From 32e7d1d9c2f05b0e3a6eff26008f1530ce4667a3 Mon Sep 17 00:00:00 2001 From: hackbard Date: Fri, 26 Feb 2010 16:21:19 +0100 Subject: [PATCH] revolution now! --- posic/thesis/defects.tex | 27 +++++++++++++++++---------- 1 file changed, 17 insertions(+), 10 deletions(-) diff --git a/posic/thesis/defects.tex b/posic/thesis/defects.tex index d186153..0f09f03 100644 --- a/posic/thesis/defects.tex +++ b/posic/thesis/defects.tex @@ -693,7 +693,7 @@ Relative silicon neighbour positions: & 1 & 2 & 3 & 4 & 5 & R\\ \hline \hkl<0 0 -1> & {\color{red}-0.08} & -1.15 & {\color{red}-0.08} & 0.04 & -1.66 & -0.19\\ - \hkl<0 0 1> & 0.34 & 0.004 & -2.05 & 0.26 & -1.53 & -\\ + \hkl<0 0 1> & 0.34 & 0.004 & -2.05 & 0.26 & -1.53 & -0.19\\ \hkl<0 -1 0> & {\color{orange}-2.39} & -2.16 & {\color{green}-0.10} & {\color{blue}-0.27} & {\color{magenta}-1.88} & -0.09\\ \hkl<0 1 0> & {\color{cyan}-2.25} & -0.36 & {\color{cyan}-2.25} & {\color{purple}-0.12} & {\color{violet}-1.38} & -\\ \hkl<-1 0 0> & {\color{orange}-2.39} & -1.90 & {\color{cyan}-2.25} & {\color{purple}-0.12} & {\color{magenta}-1.88} & -\\ @@ -760,26 +760,33 @@ This bond has a length of 1.38 \AA{} close to the nex neighbour distance in diam The minimum of binding energy observed for this configuration suggests prefered C clustering as a competing mechnism to the C-Si dumbbell interstitial agglomeration inevitable for the SiC precipitation. Todo: Activation energy to obtain a configuration of separated C atoms again or vice versa to obtain this configuration from separated C confs? However, for the second most favorable configuration, presented in figure \ref{fig:defects:comb_db_01} a), the amount of possibilities for this configuration is twice as high. -In this configuration the two carbon atoms are spaced by 2.70 \AA. -The initial Si (I) and C (I) dumbbell atoms are displaced along \hkl<1 0 0> and \hkl<-1 0 0> in such a way that the Si atom is forming tetrahedral bonds with two silicon and two carbon atoms. +In this configuration the initial Si (I) and C (I) dumbbell atoms are displaced along \hkl<1 0 0> and \hkl<-1 0 0> in such a way that the Si atom is forming tetrahedral bonds with two silicon and two carbon atoms. The carbon and silicon atom constituting the second defect are as well displaced in such a way, that the carbon atom forms tetrahedral bonds with four silicon neighbours, a configuration expected in silicon carbide. +The two carbon atoms spaced by 2.70 \AA{} do not form a bond but anyhow reside in a shorter distance as expected in silicon carbide. The Si atom numbered 2 is pushed towards the carbon atom, which results in the breaking of the bond to atom 4. The breaking of the $\sigma$ bond is indeed confirmed by investigating the charge density isosurface of this configuration. -Todo: But is this configuration beneficial for SiC prec? +Todo: Is this conf really benificial for SiC prec? -001 at pos 2 looks as if there is no interaction. -There is an interaction but in the same time strain is reduced due to the opposing orientations of the defects, which leads to this low energy value. +Figure \ref{} shows the next three configurations energetically favored. +-2.16 ... next to correct C-Si also a nicely C-C distance observed! +sth similar to C-Si 110 db without delta h due to the involevment of initial c int atom. -Explanation of results of defects created along <110>. +-2.05 ... both C atoms correctly coordinated, however (check C-C distance, too close?) wrong coordination of the C-Si-C bonds which reside in a plane ... all the 4 participating atoms reside in a plane ... --1.90 ... +-1.90 ... again, one C atom bound to 4 Si atoms but the second one only bond to three Si atoms. However, C-C slighlty higher. --2.16 ... +The 2.7 diatnce characteristic for configurations with one C atom bound to 4 silicon and. +Different energies due to slightly varying constellation. the more far-off ones: --0.27 and -0.12 ... +-0.27 and -0.12 ... carbon is threefold coordinated. +initial structures evident, seem to be independent of each other ... but better ... -1.88 and -1.38 ... +-1.38: Si (I) moves towards 2nd Si int in 110 direction, such that both Si 4fold coordinated and C remain 3fold ... +-1.88: threefold coordinated c atoms but all participating Si atoms fourfold coordinated ... + +Explanation of results of defects created along <110>. Minimum E (reorientation) per distance -- 2.39.2