% fabrication
-\ifnum1=0
-\begin{slide}
-
-\headphd
- {\large\bf
- Fabrication of silicon carbide
- }
-
- \small
-
- \vspace{2pt}
-
-\begin{center}
- {\color{gray}
- \emph{Silicon carbide --- Born from the stars, perfected on earth.}
- }
-\end{center}
-
-\vspace{2pt}
-
-SiC thin films by MBE \& CVD
-\begin{itemize}
- \item Much progress achieved in homo/heteroepitaxial SiC thin film growth
- \item \underline{Commercially available} semiconductor power devices based on
- \underline{\foreignlanguage{greek}{a}-SiC}
- \item Production of favored \underline{3C-SiC} material
- \underline{less advanced}
- \item Quality and size not yet sufficient
-\end{itemize}
-\begin{picture}(0,0)(-310,-20)
- \includegraphics[width=2.0cm]{cree.eps}
-\end{picture}
-
-\vspace{-0.5cm}
-
-%\begin{center}
-%\color{red}
-%\framebox{
-%{\footnotesize\color{black}
-% Mismatch in \underline{thermal expansion coeefficient}
-% and \underline{lattice parameter} w.r.t. substrate
-%}
-%}
-%\end{center}
-
-\vspace{0.1cm}
-
-{\bf Alternative approach}\\
-Ion beam synthesis (IBS) of burried 3C-SiC layers in Si\hkl(1 0 0)
-
-\vspace{0.1cm}
-
-\scriptsize
-
-\framebox{
-\begin{minipage}{3.15cm}
- \begin{center}
-\includegraphics[width=3cm]{imp.eps}\\
- {\tiny
- Carbon implantation
- }
- \end{center}
-\end{minipage}
-\begin{minipage}{3.15cm}
- \begin{center}
-\includegraphics[width=3cm]{annealing.eps}\\
- {\tiny
- Postannealing at $>$ \degc{1200}
- }
- \end{center}
-\end{minipage}
-}
-\begin{minipage}{5.5cm}
- \includegraphics[width=5.8cm]{ibs_3c-sic.eps}\\[-0.2cm]
- \begin{center}
- {\tiny
- XTEM: single crystalline 3C-SiC in Si\hkl(1 0 0)
- }
- \end{center}
-\end{minipage}
-
-%\begin{minipage}{5.5cm}
-%\begin{center}
-%{\footnotesize
-%No surface bending effects\\
-%High areal homogenity\\[0.1cm]
-%$\Downarrow$\\[0.1cm]
-%Synthesis of large area SiC films possible
-%}
-%\end{center}
-%\end{minipage}
-
-\end{slide}
-\fi
-
\begin{slide}
\headphd
\end{center}
\end{minipage}
\begin{minipage}{5cm}
+\begin{center}
\begin{pspicture}(0,0)(0,0)
\rnode{box}{
\psframebox[fillstyle=solid,fillcolor=white,linecolor=blue,linestyle=solid]{
-\begin{minipage}{5.3cm}
+\begin{minipage}{3.3cm}
\begin{center}
{\color{blue}
3C-SiC precipitation\\
not yet fully understood
}
\end{center}
- \vspace*{0.1cm}
- \renewcommand\labelitemi{$\Rightarrow$}
- Details of the SiC precipitation
- \begin{itemize}
- \item significant technological progress\\
- in SiC thin film formation
- \item perspectives for processes relying\\
- upon prevention of SiC precipitation
- \end{itemize}
+% \vspace*{0.1cm}
+% \renewcommand\labelitemi{$\Rightarrow$}
+% Details of the SiC precipitation
+% \begin{itemize}
+% \item significant technological progress\\
+% in SiC thin film formation
+% \item perspectives for processes relying\\
