\vspace{16pt}
- {\LARGE\bf
- Atomistic simulation study\\[0.2cm]
- on silicon carbide precipitation\\[0.2cm]
- in silicon
+ {\Large\bf
+ \hrule
+ \vspace{5pt}
+ Atomistic simulation study on silicon carbide\\[0.2cm]
+ precipitation in silicon\\
+ \vspace{10pt}
+ \hrule
}
- \vspace{48pt}
+ \vspace{60pt}
\textsc{Frank Zirkelbach}
- \vspace{48pt}
+ \vspace{60pt}
Defense of doctor's thesis
\vspace{08pt}
- Augsburg, 10. Jan. 2012
+ Augsburg, 10.01.2012
\end{center}
\end{slide}
% no vertical centering
\centerslidesfalse
+% skip for preparation
+\ifnum1=0
+
% intro
% motivation / properties / applications of silicon carbide
\begin{slide}
{\large\bf
- Polytypes of SiC\\[0.4cm]
+ Polytypes of SiC\\[0.6cm]
}
+\vspace{0.6cm}
+
\includegraphics[width=3.8cm]{cubic_hex.eps}\\
\begin{minipage}{1.9cm}
{\tiny cubic (twist)}
\end{slide}
+\fi
+
% fabrication
\begin{slide}
\begin{picture}(0,0)(-310,-20)
\includegraphics[width=2.0cm]{cree.eps}
\end{picture}
+{\color{red}\scriptsize Mismatch in thermal expansion coeefficient
+ and lattice paramater}
\vspace{-0.2cm}
-Alternative approach:
+{\bf Alternative approach}\\
Ion beam synthesis (IBS) of burried 3C-SiC layers in Si\hkl(1 0 0)
-\vspace{0.2cm}
+\vspace{0.1cm}
\scriptsize
\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}
-
-\end{slide}
-
-% contents
-
-\begin{slide}
-
-\headphd
-{\large\bf
- Outline
+\begin{center}
+{\small
+No surface bending effects\\
+$\Rightarrow$ Synthesis of large area SiC films possible
}
-
- \begin{itemize}
- \item Supposed precipitation mechanism of SiC in Si
- \item Utilized simulation techniques
- \begin{itemize}
- \item Molecular dynamics (MD) simulations
- \item Density functional theory (DFT) calculations
- \end{itemize}
- \item C and Si self-interstitial point defects in silicon
- \item Silicon carbide precipitation simulations
- \item Summary / Conclusion / Outlook
- \end{itemize}
+\end{center}
+\end{minipage}
\end{slide}
\headphd
{\large\bf
- Formation of epitaxial single crystalline 3C-SiC
+ IBS of epitaxial single crystalline 3C-SiC
}
\footnotesize
\end{itemize}
\end{center}
-\begin{minipage}{7cm}
-\includegraphics[width=7cm]{ibs_3c-sic.eps}
+\begin{minipage}{6.9cm}
+\includegraphics[width=7cm]{ibs_3c-sic.eps}\\[-0.4cm]
+\begin{center}
+{\tiny
+ XTEM: single crystalline 3C-SiC in Si\hkl(1 0 0)
+}
+\end{center}
\end{minipage}
\begin{minipage}{5cm}
\begin{pspicture}(0,0)(0,0)
\end{itemize}
\end{minipage}
}}
-\rput(-6.8,5.4){\pnode{h0}}
-\rput(-3.0,5.4){\pnode{h1}}
+\rput(-6.8,5.5){\pnode{h0}}
+\rput(-3.0,5.5){\pnode{h1}}
\ncline[linecolor=blue]{-}{h0}{h1}
\ncline[linecolor=blue]{->}{h1}{box}
\end{pspicture}
\end{slide}
+\end{document}
+% temp
+\ifnum1=0
+
+% contents
+
+\begin{slide}
+
+\headphd
+{\large\bf
+ Outline
+}
+
+ \begin{itemize}
+ \item Supposed precipitation mechanism of SiC in Si
+ \item Utilized simulation techniques
+ \begin{itemize}
+ \item Molecular dynamics (MD) simulations
+ \item Density functional theory (DFT) calculations
+ \end{itemize}
+ \item C and Si self-interstitial point defects in silicon
+ \item Silicon carbide precipitation simulations
+ \item Summary / Conclusion
+ \end{itemize}
+
+\end{slide}
+
\begin{slide}
\headphd
\end{document}
+\fi
dear examiners, dear colleagues.
welcome everybody to the the defense of my doctor's thesis entitled ...
as usual, i would like to start with a small motivation,
-which in this case is a motivation with respect to the materials system, SiC.
