in the bulk utter unncaling in forming gas but not after high tempemture ( 1100"C) anneaIs in Ar. The presence of hydrogen dmmatical[y incrcascs the broad PL band centered in the near-infmred after tinncaling Lit1100"C but htis almost no effect on the PL spectral distribution. Hydrogen is found to sclccti~cly trap in the region where Si nanocrystais are formed, consistent with a model of H ptissivatin: surfucc states tit the Si/SiO: interface that leads to enhanced PL. The thermal stabiIity of the tmppul H and the PL yield observed ufter a high temperature anneal have been studied. The hydrogen concentration and PL yield are unchanged for subsequent anneals up to 400"C. However, ubovc -IO(YCthe PL decreases tind a more complicated H chemistry is evident. Similar concentmtions of H or D ure tmpped after annealing in HJ or Dj forming gas; however, no differences in the PL yield or spcctrtil distribution tire observed, indicating that the electronic transitions resulting in luminescence are not dependent on the moss of the hydrogen species.
Ion implantation damage and annealing results are presented for a number of crystalline oxides. In A12 O3, the amorphous phase produced by ion bombardment of the pure material first crystallizes in the (crystalline) γ phase. This is followed by the transformation of γ-Al2 O3 to α-A12O3 at a well defined interface. The activation energy for the growth of α alumina from γ is 3.6 eV/atom. In CaTiO3, the implantation-induced amorphous phase transforms to the crystalline phase by solid-phase epitaxy (SPE). ZnO is observed to remain crystalline even after high implantation doses at liquid nitrogen temperatures. The near surface of KTaO3 is transformed to a polycrystalline state after implantation at room temperature or liquid nitrogen temperature.
The dependence of the nonequilibrium partition coefficient k of Bi in Si upon solidification velocity v has been measured with sufficient accuracy to distinguish between proposed solute-trapping mechanisms. For the range of measured velocities, 2-14 m/s, we observe a much more gradual increase in k with increasing v than those previously reported and no evidence for a "saturation" effect, i.e., dk/dv-" 0 at k < 1. The continuous-growth model of Aziz fits the data quite well; the Aziz stepwise-growth model and the two-level Baker model yield values of dk/dv that are too high.
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