The formation of H*2 by electron-irradiation of hydrogenated Si

To clarify the formation mechanism of H-2* in Si; we studied the dependence of the concentration of HT on the electron-irradiation dose: in hydrogenated Si crystals. Specimens were prepared from high-purity, B-doped and C-doped Si crystals. They were doped with H by annealing in H-2 gas at 1300 degrees C followed by quenching. They were irradiated by 3 MV electrons at room temperature (RT). We measured their optical absorption spectra at 7 K by an fourier-transform infrared absorption spectroscopy (FT-IR) spectrometer. The intensity of the 1838 cm(-1) peak which is due to H-2* was found to be the weakest in C-doped Si, medium in B-doped Si and the strongest in high-purity Si. This tendency correlates with that of the intensity of the 2122 cm(-1) peak which is due to a complex of a vacancy and two H atoms. The. intensity of the 1838 cm(-1) peak linearly depends on the electron dose at low doses. These results suggest two mechanisms for the formation of H-2* from H-2, namely, a combination of a vacancy and an H-2 or a combination of a Frenkel pair and an H-2.