Structural changes of porous silicon surface with thermal annealing studied by Si-29 nuclear magnetic resonance spectroscopy and fourier transform infrared spectroscopy

Si-29 nuclear magnetic resonance (NMR) spectra and infrared spectra were me asured for as-prepared and annealed porous silicon (PS) samples to characte rize the change of PS structure. Annealing changed the infrared spectra rem arkably: after 4-h annealing, the signals due to SiH2 disappeared and the i ntensity of the signals due to SiH decreased. On the other hand, the Si-29 NMR spectra with magic-angle spinning (MAS) were not much affected by the a nnealing. The linewidth of spectra without MAS, however, increased with ann ealing time with the peak location unchanged. Annealing caused hydrogen on the PS surface to be desorbed, especially in the case of SiH2 species, and (SiH)(2) dimer structure was produced during the annealing.