From b6eea3257a112b76d436da677b76d90b68b605a5 Mon Sep 17 00:00:00 2001 From: hackbard Date: Wed, 25 May 2011 23:53:06 +0200 Subject: [PATCH] security checkin --- posic/talks/seminar_2011.tex | 246 +++++++++++++++-------------------- 1 file changed, 103 insertions(+), 143 deletions(-) diff --git a/posic/talks/seminar_2011.tex b/posic/talks/seminar_2011.tex index 988543e..ca6b07f 100644 --- a/posic/talks/seminar_2011.tex +++ b/posic/talks/seminar_2011.tex @@ -31,6 +31,9 @@ \usepackage[setpagesize=false]{hyperref} +% units +\usepackage{units} + \usepackage{semcolor} \usepackage{semlayer} % Seminar overlays \usepackage{slidesec} % Seminar sections and list of slides @@ -85,6 +88,15 @@ \newrgbcolor{hlbb}{0.825 0.88 0.968} \newrgbcolor{lachs}{1.0 .93 .81} +% shortcuts +\newcommand{\si}{Si$_{\text{i}}${}} +\newcommand{\ci}{C$_{\text{i}}${}} +\newcommand{\cs}{C$_{\text{sub}}${}} +\newcommand{\degc}[1]{\unit[#1]{$^{\circ}$C}{}} +\newcommand{\distn}[1]{\unit[#1]{nm}{}} +\newcommand{\dista}[1]{\unit[#1]{\AA}{}} +\newcommand{\perc}[1]{\unit[#1]{\%}{}} + % topic \begin{slide} @@ -103,11 +115,11 @@ \vspace{48pt} -Yet another seminar contribution +Yet another seminar talk \vspace{08pt} - Augsburg am 26. Mai 2011 + Augsburg, 26. Mai 2011 \end{center} \end{slide} @@ -751,12 +763,12 @@ $E_{\text{f}}=3.96\text{ eV}$\\ C interstitial point defects in silicon\\[-0.1cm] } -\begin{tabular}{l c c c c c c} +\begin{tabular}{l c c c c c c r} \hline - $E_{\text{f}}$ & T & H & \hkl<1 0 0> DB & \hkl<1 1 0> DB & S & B \\ + $E_{\text{f}}$ & T & H & \hkl<1 0 0> DB & \hkl<1 1 0> DB & S & B & \cs{} \& \si\\ \hline - VASP & unstable & unstable & \underline{3.72} & 4.16 & 1.95 & 4.66 \\ - Erhart/Albe MD & 6.09 & 9.05$^*$ & \underline{3.88} & 5.18 & 0.75 & 5.59$^*$ \\ + VASP & unstable & unstable & \underline{3.72} & 4.16 & 1.95 & 4.66 & {\color{green}4.17}\\ + Erhart/Albe MD & 6.09 & 9.05$^*$ & \underline{3.88} & 5.18 & {\color{red}0.75} & 5.59$^*$ & {\color{green}4.43} \\ \hline \end{tabular}\\[0.1cm] @@ -1193,10 +1205,12 @@ VASP results \scriptsize + \vspace{0.1cm} + \begin{minipage}{6.5cm} \framebox{ -\begin{minipage}{5.9cm} +\begin{minipage}[t]{5.9cm} \begin{flushleft} \includegraphics[width=5.9cm]{bc_00-1.ps}\\[2.35cm] \end{flushleft} @@ -1250,7 +1264,6 @@ Erhart/Albe results \item Lowest activation energy: $\approx$ 2.2 eV \item 2.4 times higher than VASP \item Different pathway - \item Transition minima ($\rightarrow$ \hkl<1 1 0> dumbbell) \end{itemize} \end{minipage} @@ -1259,38 +1272,51 @@ Erhart/Albe results \framebox{ \begin{minipage}{5.9cm} -\begin{flushright} -\includegraphics[width=5.9cm]{00-1_0-10.ps}\\[0.75cm] -\end{flushright} -\begin{center} -\begin{pspicture}(0,0)(0,0) -\psframe[linecolor=red,fillstyle=none](-2.8,-0.25)(3.3,1.1) -\end{pspicture} -\begin{picture}(0,0)(60,-5) -\includegraphics[width=0.9cm]{albe_mig/00-1_0-10_red_00.eps} -\end{picture} -\begin{picture}(0,0)(0,-5) -\includegraphics[width=0.9cm]{albe_mig/00-1_0-10_red_min.eps} -\end{picture} -\begin{picture}(0,0)(-55,-5) -\includegraphics[width=0.9cm]{albe_mig/00-1_0-10_red_03.eps} -\end{picture} -\begin{picture}(0,0)(12.5,5) -\includegraphics[width=1cm]{100_arrow.eps} -\end{picture} -\begin{picture}(0,0)(90,0) -\includegraphics[height=0.9cm]{001_arrow.eps} -\end{picture} -\end{center} -\vspace{0.2cm} +%\begin{flushright