defects nearly finished, long time scale simulations started

[lectures/latex.git] / posic / thesis / defects.tex

diff --git a/posic/thesis/defects.tex b/posic/thesis/defects.tex
index 7b81390..4164f87 100644 (file)
--- a/posic/thesis/defects.tex
+++ b/posic/thesis/defects.tex
@@ -1299,7 +1299,7 @@ In total 10 different configurations exist within the investigated range.
 \begin{center}
 \includegraphics[width=12cm]{c_sub_si110.ps}
 \end{center}
-\caption{Binding energy of combinations of a substitutional C and a Si \hkl<1 1 0> dumbbell self-interstitial with respect to the separation distance.}
+\caption[Binding energy of combinations of a substitutional C and a Si \hkl<1 1 0> dumbbell self-interstitial with respect to the separation distance.]{Binding energy of combinations of a substitutional C and a Si \hkl<1 1 0> dumbbell self-interstitial with respect to the separation distance. The binding energy of the defect pair is well approximated by a Lennard-Jones 6-12 potential, which is used for curve fitting.}
 \label{fig:defects:csub_si110}
 \end{figure}
 According to the formation energies none of the investigated structures is energetically preferred over the C-Si \hkl<1 0 0> dumbbell interstitial, which exhibits a formation energy of 3.88 eV.
@@ -1308,10 +1308,12 @@ This is affirmed by the plot of the binding energies with respect to the separat
 Thus, the C-Si \hkl<1 0 0> dumbbell structure remains the ground state configuration of a C interstitial in c-Si with a constant number of Si atoms.
 
 {\color{blue}
-However the binding energy quickly drops to zero with respect of the distance indicating a possibly low interaction capture radius of the defect pair.
+However the binding energy quickly drops to zero with respect to the distance, which is reinforced by the Lennard-Jones fit estimating almost zero interaction energy already at 0.6 nm.
+This indicates a possibly low interaction capture radius of the defect pair.
 Highly energetic collisions in the IBS process might result in separations of these defects exceeding the capture radius.
 For this reason situations most likely occur in which the configuration of substitutional C can be considered without a nearby interacting Si self-interstitial and, thus, unable to form a thermodynamically more stable C-Si \hkl<1 0 0> dumbbell configuration.
 }
+\label{section:defects:noneq_process_01}
 
 The energetically most favorable configuration of the combined structures is the one with the substitutional C atom located next to the \hkl<1 1 0> interstitial along the \hkl<1 1 0> direction (configuration \RM{1}).
 Compressive stress along the \hkl<1 1 0> direction originating from the Si \hkl<1 1 0> self-intesrtitial is partially compensated by tensile stress resulting from substitutional C occupying the neighboured Si lattice site.
@@ -1434,6 +1436,7 @@ Thus, carbon interstitials and vacancies located close together are assumed to e
 
 While first results support the proposed precipitation model the latter suggest the formation of silicon carbide by succesive creation of substitutional carbon instead of the agglomeration of C-Si dumbbell interstitials followed by an abrupt transition.
 Prevailing conditions in the IBS process at elevated temperatures and the fact that IBS is a nonequilibrium process reinforce the possibility of formation of substitutional C instead of the thermodynamically stable C-Si dumbbell interstitials predicted by simulations at zero Kelvin.
+\label{section:defects:noneq_process_02}
 
 {\color{blue}
 In addition, there are experimental findings, which might be exploited to reinforce the non-validity of the proposed precipitation model.