From: hackbard Date: Mon, 2 Jan 2012 16:31:28 +0000 (+0100) Subject: more defense talk ... X-Git-Url: https://hackdaworld.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a08cd67251d6433ee23653e567601260436c923a;p=lectures%2Flatex.git more defense talk ... --- diff --git a/posic/talks/defense.tex b/posic/talks/defense.tex index a8062e8..c6cb981 100644 --- a/posic/talks/defense.tex +++ b/posic/talks/defense.tex @@ -142,23 +142,26 @@ E\\ \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} @@ -166,6 +169,9 @@ E\\ % no vertical centering \centerslidesfalse +% skip for preparation +\ifnum1=0 + % intro % motivation / properties / applications of silicon carbide @@ -243,9 +249,11 @@ E\\ \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)} @@ -288,6 +296,8 @@ Thermal conductivity [W/cmK] & 5.0 & 4.9 & 4.9 & 1.5 & 1.3 & 22 \\ \end{slide} +\fi + % fabrication \begin{slide} @@ -321,13 +331,15 @@ SiC thin films by MBE \& CVD \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 @@ -350,36 +362,13 @@ Ion beam synthesis (IBS) of burried 3C-SiC layers in Si\hkl(1 0 0) \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} @@ -387,7 +376,7 @@ Ion beam synthesis (IBS) of burried 3C-SiC layers in Si\hkl(1 0 0) \headphd {\large\bf - Formation of epitaxial single crystalline 3C-SiC + IBS of epitaxial single crystalline 3C-SiC } \footnotesize @@ -410,8 +399,13 @@ Ion beam synthesis (IBS) of burried 3C-SiC layers in Si\hkl(1 0 0) \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) @@ -435,8 +429,8 @@ Ion beam synthesis (IBS) of burried 3C-SiC layers in Si\hkl(1 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} @@ -444,6 +438,33 @@ Ion beam synthesis (IBS) of burried 3C-SiC layers in Si\hkl(1 0 0) \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 @@ -2277,3 +2298,4 @@ Investigation of structure \& structural evolution \ldots \end{document} +\fi diff --git a/posic/talks/defense.txt b/posic/talks/defense.txt index 83f618d..25514aa 100644 --- a/posic/talks/defense.txt +++ b/posic/talks/defense.txt @@ -3,16 +3,100 @@ slide 1 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