Synchrotron-based analytical microprobe techniques, electron backscatter diffraction, and defect etching are combined to determine the dependence of metal silicide precipitate formation on grain boundary character and microstructure in multicrystalline silicon (mc-Si). Metal silicide precipitate decoration is observed to increase with decreasing atomic coincidence within the grain boundary plane (increasing Σ values). A few low-Σ boundaries contain anomalously high metal precipitate concentrations, concomitant with heavy dislocation decoration. These results provide direct experimental evidence that the degree of interaction between metals and structural defects in mc-Si can vary as a function of microstructure, with implications for mc-Si device performance and processing.

Crystals of LiZnP, LiCdP, and LiZnAs are prepared by direct fusion of constituent elements. All three materials are found to be p-type semiconductors. Absorption edge and photoconductivity spectra are measured. Band gaps are estimated to be 1.25 eV for LiZnAs, 1.3 eV for LiCdP, and 2.1 eV for LiZnP.

Quantitative data are presented that show partial ionic conductivity of Cu or Ag in ternary and quaternary electronic semiconductors, with idealized stoichiometry Cu,Ag,,InSe2. A trend of increasing facility of ionic motion with increasing Ag content was observed. Ionic transference numbers up to 0.13 and 0.55 were measured for CUI-and AgInSq,, respectively. This trend can be correlated with the degree of compactness of the structure. It is supported by results from measurements of effective values of chemical diffusion coefficients, obtained by a potentiostatic current decay technique. Those results show a generally higher diffusivity in AgInSe, than in CuInSe2 A clear trend of increasing diffusion coefficient (up to lO-' cm2/s) with decreasing concentration of IB metal was observed. No obvious general correlation is seen between net electronic carrier concentration (or resistivity) and diffusion coefficients, except that overall the highest diffusion coefficients are found for Cu-poor (or Ag-poor) samples which are also the most resistive. The effect of temperature (between 20 and 100 "C) on the diffusivity is small. On the basis of our observations we conclude that diffusion occurs predominantly via a vacancy mechanism and suggest that this possibility of coexistence of significant ionic mobility with true semiconductivity can be useful for electronic doping by native defects.

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