From: hackbard Date: Wed, 18 Aug 2010 19:55:16 +0000 (+0200) Subject: c_i - c_s stuff X-Git-Url: https://hackdaworld.org/gitweb/?p=lectures%2Flatex.git;a=commitdiff_plain;h=392cc7a1756e8925d85082c6d605b840310929f4 c_i - c_s stuff --- diff --git a/posic/publications/defect_combos.tex b/posic/publications/defect_combos.tex index b863fc9..54d5087 100644 --- a/posic/publications/defect_combos.tex +++ b/posic/publications/defect_combos.tex @@ -47,7 +47,7 @@ However, the process of the formation of SiC precipitates in Si during C implant Based on experimental studies\cite{werner96,werner97,eichhorn99,lindner99_2,koegler03} it is assumed that incorporated C atoms form C-Si dimers (dumbbells) on regular Si lattice sites. The highly mobile C interstitials agglomerate into large clusters followed by the formation of incoherent 3C-SiC nanocrystallites once a critical size of the cluster is reached. In contrast, investigations of the precipitation in strained Si$_{1-y}$C$_y$/Si heterostructures formed by molecular beam epitaxy (MBE)\cite{strane94,guedj98} suggest an initial coherent clustering of substitutional instead of interstitial C followed by a loss of coherency once the increasing strain energy surpasses the interfacial energy of an incoherent 3C-SiC precipitate in c-Si. -These two different mechanisms of precipitation might be determined by the respective method of fabrication. +These two different mechanisms of precipitation might be attributed to the respective method of fabrication. However, in another IBS study Nejim et al. propose a topotactic transformation remaining structure and orientation likewise based on the formation of substitutional C and a concurrent reaction of the excess Si self-interstitials with further implanted C atoms in the initial state\cite{nejim95}. Solving this controversy and understanding the effective underlying processes will enable significant technological progress in 3C-SiC thin film formation driving the superior polytype for potential applications in high-performance electronic device production\cite{wesch96}. @@ -217,7 +217,7 @@ Low barriers do only exist from energetically less favorable configurations, e.g Starting from this configuration, an activation energy of only \unit[1.2]{eV} is necessary for the transition into the ground state configuration. The corresponding migration energies and atomic configurations are displayed in Fig.~\ref{fig:036-239}. \begin{figure} -\includegraphics[width=\columnwidth]{036-239.eps} +\includegraphics[width=\columnwidth]{036-239.ps} \caption{Migration barrier and structures of the transition of a C$_{\text{i}}$ \hkl[-1 0 0] DB at position 2 (left) into a C$_{\text{i}}$ \hkl[0 -1 0] DB at position 1 (right). An activation energy of \unit[1.2]{eV} is observed.} \label{fig:036-239} \end{figure} @@ -242,7 +242,7 @@ Secondly, a migration path with a barrier as low as \unit[?.?]{eV} exists starti The migration barrier and correpsonding structures are shown in Fig.~\ref{fig:188-225}. % 188 - 225 transition in progress \begin{figure} -\includegraphics[width=\columnwidth]{188-225.eps} +\includegraphics[width=\columnwidth]{188-225.ps} \caption{Migration barrier and structures of the transition of a C$_{\text{i}}$ \hkl[0 -1 0] DB at position 5 (left) into a C$_{\text{i}}$ \hkl[1 0 0] DB at position 1 (right). An activation energy of \unit[?.?]{eV} is observed.} \label{fig:188-225} \end{figure} @@ -309,6 +309,11 @@ Present results show a difference in energy of states A and B, which exactly mat %Figure~\ref{fig:AB} displays the two configurations and migration barrier for the transition among the two states. % a b +\begin{figure} +\includegraphics[width=\columnwidth]{026-128.ps} +\caption{Migration barrier and structures of the transition of the initial C$_{\text{i}}$ \hkl[0 0 -1] DB and C$_{\text{s}}$ at position 1 (left) into a C-C \hkl[1 0 0] DB occupying the lattice site at position 1 (right). An activation energy of \unit[0.1]{eV} is observed.} +\label{fig:026-128} +\end{figure} Configuration a is similar to configuration A except that the C$_{\text{s}}$ at position 1 is facing the C DB atom as a next neighbor resulting in the formation of a strong C-C bond and a much more noticeable perturbation of the DB structure. Nevertheless, the C and Si DB atoms remain threefold coordinated. Although the C-C bond exhibiting a distance of \unit[0.15]{nm} close to the distance expected in diamond or graphite should lead to a huge gain in energy, a repulsive interaction with a binding energy of \unit[0.26]{eV} is observed due to compressive strain of the Si DB atom and its top neighbors (\unit[0.230]{nm}/\unit[0.236]{nm}) along with additional tensile strain of the C$_{\text{s}}$ and its three neighboring Si atoms (\unit[0.198-0.209]{nm}/\unit[0.189]{nm}). @@ -322,7 +327,7 @@ Spin polarization for C-C Int resulting spin up electrons located as in the case % mattoni: A favored by 0.2 eV - NO! (again, missing spin polarization?) % mig a-b -% 2 more migs: 051 -> 128 and 026! forgot why ... +% 2 more migs: 051 -> 128 and 026! forgot why ... probably it's about probability of C clustering \subsection{C$_{\text{i}}$ next to V}