesized by catalytic etching in a newly developed etchant system Ag2SO4−HF−H2O. The structural and optical properties of the synthesized SiNW arrays were investigated by scanning electron microscopy observation, Fourier-transform infrared (FTIR) spectroscopy analysis, near-IR−UV transmittance, Raman scattering, and photoluminescence (PL) measurements. The FTIR and transmittance measurements revealed that the SiNW arrays show about two or three orders lower optical transmittances in the far-IR−UV region than those for the single-crystalline Si substrate. The Raman intensities and spectral features were also found to be clearly different from those for the bulk single-crystalline Si. Such Raman scattering data were analyzed using a modified Lorentzian model with introducing an exponential asymmetry factor. Results were in satisfactory agreement with the experimental spectra. The SiNWs formed in the conventional AgNO3 solutions emitted lights in the red spectral region; however, no PL emission was observed from the Ag2SO4-synthesized SiNW array. This fact suggests that the Ag2SO4-synthesized nanowire sidewalls should be much smoother than the conventional AgNO3-synthesized ones.