} +%\includegraphics[width=5.9cm]{00-1_0-10.ps}\\[0.75cm] +%\end{flushright} +%\begin{center} +%\begin{pspicture}(0,0)(0,0) +%\psframe[linecolor=red,fillstyle=none](-2.8,-0.25)(3.3,1.1) +%\end{pspicture} +%\begin{picture}(0,0)(60,-5) +%\includegraphics[width=0.9cm]{albe_mig/00-1_0-10_red_00.eps} +%\end{picture} +%\begin{picture}(0,0)(0,-5) +%\includegraphics[width=0.9cm]{albe_mig/00-1_0-10_red_min.eps} +%\end{picture} +%\begin{picture}(0,0)(-55,-5) +%\includegraphics[width=0.9cm]{albe_mig/00-1_0-10_red_03.eps} +%\end{picture} +%\begin{picture}(0,0)(12.5,5) +%\includegraphics[width=1cm]{100_arrow.eps} +%\end{picture} +%\begin{picture}(0,0)(90,0) +%\includegraphics[height=0.9cm]{001_arrow.eps} +%\end{picture} +%\end{center} +%\vspace{0.2cm} +%\end{minipage} +%}\\[0.2cm] +% +%\framebox{ +%\begin{minipage}{5.9cm} +\includegraphics[width=5.9cm]{00-1_110_0-10_mig_albe.ps} \end{minipage} -}\\[0.2cm] +}\\[0.1cm] -\framebox{ \begin{minipage}{5.9cm} -\includegraphics[width=5.9cm]{00-1_ip0-10.ps} +Transition involving \ci{} \hkl<1 1 0> +\begin{itemize} + \item Bond-centered configuration unstable\\ + $\rightarrow$ \ci{} \hkl<1 1 0> dumbbell + \item Transition minima of path 2 \& 3\\ + $\rightarrow$ \ci{} \hkl<1 1 0> dumbbell + \item Activation energy: $\approx$ 2.2 eV \& 0.9 eV + \item 2.4 - 3.4 times higher than VASP + \item Rotation of dumbbell orientation +\end{itemize} \end{minipage} -} \end{minipage} @@ -1569,7 +1595,7 @@ $r$ [nm] & 0.292 & 0.394 & 0.241 & 0.453 & 0.407 & 0.408 & 0.452 & 0.392 & 0.456 Conclusion of defect / migration / combined defect simulations } - \small + \footnotesize \vspace*{0.1cm} @@ -1577,34 +1603,36 @@ Defect structures \begin{itemize} \item Accurately described by quantum-mechanical simulations \item Less accurate description by classical potential simulations + \item Underestimated formation energy of \cs{} by classical approach + \item Both methods predict same ground state: \ci{} \hkl<1 0 0> dumbbell \end{itemize} -\vspace*{0.2cm} + +Migration \begin{itemize} - \item \hkl<1 0 0> C-Si dumbbell interstitial ground state configuration - \item Consistent with reorientation and diffusion experiments \item C migration pathway in Si identified + \item Consistent with reorientation and diffusion experiments +\end{itemize} +\begin{itemize} + \item Different path and ... + \item overestimated barrier by classical potential calculations \end{itemize} Concerning the precipitation mechanism \begin{itemize} \item Agglomeration of C-Si dumbbells energetically favorable + (stress compensation) \item C-Si indeed favored compared to C$_{\text{sub}}$ \& \hkl<1 1 0> Si self-interstitial \item Possible low interaction capture radius of C$_{\text{sub}}$ \& \hkl<1 1 0> Si self-interstitial + \item Low barrier for + \ci{} \hkl<1 0 0> $\rightarrow$ \cs{} \& \si{} \hkl<1 1 0> \item In absence of nearby \hkl<1 1 0> Si self-interstitial: C-Si \hkl<1 0 0> + Vacancy $\rightarrow$ C$_{\text{sub}}$ (SiC) \end{itemize} \begin{center} -{\color{blue}Some results point to a different precipitation mechanism!} +{\color{blue}Results suggest increased participation of \cs} \end{center} -In progress ... -\begin{itemize} - \item \hkl<1 0 0> C-Si $\rightarrow$ - C$_{\text{sub}}$ \& \hkl<1 1 0> Si self-interstitial - \item \hkl<1 0 0> C-Si combinations: C-C $\rightarrow$ C-...