heubuisch besuch

diff --git a/posic/publications/sic_prec.tex b/posic/publications/sic_prec.tex
index 7d481b5..614be92 100644 (file)
--- a/posic/publications/sic_prec.tex
+++ b/posic/publications/sic_prec.tex
@@ -353,22 +353,32 @@ It turned out that the EA potential still favors a C$_{\text{i}}$ \hkl<1 0 0> DB
 
 MD simulations at temperatures used in IBS resulted in structures that were dominated by the C$_{\text{i}}$ \hkl<1 0 0> DB and its combinations if C is inserted into the total volume.
 Incoorporation into volmes $V_2$ and $V_3$ led to an amorphous SiC-like structure within the respective volume.
-To compensate overestimated diffusion barriers we performed simulations at elevated temperatures.
-TOOD: High C conc simulations ... then low:
-Time scales are still too low to observe C agglomeration sufficient for SiC precipitation, which is attributed to the slow phase space propagation inherent to MD in general.
+To compensate overestimated diffusion barriers we performed simulations at accordingly increased temperatures.
+No significant change was observed for high C concentrations.
+The amorphous phase is maintained.
+Due to the incoorparation of a huge amount of C into a small volume within a short period of time damage is produced, which obviously decelerates strcutural evolution.
+For the low C concentrations, time scales are still too low to observe C agglomeration sufficient for SiC precipitation, which is attributed to the slow phase space propagation inherent to MD in general.
 However, we observed a phase tranisiton of the C$_{\text{i}}$-dominated into a clearly C$_{\text{s}}$-dominated structure.
 The amount of substitutionally occupied C atoms increases with increasing temperature.
-Entropic contributions are assumed to be responsible for these structures that deviate from the ground state at 0 K.
-Indeed, in a previous ab initio MD simulation\cite{zirkelbach10b} performed at \unit[900]{$^{\text{C}}$} we observed the departing of a Si$_{\text{i}}$ \hkl<1 1 0> DB located next to a C$_{\text{s}}$ atom instead of a recombination into the ground state configuration, i.e. a C$_{\text{i}}$ \hkl<1 0 0> DB.
-
-Thus, we prpopose (support) the follwing model ...
-Sii stress compensation and vehicle
-
-Concluded that C sub is very probable ...
-Alignment lost, successive substitution more probable to end up with topotactic 3C-SiC.
-
-Both, low and high, acceleration not enough to either observe C agglomeration or amorphous to crystalline transition ...
-
+Entropic contributions are assumed to be responsible for these structures at eleveated temperatures that deviate from the ground state at 0 K.
+Indeed, in a previous ab initio MD simulation\cite{zirkelbach10b} performed at \unit[900]{$^{\circ}$C} we observed the departing of a Si$_{\text{i}}$ \hkl<1 1 0> DB located next to a C$_{\text{s}}$ atom instead of a recombination into the ground state configuration, i.e. a C$_{\text{i}}$ \hkl<1 0 0> DB.
+Ci to Cs by increased temperatures ...\cite{eichhorn99}
+Increased temperatures during implantation more efficient than postannealing methods, which reflects the present problems of low temperature and low time strcutural evolution ...\cite{eichhorn02}
+C-C for low temperatures, postannealing no that efficient as for high C implantations ...\cite{deguchi92}
+
+Thus, we propose an increased participation of C$_{\text{s}}$ already in the initial stages of the precipitation process.
+Thermally activated, C$_{\text{i}}$ is enabled to turn into C$_{\text{s}}$ accompanied by Si$_{\text{i}}$.
+The associated emission of Si$_{\text{i}}$ is needed for several reasons.
+For the agglomeration and rearrangement of C Si$_{\text{i}}$ is needed to turn C$_{\text{s}}$ into highly mobile C$_{\text{i}}$ again.
+Since the conversion of a coherent SiC structure, i.e. C$_{\text{s}}$ occupying the Si lattice sites of one of the two fcc lattices that build up the c-Si diamond lattice, into incoherent SiC is accompanied by a reduction in volume, large amount of strain is assumed to reside in the coherent as well as incoherent structure.
+Si$_{\text{i}}$ serves either as supply of Si atoms needed in the surrounding of the contracted precipitates or as interstitial defect minimizing the emerging strain energy of a coherent precipitate.
+The latter has been directly identified in the present simulation study, i.e. structures of two C$_{\text{s}}$ atoms with one being slightly displaced by a next neighbored Si$_{\text{i}}$ atom.
+
+It is, thus, concluded that precipitation occurs by successive agglomeration of C$_{\text{s}}$ as already proposed by Nejim et~al.\cite{nejim95}.
+This agrees well with a previous ab inito study on defects in C implanted Si\cite{zirkelbach10b}, which showed C$_{\text{s}}$ to occur in all probability.
+However, agglomeration and rearrangement is enabled by mobile C$_{\text{i}}$, which has to be present at the same time and is formed by recombination of C$_{\text{s}}$ and Si$_{\text{i}}$.
+In contrast to assumptions of an abrupt precipitation of an agglomerate of C$_{\text{i}}$\cite{werner96,werner97,eichhorn99,lindner99_2,koegler03}, however, structural evolution is believed to occur by a successive occupation of usual Si lattice sites with substitutional C.
+This mechanism satisfies the experimentally observed alignment of the \hkl(h k l) planes of the precipitate and the substrate, whereas there is no obvious reason for the topotactic orientation of an agglomerate consisting exclusively of C-Si dimers, which would necessarily involve a much more profound change in structure for the transition into SiC.
 
 \section{Summary}