+% upon prevention of SiC precipitation
+% \end{itemize}
\end{minipage}
}}
-\rput(-6.8,5.5){\pnode{h0}}
-\rput(-3.0,5.5){\pnode{h1}}
+\rput(-5.3,5.5){\pnode{h0}}
+\rput(-1.95,5.5){\pnode{h1}}
\ncline[linecolor=blue]{-}{h0}{h1}
\ncline[linecolor=blue]{->}{h1}{box}
\end{pspicture}
+\end{center}
\end{minipage}
\end{slide}
\end{itemize}
$\Rightarrow$ mobile {\color{red}\ci} opposed to
stable {\color{blue}\cs{}} configurations
-\item Strained silicon \& Si$_{1-y}$C$_y$ heterostructures
+\item Strained Si$_{1-y}$C$_y$/Si heterostructures
{\tiny\color{gray}/Strane~et~al./Guedj~et~al./}
\begin{itemize}
- \item Initial {\color{blue}coherent} SiC precipitates (tensile strain)
- \item Incoherent SiC (strain relaxation)
+ \item Initial {\color{blue}coherent} SiC structures (tensile strain)
+ \item Incoherent SiC nanocrystals (strain relaxation)
\end{itemize}
\end{itemize}
\vspace{0.1cm}
\end{minipage}
\end{minipage}
-\vspace{0.2cm}
+\vspace{0.3cm}
-\begin{minipage}[b]{6cm}
+\begin{minipage}[t]{6cm}
{\bf Defect formation energy}\\
\framebox{
-$E_{\text{f}}=E-\sum_i N_i\mu_i$}\\[0.1cm]
-Particle reservoir: Si \& SiC\\[0.2cm]
+$E_{\text{f}}=E-\sum_i N_i\mu_i$}\\[0.5cm]
+%Particle reservoir: Si \& SiC\\[0.2cm]
{\bf Binding energy}\\
\framebox{
$
$E_{\text{b}}<0$: energetically favorable configuration\\
$E_{\text{b}}\rightarrow 0$: non-interacting, isolated defects\\
\end{minipage}
-\begin{minipage}[b]{6cm}
+\begin{minipage}[t]{6cm}
+\vspace{1.4cm}
{\bf Migration barrier}
\footnotesize
\begin{itemize}
\begin{itemize}
\item Bond-centered configuration unstable\\
$\rightarrow$ \ci{} \hkl<1 1 0> dumbbell
- \item Minima of the \hkl[0 0 -1] to \hkl[0 -1 0] transition\\
+ \item Minimum of the \hkl[0 0 -1] to \hkl[0 -1 0] transition\\
$\rightarrow$ \ci{} \hkl<1 1 0> DB
\end{itemize}
\vspace{0.1cm}
\begin{minipage}{6.1cm}
\scriptsize
\underline{Low C concentration --- {\color{red}$V_1$}}\\[0.1cm]
-\hkl<1 0 0> C-Si dumbbell dominated structure
+\ci{} \hkl<1 0 0> dumbbell dominated structure
\begin{itemize}
\item Si-C bumbs around \unit[0.19]{nm}
\item C-C peak at \unit[0.31]{nm} (expected in 3C-SiC):\\
\begin{minipage}{6cm}
\centering
Formation of \ci{} dumbbells\\
-C atoms in proper 3C-SiC distance first
+C atoms separated as expected in 3C-SiC
\end{minipage}
}}
\end{pspicture}\\[0.1cm]
\begin{minipage}{6.1cm}
\scriptsize
\underline{Low C concentration --- {\color{red}$V_1$}}\\[0.1cm]
-\hkl<1 0 0> C-Si dumbbell dominated structure
+\ci{} \hkl<1 0 0> dumbbell dominated structure
\begin{itemize}
\item Si-C bumbs around \unit[0.19]{nm}
\item C-C peak at \unit[0.31]{nm} (expected in 3C-SiC):\\
\begin{minipage}{6cm}
\centering
Formation of \ci{} dumbbells\\
-C atoms in proper 3C-SiC distance first
+C atoms separated as expected in 3C-SiC
\end{minipage}
}}
\end{pspicture}\\[0.1cm]
