Silicon Nanowires Prepared By Wet Chemical Etching Method

Because silicon is an indirect band-gap semiconductor, T=0K, the band gap width Eg=1.17eV, T=300K, the band gap width Eg=1.14eV, the conduction band bottom and valence band top are located in different location in the wave vector space. With the condition of conservation of momentum, electrons achieve an indirect band-gap semiconductor light-emitting transition only through phonons interaction. However, the one-dimensional silicon nanowires with a high surface activity and the quantum confinement effect can get strong fluorescence, thus the research on silicon nanowires is extremely important.In this paper, we use the selective etching method and wet chemical etching method to etch silicon, and hope to achieve nanoarray-structure. We discussed the effects of four growth conditions on the morphology of silicon nanowires, including the growth time, the concentration of hydrofluoric acid, the concentration of silver nitrate solution, the reaction temperature. We also discussed the effects of the concentration of hydrofluoric acid, the concentration of silver nitrate solution, the growth temperature on the Raman spectra of silicon nanowires.By analyzing the SEM images of silicon nanowires prepared under different conditions, we believe that the silicon nanowires prepared one hour under the reaction temperature 50℃, 5mol / L hydrofluoric acid, 0.02mol / L silver nitrate, and the volume ratio of hydrofluoric acid and silver nitrate the V (HF ): V ( AgNO 3) = 1:4, can achieve the best shape. The silicon nanowires form a typical structure of nanowire arrays, are about 30 microns in length and 15-50nm in diameter. According to its Raman spectrum, its main Raman peak is at 519.2 cm^-1, and its full wave at half maximum is 3.1 cm^-1.The silicon nanowires prepared under high concentrations of hydrofluoric acid and high growth temperature, have a large number of defects. Because the defects presenting in the samples, the phonon frequency was changed in silicon nanowires, as well as the lives of phonons were shortened and the full wave at half maximum increased. Thus we observed the full wave at half maximum(FWHM)of 5.5mol / L hydrofluoric acid samples was 7.6 cm^-1, as well as FWHM of the samples prepared under the 75℃growth temperature was up to 5.7 cm^-1 .