No abstract

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According to single-crystal threc-dimensional X-ray data, n-butyric acid crystals at -43 °C. are monoclinic with a=8.01_+0.08, b=6"82+0"02, c=10.14_+0.03A; fl--lll °27'_+15'.With 4 molecules per unit cell, the calculated density is 1.135 g.cm. -3. This structure exists from the melting point down to about -55 °C. where it changes to a second phase of unknown structure.The structure is described in space group C2/m. The molecules occur as dimers with the oxygen and carbon atoms in the mirror plane, but with large amplitudes for out-of-plane vibrations. A structure in space group C2 is not ruled out by the calculations, but is considered less likely than the structure in C2/m. The bond distances, after corrections of up to 0.03 A for thermal motion, are C-O = 1.22 and 1.35 /~, C-C = 1.54, 1"53 and 1-53 /~ (in order from carboxyl to methyl), each _+ 0.02 A. The hydrogen bond length is 2.62/~.

Gold was diffused into arsenic-doped silicon slices with initial resistivity of 0.3 or 5 Ω·cm at temperatures between 850° and 1250°C for times sufficiently long that the gold concentration was essentially constant, except for a very thin surface region which had a much larger concentration. The gold concentration was determined by means of neutron activation analysis. It was found that the gold concentrations were lower than would be expected from published solubility data when diffusion occurred at temperatures below 1100°C. Several surface treatments were found to result in similar gold concentrations when an evaporated gold film was used as the source. The measured room-temperature resistivity was found to be in fair agreement with computations using accepted values for the various silicon parameters and the gold energy levels. Although refinements in the calculations and improved experimental techniques are both still necessary, it has been shown that the qualitative features of the model on which the calculations are based are certainly correct. It has also been shown that gold diffusions in silicon with a moderate dislocation density can be carried out satisfactorily in an oxidizing atmosphere.