X-Git-Url: https://hackdaworld.org/gitweb/?p=lectures%2Flatex.git;a=blobdiff_plain;f=posic%2Fthesis%2Fdefects.tex;h=ac2228801f04972435f3465986db5cde8697e170;hp=65cae0f540f1d296e6995dfa44977fd47cacdba9;hb=a3831cc8a0d5bd03cbc1b0907bd11168416fd4b2;hpb=6d1beb256b75bb20d1d5e50ca81ed4da17789daa diff --git a/posic/thesis/defects.tex b/posic/thesis/defects.tex index 65cae0f..ac22288 100644 --- a/posic/thesis/defects.tex +++ b/posic/thesis/defects.tex @@ -885,7 +885,7 @@ In the present study, a further relaxation of this defect structure is observed. The C atom of the second and the Si atom of the initial DB move towards each other forming a bond, which results in a somewhat lower binding energy of \unit[-2.25]{eV}. The corresponding defect structure is displayed in Fig.~\ref{fig:defects:225}. In this configuration the initial Si and C DB 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 Si and two C atoms. -The C and Si atom constituting the second defect are as well displaced in such a way, that the C atom forms tetrahedral bonds with four Si neighbors, a configuration expected in SiC. +The C and Si atom constituting the second defect are as well displaced in such a way that the C atom forms tetrahedral bonds with four Si neighbors, a configuration expected in SiC. The two carbon atoms, which are spaced by \unit[2.70]{\AA}, do not form a bond but anyhow reside in a shorter distance than expected in SiC. Si atom number 2 is pushed towards the C atom, which results in the breaking of the bond to Si atom number 4. Breaking of the $\sigma$ bond is indeed confirmed by investigating the charge density isosurface of this configuration. @@ -920,7 +920,7 @@ Instead, the Si atom forms a bond with the initial \ci{} and the second C atom f The C atoms are spaced by \unit[3.14]{\AA}, which is very close to the expected C-C next neighbor distance of \unit[3.08]{\AA} in SiC. Figure~\ref{fig:defects:205} displays the results of a \hkl[0 0 1] DB inserted at position 3. The binding energy is \unit[-2.05]{eV}. -Both DBs are tilted along the same direction remaining aligned in parallel and the second DB is pushed downwards in such a way, that the four DB atoms form a rhomboid. +Both DBs are tilted along the same direction remaining aligned in parallel and the second DB is pushed downwards in such a way that the four DB atoms form a rhomboid. Both C atoms form tetrahedral bonds to four Si atoms. However, Si atom number 1 and number 3, which are bound to the second \ci{} atom are also bound to the initial C atom. These four atoms of the rhomboid reside in a plane and, thus, do not match the situation in SiC. @@ -1229,7 +1229,7 @@ For the same reasons as in the last subsection, structures other than the ground %In case a) only the first displacement is compensated by the substitutional carbon atom. %This results in a somewhat higher binding energy of -0.51 eV. %The binding energy gets even higher in case b) ($E_{\text{b}}=-0.15\text{ eV}$), in which the substitutional carbon is located further away from the initial dumbbell. -%In both cases, silicon atom number 1 is displaced in such a way, that the bond to silicon atom number 5 vanishes. +%In both cases, silicon atom number 1 is displaced in such a way that the bond to silicon atom number 5 vanishes. %In case of~\ref{fig:defects:comb_db_04} a) the carbon atoms form a bond with a distance of 1.5 \AA, which is close to the C-C distance expected in diamond or graphit. %Both carbon atoms are highly attracted by each other resulting in large displacements and high strain energy in the surrounding. %A binding energy of 0.26 eV is observed. @@ -1275,7 +1275,7 @@ Resulting binding energies of a C$_{\text{i}}$ DB and a nearby vacancy are liste \end{figure} Figure~\ref{fig:defects:comb_db_06} shows the associated configurations. All investigated structures are preferred compared to isolated, largely separated defects. -In contrast to C$_{\text{s}}$ this is also valid for positions along \hkl[1 1 0] resulting in an entirely attractive interaction between defects of these types. +In contrast to C$_{\text{s}}$, this is also valid for positions along \hkl[1 1 0] resulting in an entirely attractive interaction between defects of these types. Even for the largest possible distance (R) achieved in the calculations of the periodic supercell a binding energy as low as \unit[-0.31]{eV} is observed. The creation of a vacancy at position 1 results in a configuration of substitutional C on a Si lattice site and no other remaining defects. The \ci{} DB atom moves to position 1 where the vacancy is created and the \si{} DB atom recaptures the DB lattice site.