\end{pspicture}
-\begin{picture}(0,0)(-10,68)
+\begin{picture}(0,0)(-3,68)
\includegraphics[width=2.6cm]{wide_band_gap.eps}
\end{picture}
-\begin{picture}(0,0)(-295,-165)
-\includegraphics[width=3cm]{sic_led.eps}
+\begin{picture}(0,0)(-285,-162)
+\includegraphics[width=3.38cm]{sic_led.eps}
\end{picture}
-\begin{picture}(0,0)(-215,-165)
-\includegraphics[width=2.5cm]{6h-sic_3c-sic.eps}
+\begin{picture}(0,0)(-195,-162)
+\includegraphics[width=2.8cm]{6h-sic_3c-sic.eps}
\end{picture}
\begin{picture}(0,0)(-313,65)
\includegraphics[width=2.2cm]{infineon_schottky.eps}
\begin{picture}(0,0)(-220,65)
\includegraphics[width=2.9cm]{sic_wechselrichter_ise.eps}
\end{picture}
+\begin{picture}(0,0)(0,-160)
+\includegraphics[width=3.0cm]{sic_proton.eps}
+\end{picture}
+\begin{picture}(0,0)(-60,65)
+\includegraphics[width=3.4cm]{sic_switch.eps}
+\end{picture}
\end{slide}
}
\end{minipage}
\end{picture}
+ \begin{picture}(0,0)(-230,-35)
+ \framebox{
+ {\footnotesize\color{blue}\bf Hex: micropipes along c-axis}
+ }
+ \end{picture}
+ \begin{picture}(0,0)(-230,-10)
+ \framebox{
+ \begin{minipage}{3cm}
+ {\footnotesize\color{blue}\bf 3C-SiC fabrication\\
+ less advanced}
+ \end{minipage}
+ }
+ \end{picture}
\end{slide}
\psellipse[linecolor=blue](11.5,5.8)(0.3,0.5)
\rput{-20}{\psellipse[linecolor=blue](3.3,8.1)(0.3,0.5)}
\psline[linewidth=4pt]{->}(4.0,2)(4.5,2)
+\rput(12.7,0.3){\rnode{init}{\psframebox[fillstyle=solid,fillcolor=hb]{
+ $4a_{\text{Si}}=5a_{\text{SiC}}$
+ }}}
+\rput(12.2,8){\rnode{init}{\psframebox[fillstyle=solid,fillcolor=hb]{
+\hkl(h k l) planes match
+ }}}
\end{pspicture}
-
+
\end{slide}
\begin{slide}
\[
\rightarrow
\text{Fourier series: } \Phi_i=\sum_{|G+k|<G_{\text{cut}}} c_j^i \phi_j(r), \quad E_{\text{cut}}=\frac{\hbar^2}{2m}G^2_{\text{cut}}
+\qquad ({\color{blue}300\text{ eV}})
\]
- \item \underline{$k$-point sampling} - $\Gamma$-point only calculations
+ \item \underline{Brillouin zone sampling} -
+ {\color{blue}$\Gamma$-point only} calculations
\item \underline{Pseudo potential}
- consider only the valence electrons
\item \underline{Code} - VASP 4.6
\item Structural optimization: Conjugate gradient method
\end{itemize}
+\begin{pspicture}(0,0)(0,0)
+\psellipse[linecolor=blue](1.5,6.75)(0.5,0.3)
+\end{pspicture}
+
\end{slide}
\begin{slide}
\begin{minipage}{5cm}
Introduced C (defects)\\
$\rightarrow$ reduction of transition point\\
-$\rightarrow$ melting even at $T_{\text{m}}$
+$\rightarrow$ melting already at $T_{\text{m}}$
\end{minipage}
}
Long time scale simulations at maximum temperature
}
- \small
-
-\vspace{1cm}
+\small
+\vspace{0.1cm}
+
\underline{Differences}
\begin{itemize}
- \item Cubic volume $\Rightarrow$ spherical volume
- \item Amount of C atoms: 6000 $\rightarrow$ 5500
\item Temperature set to $0.95 \cdot T_{\text{m}}$
+ \item Cubic insertion volume $\Rightarrow$ spherical insertion volume
+ \item Amount of C atoms: 6000 $\rightarrow$ 5500
+ $\Leftrightarrow r_{\text{prec}}=0.3\text{ nm}$
\item Simulation volume: 21 unit cells of c-Si in each direction
\end{itemize}
-\vspace{1cm}
+\footnotesize
+
+\vspace{0.3cm}
+\begin{minipage}[t]{4.5cm}
\begin{center}
- {\bf
-Simulations in progress! :)\\
- }
-... show evolution of radial distribution in ns timesteps ...
