Spin–lattice relaxation of 29Si near porous silicon surface

The spin–lattice relaxations of 29Si at room temperature for as-prepared, annealed, and oxidized porous silicon PS. surfaces have been investigated. Monoexponential decays fitted well for as-prepared and annealed PS samples. The relaxation times of as-prepared and annealed PS samples were 220 and 190 s, respectively. The relaxations occur through the dipolar coupling with 1H. On the other hand, monoexponential decays were not observed for oxidized PS. Assuming that the decays obey an empirical stretched exponential decay function, O3SiH showed the relaxation time of 100 s and the relaxation time of SiO2 was 150 s. The dipolar coupling with proton contributes to the relaxation of O3SiH. The relaxation of 29Si spin is dominated by chemical shift anisotropy for SiO2. The oxidized PS showed the different relaxation behaviors from other PSs: short relaxation time, nonexponential decay, and the detection of silicons, which do not have direct bonding to proton. These behaviors are due to the oxygen incorporation in PS layer. q2000 Elsevier Science B.V. All rights reserved.