X-Git-Url: https://hackdaworld.org/gitweb/?p=lectures%2Flatex.git;a=blobdiff_plain;f=posic%2Fthesis%2Fmd.tex;h=43565f211fe79c9fe87238548fa76aa709bd7ce3;hp=3253d2befee16d9578839f4ac41f86fa13bf2147;hb=06b5a10c4be0574aa9b45f7068ac8157dcb1815c;hpb=80e31ff7bd5a85d056283bc94f433c822c53fd34 diff --git a/posic/thesis/md.tex b/posic/thesis/md.tex index 3253d2b..43565f2 100644 --- a/posic/thesis/md.tex +++ b/posic/thesis/md.tex @@ -499,12 +499,20 @@ The insertion of high amounts of C into a small volume within a short period of % rt implantation + annealing Furthermore, C implanted at room temperature was found to be able to migrate towards the surface and form C-rich clusters in contrast to implantations at elevated temperatures, which form stable epitaxially aligned 3C-SiC precipitates \cite{serre95}. In simulation, low temperatures result in configurations of highly mobile \ci{} \hkl<1 0 0> DBs whereas elevated temperatures show configurations of \cs{}, which constitute an extremely stable configuration that is unlikely to migrate. +% +% added +This likewise agrees to results of IBS experiments utilizing implantation temperatures of \degc{550}, which require annealing temperatures as high as \degc{1405} for C segregation due to the stability of \cs{} \cite{reeson87}. +% Indeed, in the optimized recipe to form 3C-SiC by IBS \cite{lindner99}, elevated temperatures are used to improve the epitaxial orientation together with a low temperature implant to destroy stable SiC nanocrystals at the interface, which are unable to migrate during thermal annealing resulting in a rough surface. Furthermore, the improvement of the epitaxial orientation of the precipitate with increasing temperature in experiment perfectly conforms to the increasing occurrence of \cs{} in simulation. % -% todo add sync here starting from werner96 (Similar, implan ...) +% todo add sync here starting from strane93, werner96 ... +Moreover, implantations of an understoichiometric dose into preamorphized Si followed by an annealing step at \degc{700} result in Si$_{1-x}$C$_x$ layers with C residing on substitutional Si lattice sites \cite{strane93}. +For implantations of an understoichiometric dose into c-Si at room temperature followed by thermal annealing below and above \degc{700}, the formation of small C$_{\text{i}}$ agglomerates and SiC precipitates was observed respectively \cite{werner96}. +However, increased implantation temperatures were found to be more efficient than postannealing methods resulting in the formation of SiC precipitates for implantations at \unit[450]{$^{\circ}$C} \cite{lindner99,lindner01}. % -At elevated temperatures, implanted C is therefore expected to occupy substitutionally usual Si lattice sites right from the start. +Thus, at elevated temperatures, implanted C is expected to occupy substitutionally usual Si lattice sites right from the start. +These findings, which are outlined in more detail within the comprehensive description in chapter~\ref{chapter:summary}, are in perfect agreement with previous results of the quantum-mechanical investigations. Thus, elevated temperatures are considered to constitute a necessary condition to deviate the system from equilibrium, as it is the case in IBS. It is concluded that precipitation occurs by successive agglomeration of C$_{\text{s}}$ as already proposed by Nejim et~al.~\cite{nejim95}.