+\underline{Low C concentration, Si-C}
+\includegraphics[width=4.5cm]{c_in_si_95_v1_si-c.ps}\\
+Sharper peaks!
\end{center}
+\end{minipage}
+\begin{minipage}[t]{4.5cm}
+\begin{center}
+\underline{Low C concentration, C-C}
+\includegraphics[width=4.5cm]{c_in_si_95_v1_c-c.ps}\\
+Sharper peaks!\\
+No C agglomeration!
+\end{center}
+\end{minipage}
+\begin{minipage}[t]{4cm}
+\begin{center}
+\underline{High C concentration}
+\includegraphics[width=4.5cm]{c_in_si_95_v2.ps}\\
+No significant changes
+\end{center}
+\end{minipage}
-\vspace{4cm}
+\begin{center}
+\framebox{
+Long time scales and high temperatures most probably not sufficient enough!
+}
+\end{center}
\end{slide}
\item Spherical topotactically aligned precipitate\\
$r=3.0\text{ nm}$ $\Leftrightarrow$ $\approx$ 5500 C atoms
\item Create c-Si but skipped inside sphere of radius $x$
- \item Create 3C-SiC inside sphere of radius $x$ and lattice constant $y$
+ \item Create 3C-SiC inside sphere of radius $x$\\
+ and lattice constant $y$
\item Strong coupling to heat bath ($T=20\,^{\circ}\mathrm{C}$)
\end{itemize}
\end{minipage}
\vspace{0.3cm}
\begin{minipage}{6.2cm}
-\includegraphics[width=6cm,draft=false]{pc_0.ps}
+\includegraphics[width=6cm]{pc_0.ps}
\end{minipage}
\begin{minipage}{6.8cm}
\underline{Results}
\item Slight increase of c-Si lattice constant!
\item C-C peaks (imply same distanced Si-Si peaks)
\begin{itemize}
- \item New peak at 0.307 nm: NN in 3C-SiC
+ \item New peak at 0.307 nm: 2$^{\text{nd}}$ NN in 3C-SiC
\item Bumps ({\color{green}$\downarrow$}):
4$^{\text{th}}$ and 6$^{\text{th}}$ NN
\end{itemize}
\item 3C-SiC lattice constant: 4.34 \AA (bulk: 4.36 \AA)\\
$\rightarrow$ compressed precipitate
\item Interface tension:\\
- 20.15 eV/nm$^2$ or $3.23 \times 10^{-4}$ J/cm$^2$
+ 20.15 eV/nm$^2$ or $3.23 \times 10^{-4}$ J/cm$^2$\\
+ (literature: $2 - 8 \times 10^{-4}$ J/cm$^2$)
+\end{itemize}
+\end{minipage}
+
+\end{slide}
+
+\begin{slide}
+
+ {\large\bf
+ Investigation of a silicon carbide precipitate in silicon
+ }
+
+ \footnotesize
+
+\begin{minipage}{7cm}
+\underline{Appended annealing steps}
+\begin{itemize}
+ \item artificially constructed interface\\
+ $\rightarrow$ allow for rearrangement of interface atoms
+ \item check SiC stability
+\end{itemize}
+\underline{Temperature schedule}
+\begin{itemize}
+ \item rapidly heat up structure up to $2050\,^{\circ}\mathrm{C}$\\
+ (75 K/ps)
+ \item slow heating up to $1.2\cdot T_{\text{m}}=2940\text{ K}$
+ by 1 K/ps\\
+ $\rightarrow$ melting at around 2840 K
+ (\href{../video/sic_prec_120.avi}{$\rhd$})
+ \item cooling down structure at 100 \% $T_{\text{m}}$ (1 K/ps)\\
+ $\rightarrow$ no energetically more favorable struture
\end{itemize}
\end{minipage}
+\begin{minipage}{6cm}
+\includegraphics[width=6.7cm]{fe_and_t_sic.ps}
+\end{minipage}
+
+\begin{minipage}{4cm}
+\includegraphics[width=4cm]{sic_prec/melt_01.eps}
+\end{minipage}
+\begin{minipage}{0.4cm}
+$\rightarrow$
+\end{minipage}