\vspace{0.2cm}
{\bf Time scale problem of MD}\\[0.2cm]
-Precise integration \& thermodynamic sampling\\
+Minimize integration error \& precise thermodynamic sampling\\
$\Rightarrow$ $\Delta t \ll \left( \max{\omega} \right)^{-1}$,
$\omega$: vibrational mode\\
$\Rightarrow$ {\color{red}\underline{Slow}} phase space propagation\\[0.2cm]
{\bf Limitations related to the short range potential}\\[0.2cm]
Cut-off function limits interaction to next neighbours\\
-$\Rightarrow$ Overestimated unphysical high forces of next neighbours
- (factor: 2.4--3.4)
+$\Rightarrow$ Overestimated diffusion barrier (factor: 2.4--3.4)
\vspace{1.4cm}
\underline{Si-C bonds:}
\begin{itemize}
\item Vanishing cut-off artifact (above $1650\,^{\circ}\mathrm{C}$)
- \item Structural change: C-Si \hkl<1 0 0> $\rightarrow$ C$_{\text{sub}}$
+ \item Structural change: \ci{} \hkl<1 0 0> DB $\rightarrow$
+ {\color{blue}\cs{}}
\end{itemize}
\underline{Si-Si bonds:}
{\color{blue}Si-C$_{\text{sub}}$-Si} along \hkl<1 1 0>
\underline{C-C bonds:}
\begin{itemize}
\item C-C next neighbour pairs reduced (mandatory)
- \item Peak at 0.3 nm slightly shifted
- \begin{itemize}
- \item C-Si \hkl<1 0 0> combinations (dashed arrows)\\
- $\rightarrow$ C-Si \hkl<1 0 0> \& C$_{\text{sub}}$
- combinations (|)\\
- $\rightarrow$ pure {\color{blue}C$_{\text{sub}}$ combinations}
- ($\downarrow$)
- \item Range [|-$\downarrow$]:
- {\color{blue}C$_{\text{sub}}$ \& C$_{\text{sub}}$
- with nearby Si$_{\text{I}}$}
- \end{itemize}
+ \item Peak at 0.3 nm slightly shifted\\[0.05cm]
+ $\searrow$ \ci{} combinations (dashed arrows)\\
+ $\nearrow$ \ci{} \hkl<1 0 0> \& {\color{blue}\cs{} combinations} (|)\\
+ $\nearrow$ \ci{} pure \cs{} combinations ($\downarrow$)\\[0.05cm]
+ Range [|-$\downarrow$]: {\color{blue}\cs{} \& \cs{} with nearby \si}
\end{itemize}
\end{minipage}
\underline{Si-C bonds:}
\begin{itemize}
\item Vanishing cut-off artifact (above $1650\,^{\circ}\mathrm{C}$)
- \item Structural change: C-Si \hkl<1 0 0> $\rightarrow$ C$_{\text{sub}}$
+ \item Structural change: \ci{} \hkl<1 0 0> DB $\rightarrow$
+ {\color{blue}\cs{}}
\end{itemize}
\underline{Si-Si bonds:}
{\color{blue}Si-C$_{\text{sub}}$-Si} along \hkl<1 1 0>
\begin{itemize}
\item C-C next neighbour pairs reduced (mandatory)
\item Peak at 0.3 nm slightly shifted
- \begin{itemize}
- \item C-Si \hkl<1 0 0> combinations (dashed arrows)\\
- $\rightarrow$ C-Si \hkl<1 0 0> \& C$_{\text{sub}}$
- combinations (|)\\
- $\rightarrow$ pure {\color{blue}C$_{\text{sub}}$ combinations}
- ($\downarrow$)
- \item Range [|-$\downarrow$]:
- {\color{blue}C$_{\text{sub}}$ \& C$_{\text{sub}}$
- with nearby Si$_{\text{I}}$}
- \end{itemize}
+ \item Peak at 0.3 nm slightly shifted\\[0.05cm]
+ $\searrow$ \ci{} combinations (dashed arrows)\\
+ $\nearrow$ \ci{} \hkl<1 0 0> \& {\color{blue}\cs{} combinations} (|)\\
