From: hackbard Date: Wed, 4 Jan 2012 18:23:40 +0000 (+0100) Subject: sec checkin (starting sic prec sims now) X-Git-Url: https://hackdaworld.org/gitweb/?a=commitdiff_plain;h=6c440bc5f807b6d785c47c2154fa91a82cb177a3;p=lectures%2Flatex.git sec checkin (starting sic prec sims now) --- diff --git a/posic/talks/defense.tex b/posic/talks/defense.tex index 00f1c5a..b7150bd 100644 --- a/posic/talks/defense.tex +++ b/posic/talks/defense.tex @@ -449,10 +449,6 @@ Synthesis of large area SiC films possible \end{slide} -%\end{document} -% temp -%\ifnum1=0 - % contents \begin{slide} @@ -714,8 +710,6 @@ r = \unit[2--4]{nm} \end{slide} -\fi - \begin{slide} \headphd @@ -1074,9 +1068,6 @@ $E_{\text{f}}=5.18\text{ eV}$\\ \end{slide} -\end{document} -\ifnum1=0 - \begin{slide} \headphd @@ -1713,6 +1704,9 @@ Contribution of entropy to structural formation\\[0.1cm] \end{slide} +% temp +\fi + \begin{slide} \headphd @@ -2152,9 +2146,6 @@ High T $\leftrightarrow$ IBS conditions far from equilibrium\\ \end{slide} -% skip high T / C conc ... only here! -\ifnum1=0 - \begin{slide} {\large\bf @@ -2221,13 +2212,11 @@ High C \& low T implants \end{slide} -% skipped high T / C conc -\fi - \begin{slide} +\headphd {\large\bf - Summary / Outlook + Summary / Conclusions } \small @@ -2292,6 +2281,11 @@ Investigation of structure \& structural evolution \ldots \item Ralf Utermann (EDV) \end{itemize} + \underline{Berlin/Brandenburg} + \begin{itemize} + \item PD Volker Eyert (Ref) + \end{itemize} + \underline{Helsinki} \begin{itemize} \item Prof. K. Nordlund (MD) @@ -2309,10 +2303,9 @@ Investigation of structure \& structural evolution \ldots \item Dr. E. Rauls (DFT + SiC) \end{itemize} - \underline{Stuttgart} \begin{center} \framebox{ -\bf Thank you for your attention / invitation! +\bf Thank you for your attention! } \end{center} @@ -2320,5 +2313,3 @@ Investigation of structure \& structural evolution \ldots \end{document} -\fi - diff --git a/posic/talks/defense.txt b/posic/talks/defense.txt index 9162a00..2df4812 100644 --- a/posic/talks/defense.txt +++ b/posic/talks/defense.txt @@ -360,13 +360,99 @@ by the classical potentials, a problem, which needs to be addressed later on. 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