X-Git-Url: https://hackdaworld.org/gitweb/?a=blobdiff_plain;f=posic%2Ftalks%2Fseminar_2010.tex;h=5fe206d7d781e026aaae74b576584bda1ecaa399;hb=3e0cf069d29304120c01c063368bfa4d04365e57;hp=fd742bb16a7af6f81c6f1b287771f32ea9bb6208;hpb=3d5577359a78be2b7cf1f2fa6ab2db587f749f8f;p=lectures%2Flatex.git diff --git a/posic/talks/seminar_2010.tex b/posic/talks/seminar_2010.tex index fd742bb..5fe206d 100644 --- a/posic/talks/seminar_2010.tex +++ b/posic/talks/seminar_2010.tex @@ -26,6 +26,8 @@ \usepackage{graphicx} \graphicspath{{../img/}} +\usepackage{miller} + \usepackage[setpagesize=false]{hyperref} \usepackage{semcolor} @@ -172,15 +174,16 @@ } \begin{itemize} - \item Fabrication of silicon carbide - \item Precipitation model + \item Polyteps and fabrication of silicon carbide + \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 Point defects in silicon - \item Precipitation simulations + \item C and Si self-interstitial point defects in silicon + \item Silicon carbide precipitation simulations + \item Investigation of a silicon carbide precipitate in silicon \item Summary / Conclusion / Outlook \end{itemize} @@ -191,51 +194,674 @@ \begin{slide} {\large\bf - Motivation + Polytypes of SiC } + + \vspace{4cm} + + \small + +\begin{tabular}{l c c c c c c} +\hline + & 3C-SiC & 4H-SiC & 6H-SiC & Si & GaN & Diamond\\ +\hline +Hardness [Mohs] & \multicolumn{3}{c}{------ 9.6 ------}& 6.5 & - & 10 \\ +Band gap [eV] & 2.36 & 3.23 & 3.03 & 1.12 & 3.39 & 5.5 \\ +Break down field [$10^6$ V/cm] & 4 & 3 & 3.2 & 0.6 & 5 & 10 \\ +Saturation drift velocity [$10^7$ cm/s] & 2.5 & 2.0 & 2.0 & 1 & 2.7 & 2.7 \\ +Electron mobility [cm$^2$/Vs] & 800 & 900 & 400 & 1100 & 900 & 2200 \\ +Hole mobility [cm$^2$/Vs] & 320 & 120 & 90 & 420 & 150 & 1600 \\ +Thermal conductivity [W/cmK] & 5.0 & 4.9 & 4.9 & 1.5 & 1.3 & 22 \\ +\hline +\end{tabular} + +{\tiny + Values for $T=300$ K +} + +\begin{picture}(0,0)(-160,-155) + \includegraphics[width=7cm]{polytypes.eps} +\end{picture} +\begin{picture}(0,0)(-10,-185) + \includegraphics[width=3.8cm]{cubic_hex.eps}\\ +\end{picture} +\begin{picture}(0,0)(-10,-175) + {\tiny cubic (twist)} +\end{picture} +\begin{picture}(0,0)(-60,-175) + {\tiny hexagonal (no twist)} +\end{picture} +\begin{pspicture}(0,0)(0,0) +\psellipse[linecolor=green](5.7,3.03)(0.4,0.5) +\end{pspicture} +\begin{pspicture}(0,0)(0,0) +\psellipse[linecolor=green](5.6,1.68)(0.4,0.2) +\end{pspicture} +\begin{pspicture}(0,0)(0,0) +\psellipse[linecolor=red](10.7,1.13)(0.4,0.2) +\end{pspicture} + +\end{slide} + +\begin{slide} + + {\large\bf + Fabrication of silicon carbide + } + + \small \vspace{4pt} SiC - \emph{Born from the stars, perfected on earth.