+ $\nearrow$ \ci{} pure \cs{} combinations ($\downarrow$)\\[0.05cm]
+ Range [|-$\downarrow$]: {\color{blue}\cs{} \& \cs{} with nearby \si}
\end{itemize}
\end{minipage}
{\Huge$\lightning$} {\color{red}\ci{}} --- vs --- {\color{blue}\cs{}} {\Huge$\lightning$}\\
\end{center}
\begin{itemize}
-\item Stretched coherent SiC structures\\
-$\Rightarrow$ Precipitation process involves {\color{blue}\cs}
-\item Role of \si{}
+\item Stretched coherent SiC structures directly observed
+\begin{center}
+\psframebox[linecolor=blue,linewidth=0.05cm]{
+\begin{minipage}{7cm}
+\centering
+\cs{} extensively involved in the precipitation mechanism\\
+\end{minipage}
+}
+\end{center}
+\item Emission of \si{} serves several needs:
\begin{itemize}
\item Vehicle to rearrange \cs --- [\cs{} \& \si{} $\leftrightarrow$ \ci]
\item Building block for surrounding Si host \& further SiC
\psframebox[linecolor=blue,linewidth=0.05cm]{
\begin{minipage}{7cm}
\centering
-Precipitation mechanism involving \cs\\
High T $\leftrightarrow$ IBS conditions far from equilibrium\\
\end{minipage}
}
% skip high c conc
\fi
-% for preparation
-%\fi
-
\begin{slide}
\headphd
\item Identified \ci{} migration path
\item EA drastically overestimates the diffusion barrier
\end{itemize}
- \item Combinations of defects
+ \item Combinations of defects (DFT)
\begin{itemize}
\item Agglomeration of point defects energetically favorable
\item C$_{\text{sub}}$ favored conditions (conceivable in IBS)
\item Low T $\rightarrow$ C-Si \hkl<1 0 0> dumbbell dominated structure
\item High T $\rightarrow$ C$_{\text{sub}}$ dominated structure
\item High T necessary to simulate IBS conditions (far from equilibrium)
- \item Increased participation of \cs{} in the precipitation process
+ \item \cs{} involved in the precipitation process at elevated temperatures
\item \si{}: vehicle to form \cs{} \& supply of Si \& stress compensation
(stretched SiC, interface)
\end{itemize}
\begin{center}
{\color{blue}\bf
-\framebox{Precipitation by successive agglomeration of \cs{}}
+\framebox{IBS: 3C-SiC precipitation occurs by successive agglomeration of \cs{}}
}
\end{center}
Thanks to \ldots
+\begin{minipage}[t]{6cm}
\underline{Augsburg}
\begin{itemize}
\item Prof. B. Stritzker
\item Ralf Utermann
+ \item EP \RM{4}
\end{itemize}
\underline{Helsinki}
\item Prof. G. Schmidt
\item Dr. E. Rauls
\end{itemize}
+\end{minipage}
+\begin{minipage}[t]{6cm}
+\underline{Referees}
+ \begin{itemize}
+ \item PD V. Eyert
+ \item Prof. F. Haider
+ \end{itemize}
+\end{minipage}
-\vspace{ 0.2cm}
-
+\vspace{0.5cm}
\begin{center}
\framebox{
-\normalsize\bf Thank you for your attention!
+\Large\bf Thank you for your attention!
}
\end{center}
\end{slide}
+
+
+
+
+
+
\begin{slide}
\headphd
projects / lectures / latex.git / blobdiff