slide 16
-
+implantation of highly energetic carbon atoms results in a multiplicity
+of possible point defects and respective combinations.
+thus, in the following, defect combinations of an initial carbon interstitial
+and further types of defects,
+created at certain neighbor positions, numbered 1-5, are investigated.
+the investigations are restricted to dft calculations.
+energetically favorable and unfavorable configurations,
+determined by the binding energies,
+can be explained by stress compensation and increase respetively.
+
+as can be seen, the agglomeration of interstitial carbon is energetically
+favorable.
+indeed, the most favorable configuration shows a strong C-C bond.
+however, due to high migration barriers or energetically unfavorable
+intermediate configurations to obtain this configuration,
+only a low probability is assumed for C-C clustering.
+
+in contrast, for the second most favorable configuration,
+a migration path with a low barrier exists.
+moreover, within the systematically investigated configuration space,
+this type of defect pair is represented two times more often
+than the ground state.
+
+the results suggest that agglomeration of Ci indeed is expected.
slide 17
+
+this is reinforced by the plot of the binding energy of Ci dbs
+separated along the 110 direction with respect to the C-C distance.
+the interaction is found to be proportional to the reciprocal cube
+of the distance for extended separations and saturates for the smallest
+possible distance, i.e. the ground state.
+a capture radius clearly extending 1 nm is observed.
+the interpolated graph suggests the disappearance of attractive forces
+between the two lowest separation distances of the defects.
+
+this supports the assumption of C agglomeration and the absence of C clustering.
+
slide 18
+
+if a vacancy is created next to the Ci defect,
+a situation absolutely conceivable in ibs,
+the obtained structure will most likely turn into the Cs configuration.
+if the vacancy is created at position 1, the Cs configuration is directly
+obtained in the relaxation process.
+if it is created at other positions, e.g. 2 and 3,
+only low barriers into the Cs configuration exist
+and high barriers are necessary for the reverse process.
+
+based on this, a high probability for the formation of Cs,
+which is found to be extremely stable, must be concluded.
+
slide 19
+
+in addition, it is instructive to look at combinations of Cs and Si_i,
+again, a situation which is very likely to arise due to implantation.
+Cs located right next to the 110 Si db within the 110 chain
+constitutes the energetically most favirable configuration,
+which, however, is still less favorable than the Ci 100 db,
+in which the silicon and carbon atom share a single lattice site.
+however, the interaction of C_s and Si_i drops quickly to zero
+indicating a low capture radius.
+in ibs, configurations exceedinig this separation distance are easily produced.
+thus, Cs and Si_i, which do not react into the ground state,
+constitute most likely configurations to be found in ibs.
+
+this is supported by a low migration barrier necessary for the transition
+from the ground state Ci 100 db into the configuration of Cs and Si_i.
+in addition, a low migration barrier of the interstitial silicon,
+enables configurations of further separated Cs and Si_i defects.
+
+in total, these findings demonstrate that configurations of Cs and a Si_i db,
+instead of the thermodynamic ground state, play an important role in ibs,
+which indeed constitutes a process far from equilibrium.
+
slide 20
+
+once more, this is supported by results of an ab inito md simulation at 900 dc.
+the initial configuration of Cs and Si_i does not recombine into the gs,
+instead, the defects are separated by more than 4 neighbor distances
+realized in a repeated migration mechanism of annihilating and arising Si_i dbs.
+
+clearly, at higher temperatures, the contribution of entropy
+to structural formation increases, which might result in a spatial separation,
+even for defects located within the capture radius.
+
+to conclude, the results of the investigations of defect combinations
+suggest an increased participation of Cs in the precipitation process.
+
slide 21
+
+now ...
+
slide 22
slide 23
slide 24
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