We report a study on gamma irradiated porous Si. The electron paramagnetic resonance study on porous Si irradiated by gamma rays shows that the observed signals come from an intrinsic defect, a Si dangling bond, at the interface of Si/SiOx in porous Si. The photoluminescence measurements show that the gamma irradiation not only increases the intensity of the photoluminescence but also greatly improves its stability. The spectra of the Fourier transform infrared absorption show that the gamma irradiation is an effective method for accelerating oxidation of porous Si. All experimental results can be explained by the increase of the oxidation layer thickness which decreases the nonradiative recombination probability of electron-hole pairs.

A hydrogen-induced infrared absorption band located around 1835.4 cm-' is observed in protonimplanted GaAs single crystal at 4.2 K and identified as a hydrogen localized vibrational mode (LVM). The dependence of absorption intensity, linewidth, and frequency of the hydrogen LVM on temperature is presented for the first time. Both, the linewidth and frequency shift due to temperature variation are much larger than those of the hydrogen-

We have achieved production of porous silicon (PS) that emits blue light at a peak wavelength of 460 nm. On storing it in air for three months. or illuminating if with the 365 nm line of a uv lamp, its photoluminescence intensity and pe& wavelength remain stable. With Fourier-msform infmed (mR) measurements, we have studied the surface chemical bonds of the Ps emitting blue light. and compared i u FrIR specvum with those of the as-prepared PS emihing red-orange light, and those of the processed PS emitting no light. We consider that the blue light emission originates from the SiO, layers covering nanoswle silicon units in PS.

We have studied the effect of laser illumination (argon laser line of 488 nm) on the oxidization process of the inner surfaces of porous silicon (PS) by measuring the photoluminescence (PL), Fourier-transform infrared (FTIR) absorption and x-ray photoelectron spectroscope and contrasted the variations of PL and FTIR spectra of the PS treated in the following four ways: 1. In vacuum with laser illumination (LI) with power density of 12 mW / mm2. 2. In oxygen with LI. 3. In oxygen without LI. The times for all the above three treatments were 1 h. 4. Storage in air for 2 months without LI. The PL peak of PS showed serious degradation and a blue shift in case 2 but only a moderate degradation and no shift in case 1. The results of FTIR absorption show that the LI in an atmosphere of oxygen enhanced greatly the increase of oxygen-related absorption bands and the decrease of various silicon-hydrogen vibrational mode absorption bands.