+which in this case focuses on the materials system, SiC.
slide 2
-the semiconductor material SiC ...
+the semiconductor material SiC has remarkable physical and chemical properties,
+which make it a promising new material in various fields of applications.
+the wide band gap and high breakdown field
+as well as the high electron mobility and saturation drift velocity
+in conjunction with its unique thermal stability and conductivity
+unveil SiC as the ideal candidate for
+high-temperature, high-power and high-frequency electronic
+and opto-electronic devices.
+
+in fact light emission from SiC crystal rectifiers was observed
+already in the very beginning of the 20th century
+constituting the brirth of solid state optoelectronics.
+and indeed, the first blue light emitting diodes in 1990 were based on SiC.
+(nowadays superceded by direct band gap materials like GaN).
+
+the focus of SiC based applications, however,
+is in the area of solid state electronic devices
+experiencing revolutionary performance improvements enabled by its capabilities.
+devices can be designed much thinner with increased dopant concentrations
+resulting in highly efficient rectifier diodes and switching transistors.
+one example is displayed: a SiC based inverter with an efficiency of 98.5%
+designed by the frauenhofer institute for solar energy systems.
+therefore, SiC constitutes a promising candidate to become the key technology
+towards an extensive development and use of regenerative energies and emobility.
+
+moreover, due to the large bonding energy,
+SiC is a hard and chemical inert material
+suitable for applications under extreme conditions
+and for microelectromechanical systems.
+its radiation hardness allows the operation as a first wall reactor material
+and as electronic devices in space.
slide 3
+
+the stoichiometric composition of silicon and carbon
+is the only stable compound in the C/Si system.
+SiC is a mainly covalent material in which both,
+the Si and C atom are sp3 hybridized.
+the local order of the silicon and carbon atoms
+characterized by the tetrahedral bond is the same for all polytypes.
+however, more than 250 different polytypes exist,
+which differ in the one-dimensional stacking sequence of
+identical, close-packed SiC bilayers,
+which can be situated on one of three possible positions (abbreviated a,b,c).
+the stacking sequence of the most important polytypes is displayed here.
+the 3c polytype is the only cubic polytype.
+
+different polytypes exhibit different properties,
+which are listed in the table
+and compared to other technologically relevant semiconductor materials.
+Despite the lower charge carrier mobilities for low electric fields,
+SiC clearly outperforms Si.
+among the different polytypes, the cubic phase shows the highest
+break down field and saturation drift velocity.
+additionally, these properties are isotropic.
+thus, the cubic polytype is most effective for highly efficient
+high-performance electronic devices.
+
slide 4
+
+SiC is rarely found in nature and, thus, must be synthesized.
+it was first observed by moissan from a meteor crater in arizona.
+the fact that natural SiC is almost only observed
+as individual presolar SiC stardust grains near craters of meteorite impacts
+already indicates the complexity involved in the synthesis process.
+
+however, nowadays, much progress has been achieved in SiC thin film growth.
+indeed, commerically available semiconductor devices based on alpha SiC exist,
+although these are still extremely expensive.
+However, production of the advantageous 3c polytype material is less advanced.
+mismatches in the thermal expansion coefficient and the lattice parameter
+(with respect to the substrate) cause a considerable amount of defects,
+which is responsible for structural and electrical qualities
+that are not yet satisfactory.
+
+next to CVD and MBE, the ion beam synthesis technique, which consists of
+high dose ion implantation foolowed by a high-temperature annealing step
+turned out to constitute a promising method to form buried layers of SiC in Si.
+...
+
slide 5
+
+...
+
+and the task of this work is to gain insight into SiC precipitation in silicon.
+
slide 6
+
+this (insight) is achieved by atomistic simulations, which are explained after the assumed precipitation mechnisms present in literature are presented ...
+
slide 7
slide 8
slide 9
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