-C -\end{itemize} - \end{slide} @@ -1898,7 +1926,7 @@ $\Rightarrow$ indicate slight {\color{blue}acceleration of dynamics} due to temperature\\[0.1cm] \framebox{ \bf -Continue with higher temperatures and longer time scales +Actual SiC precipitation not accessible by MD } \end{center} @@ -1907,63 +1935,7 @@ Continue with higher temperatures and longer time scales \begin{slide} {\large\bf - Long time scale simulations at maximum temperature - } - -\small - -\vspace{0.1cm} - -\underline{Differences} -\begin{itemize} - \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} - -\footnotesize - -\vspace{0.3cm} - -\begin{minipage}[t]{4.5cm} -\begin{center} -\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\\ -C-Si-Si $\uparrow$\\ -C-Si-C $\downarrow$ -\end{center} -\end{minipage} - -\begin{center} -\framebox{ -Long time scales and high temperatures most probably not sufficient enough! -} -\end{center} - -\end{slide} - -\begin{slide} - - {\large\bf - Summary / Conclusion / Outlook + Summary and Conclusions } \scriptsize @@ -1974,29 +1946,26 @@ Long time scales and high temperatures most probably not sufficient enough! \begin{minipage}{12.9cm} \underline{Defects} \begin{itemize} - \item Summary \& conclusion + \item DFT / EA \begin{itemize} \item Point defects excellently / fairly well described - by QM / classical potential simulations + by DFT / EA + \item C$_{\text{sub}}$ drastically underestimated by EA + \item EA predicts correct ground state: + C$_{\text{sub}}$ \& \si{} $>$ \ci{} \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) + diffusion and reorientation experiments by DFT + \item EA fails to describe \ci{} migration: + Wrong path \& overestimated barrier \end{itemize} - \item In progress - \begin{itemize} - \item Migrations separating C-C bond in \hkl<1 0 0> C-Si dumbbell - interstitial combination - \item Migration: \hkl<1 0 0> C-Si $\rightarrow$ - C$_{\text{sub}}$ \& Si \hkl<1 1 0> interstitial - \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) + \item Combinations of defects + \begin{itemize} + \item Agglomeration of point defects energetically favorable + by compensation of stress + \item Formation of C-C unlikely + \item C$_{\text{sub}}$ favored conditions (conceivable in IBS) + \item \ci{} \hkl<1 0 0> $\leftrightarrow$ \cs{} \& \si{} \hkl<1 1 0>\\ + Low barrier (\unit[0.77]{eV}) \& low capture radius \end{itemize} \end{itemize} \end{minipage} @@ -2008,27 +1977,18 @@ Long time scales and high temperatures most probably not sufficient enough! \begin{minipage}[t]{12.9cm} \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} + \item High C concentration $\rightarrow$ amorphous SiC like phase + \item Problem of potential enhanced slow phase space propagation + \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 Precipitation by successive agglomeration of \cs (epitaxy) + \item \si{}: vehicle to form \cs{} \& supply of Si \& stress compensation + (stretched SiC, interface) \end{itemize} \end{minipage} } - \small - \end{slide} \begin{slide} @@ -2045,7 +2005,7 @@ Long time scales and high temperatures most probably not sufficient enough! \underline{Augsburg} \begin{itemize} - \item Prof. B. Stritzker (accepting a simulator at EP \RM{4}) + \item Prof. B. Stritzker (accomodation at EP \RM{4}) \item Ralf Utermann (EDV) \end{itemize} -- 2.39.2