The precipitation of oxygen in silicon has been studied in the temperature range 650 to 1050 degrees C using the techniques of chemical etching, IR absorption applied to the 9 mu m band (4.2K), and small-angle neutron scattering (SANS). The IR data and etch pit counts, relating to the number densities of precipitate particles, have been fitted to Ham's theoretical model for the diffusion limited growth of randomly distributed particles. Full allowance is made for the increase in size of the precipitates with increasing time and good agreement is found over the complete period starting from zero time. Values of the diffusion coefficient of oxygen so determined are in excellent agreement with other data obtained by different methods, including SANS measurements at 750 degrees C described in the present work. The combined data give D=0.11 exp(-2.51 eV/kT) cm2s-1. The SANS data also indicate that the precipitates are not spherical in shape after a short initial period, and they show that the initial concentration of particles nucleated decreases with annealing time. The solid solubility cs(T) is determined at each temperature and compared with previous measurements. The authors conclude that the best combination of results leads to cs(T)=2.6*1022 exp(-1.4 eV/kT) down to 850 degrees C. At lower temperatures cs decreases more slowly with decreasing temperature, indicating a possible change in the structure or the form of the precipitated SiO2 phase.

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A comprehensive neutron scattering study has been performed of hydrogenated (SiH), deuterated (SiD) and partially fluorinated deuterated (SiDF) amorphous silicon, prepared by the glow-discharge technique. The measurements performed include diffraction, small-angle neutron scattering (SANS) and inelastic neutron scattering, and the data obtained are discussed in terms of various structural models in the literature. The real-space correlation function for SiD exhibits sharp peaks at 1.49 and 2.36 Å, due to Si-D and Si-Si covalent bonds, respectively, while peaks centred at 3.2 and 3.8 Å are due to Si-D and Si-Si second-neighbour distances. High-energy resolution inelastic scattering measurements for SiH show that there are approximately equal numbers of [Formula: see text] and = SiH groupings, there being no indication of excitations corresponding to -SiH groupings. The presence of molecular hydrogen is demonstrated unambiguously by the observation of the ortho-to-para conversion, via molecular rotation modes at 14.5 and 29.4 meV. The shift in the Si-H stretch modes introduced by deuteration is slightly less than the value of [Formula: see text] expected for free hydrogen, indicating a small but observable influence of the amorphous silicon matrix. The size of the cages containing the H molecules has been investigated via SANS, which yields a mean Guinier radius of ∼5-6 Å. In addition, the use of the H-D SANS contrast technique indicates that each cage contains on average about 60 H (D) molecules. The data for the SiDF sample are consistent with a previously suggested model of network cages predominantly containing molecular SiF.

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