} - + \vspace{4pt} - Herstellung d"unner SiC-Filme: + Conventional thin film SiC growth: \begin{itemize} - \item modifizierter Lely-Prozess + \item \underline{Sublimation growth using the modified Lely method} \begin{itemize} - \item Impfkristall mit $T=2200 \, ^{\circ} \text{C}$ - \item umgeben von polykristallinen SiC mit - $T=2400 \, ^{\circ} \text{C}$ + \item SiC single-crystalline seed at $T=1800 \, ^{\circ} \text{C}$ + \item Surrounded by polycrystalline SiC in a graphite crucible\\ + at $T=2100-2400 \, ^{\circ} \text{C}$ + \item Deposition of supersaturated vapor on cooler seed crystal \end{itemize} - \item CVD Homoepitaxie + \item \underline{Homoepitaxial growth using CVD} \begin{itemize} - \item 'step controlled epitaxy' auf 6H-SiC-Substrat - \item C$_3$H$_8$/SiH$_4$/H$_2$ bei $1500 \, ^{\circ} \text{C}$ - \item Winkel $\rightarrow$ 3C/6H/4H-SiC - \item hohe Qualit"at aber limitiert durch\\ - Substratgr"o"se + \item Step-controlled epitaxy on off-oriented 6H-SiC substrates + \item C$_3$H$_8$/SiH$_4$/H$_2$ at $1100-1500 \, ^{\circ} \text{C}$ + \item Angle, temperature $\rightarrow$ 3C/6H/4H-SiC + \item High quality but limited in size of substrates \end{itemize} - \item CVD/MBE Heteroepitaxie von 3C-SiC auf Si + \item \underline{Heteroepitaxial growth of 3C-SiC on Si using CVD/MBE} \begin{itemize} - \item 2 Schritte: Karbonisierung und Wachstum + \item Two steps: carbonization and growth \item $T=650-1050 \, ^{\circ} \text{C}$ - \item Qualit"at/Gr"o"se noch nicht ausreichend + \item Quality and size not yet sufficient \end{itemize} \end{itemize} - \begin{picture}(0,0)(-245,-50) - \includegraphics[width=5cm]{6h-sic_3c-sic.eps} + \begin{picture}(0,0)(-280,-65) + \includegraphics[width=3.8cm]{6h-sic_3c-sic.eps} + \end{picture} + \begin{picture}(0,0)(-280,-55) + \begin{minipage}{5cm} + {\tiny + NASA: 6H-SiC and 3C-SiC LED\\[-7pt] + on 6H-SiC substrate + } + \end{minipage} + \end{picture} + \begin{picture}(0,0)(-265,-150) + \includegraphics[width=2.4cm]{m_lely.eps} \end{picture} - \begin{picture}(0,0)(-240,-35) + \begin{picture}(0,0)(-333,-175) \begin{minipage}{5cm} - {\scriptsize - NASA: 6H-SiC LED und 3C-SiC LED\\[-6pt] - nebeneinander auf 6H-SiC-Substrat + {\tiny + 1. Lid\\[-7pt] + 2. Heating\\[-7pt] + 3. Source\\[-7pt] + 4. Crucible\\[-7pt] + 5. Insulation\\[-7pt] + 6. Seed crystal } \end{minipage} \end{picture} \end{slide} +\begin{slide} + + {\large\bf + Fabrication of silicon carbide + } + + \small + + Alternative approach: + Ion beam synthesis (IBS) of burried 3C-SiC layers in Si\hkl(1 0 0) + \begin{itemize} + \item \underline{Implantation step 1}\\ + 180 keV C$^+$, $D=7.9\times 10^{17}$ cm$^{-2}$, $T_{\text{i}}=500\,^{\circ}\mathrm{C}$\\ + $\Rightarrow$ box-like distribution of equally sized + and epitactically oriented SiC precipitates + + \item \underline{Implantation step 2}\\ + 180 keV C$^+$, $D=0.6\times 10^{17}$ cm$^{-2}$, $T_{\text{i}}=250\,^{\circ}\mathrm{C}$\\ + $\Rightarrow$ destruction of SiC nanocrystals + in growing amorphous interface layers + \item \underline{Annealing}\\ + $T=1250\,^{\circ}\mathrm{C}$, $t=10\,\text{h}$\\ + $\Rightarrow$ homogeneous, stoichiometric SiC layer + with sharp interfaces + \end{itemize} + + \begin{minipage}{6.3cm} + \includegraphics[width=6cm]{ibs_3c-sic.eps}\\[-0.2cm] + {\tiny + XTEM micrograph of single crystalline 3C-SiC in Si\hkl(1 0 0) + } + \end{minipage} + \begin{minipage}{6.3cm} + \begin{center} + {\color{blue} + Precipitation mechanism not yet fully understood! + } + \renewcommand\labelitemi{$\Rightarrow$} + \small + \underline{Understanding 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{center} + \end{minipage} + +\end{slide} + +\begin{slide} + + {\large\bf + Supposed precipitation mechanism of SiC in Si + } + + \scriptsize + + \vspace{0.1cm} + + \begin{minipage}{3.8cm} + Si \& SiC lattice structure\\[0.2cm] + \includegraphics[width=3.5cm]{sic_unit_cell.eps}\\[-0.3cm] + \hrule + \end{minipage} + \hspace{0.6cm} + \begin{minipage}{3.8cm} + \begin{center} + \includegraphics[width=3.3cm]{tem_c-si-db.eps} + \end{center} + \end{minipage} + \hspace{0.6cm} + \begin{minipage}{3.8cm} + \begin{center} + \includegraphics[width=3.3cm]{tem_3c-sic.eps} + \end{center} + \end{minipage} + + \begin{minipage}{4cm} + \begin{center} + C-Si dimers (dumbbells)\\[-0.1cm] + on Si interstitial sites + \end{center} + \end{minipage} + \hspace{0.2cm} + \begin{minipage}{4.2cm} + \begin{center} + Agglomeration of C-Si dumbbells\\[-0.1cm] + $\Rightarrow$ dark contrasts + \end{center} + \end{minipage} + \hspace{0.2cm} + \begin{minipage}{4cm} + \begin{center} + Precipitation of 3C-SiC in Si\\[-0.1cm] + $\Rightarrow$ Moir\'e fringes\\[-0.1cm] + \& release of Si self-interstitials + \end{center} + \end{minipage} + + \begin{minipage}{3.8cm} + \begin{center} + \includegraphics[width=3.3cm]{sic_prec_seq_01.eps} + \end{center} + \end{minipage} + \hspace{0.6cm} + \begin{minipage}{3.8cm} + \begin{center} + \includegraphics[width=3.3cm]{sic_prec_seq_02.eps} + \end{center} + \end{minipage} + \hspace{0.6cm} + \begin{minipage}{3.8cm} + \begin{center} + \includegraphics[width=3.3cm]{sic_prec_seq_03.eps} + \end{center} + \end{minipage} + +\begin{pspicture}(0,0)(0,0) +\psline[linewidth=4pt]{->}(8.5,2)(9.0,2) +\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) +\end{pspicture} + +\end{slide} + +\begin{slide} + + {\large\bf + Molecular dynamics (MD) simulations + } + + \vspace{12pt} + + \small + + {\bf MD basics:} + \begin{itemize} + \item Microscopic description of N particle system + \item Analytical interaction potential + \item Numerical integration using Newtons equation of motion\\ + as a propagation rule in 6N-dimensional phase space + \item Observables obtained by time and/or ensemble averages + \end{itemize} + {\bf Details of the simulation:} + \begin{itemize} + \item Integration: Velocity Verlet, timestep: $1\text{ fs}$ + \item Ensemble: NpT (isothermal-isobaric) + \begin{itemize} + \item Berendsen thermostat: + $\tau_{\text{T}}=100\text{ fs}$ + \item Berendsen barostat:\\ + $\tau_{\text{P}}=100\text{ fs}$, + $\beta^{-1}=100\text{ GPa}$ + \end{itemize} + \item Erhart/Albe potential: Tersoff-like bond order potential + \vspace*{12pt} + \[ + E = \frac{1}{2} \sum_{i \neq j} \pot_{ij}, \quad + \pot_{ij} = f_C(r_{ij}) \left[ f_R(r_{ij}) + b_{ij} f_A(r_{ij}) \right] + \] + \end{itemize} + + \begin{picture}(0,0)(-230,-30) + \includegraphics[width=5cm]{tersoff_angle.eps} + \end{picture} + +\end{slide} + +\begin{slide} + + {\large\bf + Density functional theory (DFT) calculations + } + + \small + + Basic ingredients necessary for DFT + + \begin{itemize} + \item \underline{Hohenberg-Kohn theorem} - ground state density $n_0(r)$ ... + \begin{itemize} + \item ... uniquely determines the ground state potential + / wavefunctions + \item ... minimizes the systems total energy + \end{itemize} + \item \underline{Born-Oppenheimer} + - $N$ moving electrons in an external potential of static nuclei +\[ +H\Psi = \left[-\sum_i^N \frac{\hbar^2}{2m}\nabla_i^2 + +\sum_i^N V_{\text{ext}}(r_i) + +\sum_{i}{init}{insert} + \ncline[]{->}{insert}{cool} + \end{pspicture} +\end{minipage} +\begin{minipage}{5cm} + \includegraphics[width=5cm]{unit_cell_e.eps}\\ +\end{minipage} + +\begin{minipage}{9cm} + \begin{tabular}{l c c} + \hline + & size [unit cells] & \# atoms\\ +\hline +VASP & $3\times 3\times 3$ & $216\pm 1$ \\ +Erhart/Albe & $9\times 9\times 9$ & $5832\pm 1$\\ +\hline + \end{tabular} +\end{minipage} +\begin{minipage}{4cm} +{\color{red}$\bullet$} Tetrahedral\\ +{\color{green}$\bullet$} Hexagonal\\ +{\color{yellow}$\bullet$} \hkl<1 0 0> dumbbell\\ +{\color{magenta}$\bullet$} \hkl<1 1 0> dumbbell\\ +{\color{cyan}$\bullet$} Bond-centered\\ +{\color{black}$\bullet$} Vacancy / Substitutional +\end{minipage} + +\end{slide} + +\begin{slide} + + \footnotesize + +\begin{minipage}{9.5cm} + + {\large\bf + Si self-interstitial point defects in silicon\\ + } + +\begin{tabular}{l c c c c c} +\hline + $E_{\text{f}}$ [eV] & \hkl<1 1 0> DB & H & T & \hkl<1 0 0> DB & V \\ +\hline + VASP & \underline{3.39} & 3.42 & 3.77 & 4.41 & 3.63 \\ + Erhart/Albe & 4.39 & 4.48$^*$ & \underline{3.40} & 5.42 & 3.13 \\ +\hline +\end{tabular}\\[0.2cm] + +\begin{minipage}{4.7cm} +\includegraphics[width=4.7cm]{e_kin_si_hex.ps} +\end{minipage} +\begin{minipage}{4.7cm} +\begin{center} +{\tiny nearly T $\rightarrow$ T}\\ +\end{center} +\includegraphics[width=4.7cm]{nhex_tet.ps} +\end{minipage}\\ + +\underline{Hexagonal} \hspace{2pt} +\href{../video/si_self_int_hexa.avi}{$\rhd$}\\[0.1cm] +\framebox{ +\begin{minipage}{2.7cm} +$E_{\text{f}}^*=4.48\text{ eV}$\\ +\includegraphics[width=2.7cm]{si_pd_albe/hex_a.eps} +\end{minipage} +\begin{minipage}{0.4cm} +\begin{center} +$\Rightarrow$ +\end{center} +\end{minipage} +\begin{minipage}{2.7cm} +$E_{\text{f}}=3.96\text{ eV}$\\ +\includegraphics[width=2.8cm]{si_pd_albe/hex.eps} +\end{minipage} +} +\begin{minipage}{2.9cm} +\begin{flushright} +\underline{Vacancy}\\ +\includegraphics[width=3.0cm]{si_pd_albe/vac.eps} +\end{flushright} +\end{minipage} + +\end{minipage} +\begin{minipage}{3.5cm} + +\begin{flushright} +\underline{\hkl<1 1 0> dumbbell}\\ +\includegraphics[width=3.0cm]{si_pd_albe/110.eps}\\ +\underline{Tetrahedral}\\ +\includegraphics[width=3.0cm]{si_pd_albe/tet.eps}\\ +\underline{\hkl<1 0 0> dumbbell}\\ +\includegraphics[width=3.0cm]{si_pd_albe/100.eps} +\end{flushright} + +\end{minipage} + +\end{slide} + +\begin{slide} + +\footnotesize + + {\large\bf + C interstitial point defects in silicon\\[-0.1cm] + } + +\begin{tabular}{l c c c c c c} +\hline + $E_{\text{f}}$ & T & H & \hkl<1 0 0> DB & \hkl<1 1 0> DB & S & B \\ +\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$^*$ \\ +\hline +\end{tabular}\\[0.1cm] + +\framebox{ +\begin{minipage}{2.7cm} +\underline{Hexagonal} \hspace{2pt} +\href{../video/c_in_si_int_hexa.avi}{$\rhd$}\\ +$E_{\text{f}}^*=9.05\text{ eV}$\\ +\includegraphics[width=2.7cm]{c_pd_albe/hex.eps} +\end{minipage} +\begin{minipage}{0.4cm} +\begin{center} +$\Rightarrow$ +\end{center} +\end{minipage} +\begin{minipage}{2.7cm} +\underline{\hkl<1 0 0>}\\ +$E_{\text{f}}=3.88\text{ eV}$\\ +\includegraphics[width=2.7cm]{c_pd_albe/100.eps} +\end{minipage} +} +\begin{minipage}{2cm} +\hfill +\end{minipage} +\begin{minipage}{3cm} +\begin{flushright} +\underline{Tetrahedral}\\ +\includegraphics[width=3.0cm]{c_pd_albe/tet.eps} +\end{flushright} +\end{minipage} + +\framebox{ +\begin{minipage}{2.7cm} +\underline{Bond-centered}\\ +$E_{\text{f}}^*=5.59\text{ eV}$\\ +\includegraphics[width=2.7cm]{c_pd_albe/bc.eps} +\end{minipage} +\begin{minipage}{0.4cm} +\begin{center} +$\Rightarrow$ +\end{center} +\end{minipage} +\begin{minipage}{2.7cm} +\underline{\hkl<1 1 0> dumbbell}\\ +$E_{\text{f}}=5.18\text{ eV}$\\ +\includegraphics[width=2.7cm]{c_pd_albe/110.eps} +\end{minipage} +} +\begin{minipage}{2cm} +\hfill +\end{minipage} +\begin{minipage}{3cm} +\begin{flushright} +\underline{Substitutional}\\ +\includegraphics[width=3.0cm]{c_pd_albe/sub.eps} +\end{flushright} +\end{minipage} + +\end{slide} + +\begin{slide} + +\footnotesize + + {\large\bf\boldmath + C \hkl<1 0 0> dumbbell interstitial configuration\\ + } + +{\tiny +\begin{tabular}{l c c c c c c c c} +\hline + Distances & $r(1C)$ & $r(2C)$ & $r(3C)$ & $r(12)$ & $r(13)$ & $r(34)$ & $r(23)$ & $r(25)$ \\ +\hline +Erhart/Albe & 0.175 & 0.329 & 0.186 & 0.226 & 0.300 & 0.343 & 0.423 & 0.425 \\ +VASP & 0.174 & 0.341 & 0.182 & 0.229 & 0.286 & 0.347 & 0.422 & 0.417 \\ +\hline +\end{tabular}\\[0.2cm] +\begin{tabular}{l c c c c } +\hline + Angles & $\theta_1$ & $\theta_2$ & $\theta_3$ & $\theta_4$ \\ +\hline +Erhart/Albe & 140.2 & 109.9 & 134.4 & 112.8 \\ +VASP & 130.7 & 114.4 & 146.0 & 107.0 \\ +\hline +\end{tabular}\\[0.2cm] +\begin{tabular}{l c c c} +\hline + Displacements & $a$ & $b$ & $|a|+|b|$ \\ +\hline +Erhart/Albe & 0.084 & -0.091 & 0.175 \\ +VASP & 0.109 & -0.065 & 0.174 \\ +\hline +\end{tabular}\\[0.6cm] +} + +\begin{minipage}{3.0cm} +\begin{center} +\underline{Erhart/Albe} +\includegraphics[width=3.0cm]{c_pd_albe/100_cmp.eps} +\end{center} +\end{minipage} +\begin{minipage}{3.0cm} +\begin{center} +\underline{VASP} +\includegraphics[width=3.0cm]{c_pd_vasp/100_cmp.eps} +\end{center} +\end{minipage}\\ + +\begin{picture}(0,0)(-185,10) +\includegraphics[width=6.8cm]{100-c-si-db_cmp.eps} +\end{picture} +\begin{picture}(0,0)(-280,-150) +\includegraphics[width=3.3cm]{c_pd_vasp/eden.eps} +\end{picture} + +\end{slide} + +\begin{slide} + +\footnotesize + + {\large\bf + Bond-centered interstitial configuration\\ + } + + +\end{slide} + +\begin{slide} + + {\large\bf + Silicon carbide precipitation simulations + } + + \small + +\end{slide} + +\begin{slide} + + {\large\bf + Investigation of a silicon carbide precipitate in silicon + } + + \small + +\end{slide} + \end{document}