\background{.40 .48 .71}{.99 .99 .99}{0.5}
\newrgbcolor{si-yellow}{.6 .6 0}
+\newrgbcolor{hb}{0.75 0.77 0.89}
+\newrgbcolor{lbb}{0.75 0.8 0.88}
+\newrgbcolor{lachs}{1.0 .93 .81}
% Groesse der einzelnen Spalten als Anteil der Gesamt-Textbreite
\renewcommand{\columnfrac}{.31}
\newcommand{\pot}{\mathcal{V}}
% header
-\vspace{-18cm}
+\vspace{-18.5cm}
\begin{header}
\centerline{{\Huge \bfseries Molecular dynamics simulation
of defect formation and precipitation}}
\begin{poster}
-%\vspace{-6cm}
+\vspace{-1cm}
\begin{pcolumn}
\begin{pbox}
\section*{Motivation}
- {\bf Reasons for understanding the 3C-SiC precipitation process}
+ {\bf Importance of the 3C-SiC precipitation process in silicon}
\begin{itemize}
- \item Significant technological progress
- in 3C-SiC wide band gap semiconductor thin film formation [1].
- \item New perspectives for processes relying upon prevention of
- precipitation, e.g. fabrication of strained pseudomorphic
- $\text{Si}_{1-y}\text{C}_y$ heterostructures [2].
+ \item SiC is a promising wide band gap material for high-temperature,
+ high-power, high-frequency semiconductor devices [1].
+ \item 3C-SiC epitaxial thin film formation on Si requires detailed
+ knowledge of SiC nucleation.
+ \item Fabrication of high carbon doped, strained pseudomorphic
+ $\text{Si}_{1-y}\text{C}_y$ layers requires suppression of
+ 3C-SiC nucleation [2].
\end{itemize}
{\tiny
[1] J. H. Edgar, J. Mater. Res. 7 (1992) 235.}\\
[2] J. W. Strane, S. R. Lee, H. J. Stein, S. T. Picraux,
J. K. Watanabe, J. W. Mayer, J. Appl. Phys. 79 (1996) 637.}
\end{pbox}
+ \vspace{-0.45cm}
\begin{pbox}
\section*{Crystalline silicon and cubic silicon carbide}
{\bf Lattice types and unit cells:}
\includegraphics[width=10cm]{sic_unit_cell.eps}
\end{minipage}
\end{pbox}
+ \vspace{-0.45cm}
\begin{pbox}
\section*{Supposed Si to 3C-SiC conversion}
{\bf Schematic of the conversion mechanism}\\\\
- \begin{minipage}{7.8cm}
- \includegraphics[width=7.7cm]{sic_prec_seq_01.eps}
+ \begin{minipage}[c]{8.8cm}
+ \includegraphics[width=8.0cm]{sic_prec_seq_01.eps}
\end{minipage}
- \hspace{0.6cm}
- \begin{minipage}{7.8cm}
- \includegraphics[width=7.7cm]{sic_prec_seq_02.eps}
+ \begin{minipage}[c]{8.8cm}
+ \includegraphics[width=8.0cm]{sic_prec_seq_02.eps}
\end{minipage}
- \hspace{0.6cm}
- \begin{minipage}{7.8cm}
- \includegraphics[width=7.7cm]{sic_prec_seq_03.eps}
+ \begin{minipage}[c]{8.1cm}
+ \includegraphics[width=8.0cm]{sic_prec_seq_03.eps}
\end{minipage}
\vspace{1cm}
\begin{enumerate}
\vspace{1cm}
{\bf Experimental observations} [3]
\begin{itemize}
- \item Minimal diameter of precipitation: 2 - 4 nm
+ \item Minimal radius of precipitates: 2 - 4 nm
\item Equal orientation of c-Si and 3C-SiC (hkl)-planes
\end{itemize}
{\tiny
[3] J. K. N. Lindner, Appl. Phys. A 77 (2003) 27.
}
\end{pbox}
+ \vspace{-0.45cm}
\begin{pbox}
\section*{Simulation details}
{\bf MD basics:}
\begin{minipage}{15cm}
{\small
\begin{pspicture}(0,0)(14,14)
- \rput(7,12.5){\rnode{init}{\psframebox[fillstyle=solid,fillcolor=green]{
+ \rput(7,12.5){\rnode{init}{\psframebox[fillstyle=solid,fillcolor=hb]{
\parbox{14cm}{
\begin{itemize}
\item Initial configuration: $9\times9\times9$ unit cells Si
\item random positions (critical distance check)
\end{itemize}
}}}}
- \rput(7,1.5){\rnode{cool}{\psframebox[fillstyle=solid,fillcolor=cyan]{
+ \rput(7,1.5){\rnode{cool}{\psframebox[fillstyle=solid,fillcolor=lbb]{
\parbox{7cm}{
Relaxation time: 2 ps
}}}}
\end{minipage}\\[1cm]
}
\begin{minipage}{17cm}
-\underline{$<100>$ dumbbell configuration}
+\underline{\flq100\frq{} dumbbell configuration}
\begin{itemize}
\item $E_f=0.47$ eV
\item Very often observed
\includegraphics[width=8cm]{c_in_si_int_001db_0.eps}
\end{minipage}\\[1cm]
\begin{center}
-\includegraphics[width=24cm]{100-c-si-db_s.eps}
+\includegraphics[width=26cm]{100-c-si-db_s.eps}\\[0.35cm]
\end{center}
{\tiny
[6] G. D. Watkins and K. L. Brower, Phys. Rev. Lett. 36 (1976) 1329.}
{\small
\begin{pspicture}(0,0)(30,13)
% nodes
- \rput(7.5,11){\rnode{init}{\psframebox[fillstyle=solid,fillcolor=green]{
+ \rput(7.5,11){\rnode{init}{\psframebox[fillstyle=solid,fillcolor=hb]{
\parbox{15cm}{
\begin{itemize}