+\begin{minipage}{4cm}
+\includegraphics[width=4cm]{sic_prec/melt_02.eps}
+\end{minipage}
+\begin{minipage}{0.4cm}
+$\rightarrow$
+\end{minipage}
+\begin{minipage}{4cm}
+\includegraphics[width=4cm]{sic_prec/melt_03.eps}
+\end{minipage}
\end{slide}
Summary / Conclusion / Outlook
}
- \small
+ \scriptsize
-
+\vspace{0.1cm}
+
+\framebox{
+\begin{minipage}{12.9cm}
+ \underline{Defects}
+ \begin{itemize}
+ \item Summary \& conclusion
+ \begin{itemize}
+ \item Point defects excellently / fairly well described
+ by QM / classical potential simulations
+ \item Identified migration path explaining
+ diffusion and reorientation experiments
+ \item Agglomeration of point defects energetically favorable
+ \item C$_{\text{sub}}$ favored conditions (conceivable in IBS)
+ \end{itemize}
+ \item Todo
+ \begin{itemize}
+ \item Discussions concerning interpretation of QM results (Paderborn)
+ \item Compare migration barrier of
+ \hkl<1 1 0> Si and C-Si \hkl<1 0 0> dumbbell
+ \item Combination: Vacancy \& \hkl<1 1 0> Si self-interstitial \&
+ C-Si \hkl<1 0 0> dumbbell (IBS)
+ \end{itemize}
+ \end{itemize}
+\end{minipage}
+}
+
+\vspace{0.2cm}
+
+\framebox{
+\begin{minipage}[t]{6.2cm}
+ \underline{Pecipitation simulations}
+ \begin{itemize}
+ \item Summary \& conclusion
+ \begin{itemize}
+ \item Low T
+ $\rightarrow$ C-Si \hkl<1 0 0> dumbbell\\
+ dominated structure
+ \item High T $\rightarrow$ C$_{\text{sub}}$ dominated structure
+ \item High C concentration\\
+ $\rightarrow$ amorphous SiC like phase
+ \end{itemize}
+ \item Todo
+ \begin{itemize}
+ \item Accelerated method: self-guided MD
+ \item Activation relaxation technique
+ \item Constrainted transition path
+ \end{itemize}
+ \end{itemize}
+\end{minipage}
+}
+\framebox{
+\begin{minipage}[t]{6.2cm}
+ \underline{Constructed 3C-SiC precipitate}
+ \begin{itemize}
+ \item Summary \& conclusion
+ \begin{itemize}
+ \item Small / stable / compressed 3C-SiC\\
+ precipitate in slightly stretched\\
+ c-Si matrix
+ \item Interface tension matches experiemnts
+ \end{itemize}
+ \item Todo
+ \begin{itemize}
+ \item Try to improve interface
+ \item Precipitates of different size
+ \end{itemize}
+ \end{itemize}
+\end{minipage}
+}
+
+ \small
\end{slide}
Acknowledgements
}
+ \vspace{0.1cm}
+
\small
+ Thanks to \ldots
+
+ \underline{Augsburg}
+ \begin{itemize}
+ \item Prof. B. Stritzker (accepting a simulator at EP \RM{4})
+ \item Ralf Utermann (EDV)
+ \end{itemize}
+ \underline{Helsinki}
+ \begin{itemize}
+ \item Prof. K. Nordlund (MD)
+ \end{itemize}
+
+ \underline{Munich}
+ \begin{itemize}
+ \item Bayerische Forschungsstiftung (financial support)
+ \end{itemize}
+
+ \underline{Paderborn}
+ \begin{itemize}
+ \item Prof. J. Lindner (SiC)
+ \item Prof. G. Schmidt (DFT + financial support)
+ \item Dr. E. Rauls (DFT + SiC)
+ \end{itemize}
+
+\vspace{0.2cm}
+
+\begin{center}
+\framebox{
+\bf Thank you for your attention!
+}
+\end{center}
\end{slide}
projects / lectures / latex.git / blobdiff