\item Initial configuration: $31\times31\times31$ unit cells Si
\item Periodic boundary conditions
\item $T=450\, ^{\circ}\textrm{C}$, $p=0\text{ bar}$
- \item Equilibration of $E_{kin}$ and $E_{pot}$ for 600 fs
+ \item Equilibration of $E_{kin}$ and $E_{pot}$
\end{itemize}
}}}}
- \rput(7.5,5){\rnode{insert}{\psframebox[fillstyle=solid,fillcolor=red]{
+ \rput(7.5,5){\rnode{insert}{\psframebox[fillstyle=solid,fillcolor=lachs]{
\parbox{15cm}{
Insertion of 6000 carbon atoms at constant\\
- temperature into:
+ temperature into $V_1$ or $V_2$ or $V_3$:
\begin{itemize}
\item Total simulation volume $V_1$
\item Volume of minimal 3C-SiC precipitation $V_2$
\item Volume of necessary amount of Si $V_3$
\end{itemize}
}}}}
- \rput(7.5,1){\rnode{cool}{\psframebox[fillstyle=solid,fillcolor=cyan]{
+ \rput(7.5,1){\rnode{cool}{\psframebox[fillstyle=solid,fillcolor=lbb]{
\parbox{8cm}{
Cooling down to $20\, ^{\circ}\textrm{C}$
}}}}
\ncline[linewidth=0.05]{-}{in3}{in-3}
\end{pspicture}
}
-
- {\bf Results and interpretation:}\\
+ {\bf Results:}\\
Si-C and C-C pair correlation function:\\
- \includegraphics[width=24cm]{pc_si-c_c-c.eps}
+ \hspace*{1.3cm} \includegraphics[width=22cm]{pc_si-c_c-c.eps}
\begin{center}
{\tiny
{\bf Dashed vertical lines:} Further calculated C-Si distances
- in the $<100>$ C-Si dumbbell interstitial configuration}\\[0.5cm]
+ in the \flq100\frq{} C-Si dumbbell interstitial configuration}\\[0.5cm]
\end{center}
Si-Si pair correlation function:\\
- \includegraphics[width=24cm]{pc_si-si.eps}\\
+ \hspace*{1.3cm} \includegraphics[width=22cm]{pc_si-si.eps}\\
+ {\bf Interpretation:}
{\small
\begin{itemize}
\item C-C peak at 0.15 nm similar to next neighbour distance of graphite
or diamond\\
$\Rightarrow$ Formation of strong C-C bonds
(almost only for high C concentrations)
+ \item Si-C peak at 0.19 nm similar to next neighbour distance in 3C-SiC
\item C-C peak at 0.31 nm equals C-C distance in 3C-SiC\\
(due to concatenated, differently oriented
- $<100>$ dumbbell interstitials)
- \item Si-Si shows non-zero g(r) values around 0.31 nm
- and decrease at regular distances\\
+ \flq100\frq{} dumbbell interstitials)
+ \item Si-Si shows non-zero g(r) values around 0.31 nm like in 3C-SiC\\
+ and a decrease at regular distances\\
(no clear peak,
interval of enhanced g(r) corresponds to C-C peak width)
- \item Si-C peak at 0.19 nm similar to next neighbour distance in 3C-SiC
- \item Low C concentration (i.e. $V_1$): The $<100>$ dumbbell configuration
+ \item Low C concentration (i.e. $V_1$):
+ The \flq100\frq{} dumbbell configuration
\begin{itemize}
\item is identified to stretch the Si-Si next neighbour distance
to 0.3 nm
\item is identified to contribute to the Si-C peak at 0.19 nm
\item explains further C-Si peaks (dashed vertical lines)
\end{itemize}
+ $\Rightarrow$ C atoms are first elements arranged at distances
+ expected for 3C-SiC\\
+ $\Rightarrow$ C atoms pull the Si atoms into the right
+ configuration at a later stage
\item High C concentration (i.e. $V_2$ and $V_3$):
\begin{itemize}
\item High amount of damage introduced into the system
\item Short range order observed but almost no long range order
\end{itemize}
+ $\Rightarrow$ Start of amorphous SiC-like phase formation\\
+ $\Rightarrow$ Higher temperatures required for proper SiC formation
\end{itemize}
}
\end{pbox}
+ \vspace{-2cm}
\begin{pbox}
- \section*{Conclusions}
+ \section*{Conclusion}
\begin{itemize}
- \item there should be
- \item 3 conclusions
- \item at least!
+ \item \flq100\frq{} C-Si dumbbell interstitial configuration is observed
+ to be the energetically most favorable configuration
+ \item For low C concentrations C atoms introduced as differently
+ oriented C-Si dumbbells in c-Si are properly arranged
+ for 3C-SiC formation
+ \item For high C concentrations an amorphous SiC-like phase is observed
+ which suggests higher temperature simulation runs for proper
+ 3C-SiC formation
\end{itemize}
\end{pbox}
+ \vspace{-2cm}
+ \begin{pbox}
+ One of us (F. Z.) wants to acknowledge financial support by the\\
+ {\bf Bayerische Forschungsstiftung} (DPA-61/05).
+ \end{pbox}
\end{pcolumn}
\end{poster}
projects / lectures / latex.git / blobdiff