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[lectures/latex.git] / posic / talks / seminar_2010.tex
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30
31 \usepackage[setpagesize=false]{hyperref}
32
33 \usepackage{semcolor}
34 \usepackage{semlayer}           % Seminar overlays
35 \usepackage{slidesec}           % Seminar sections and list of slides
36
37 \input{seminar.bug}             % Official bugs corrections
38 \input{seminar.bg2}             % Unofficial bugs corrections
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43
44 % font
45 %\usepackage{cmbright}
46 %\renewcommand{\familydefault}{\sfdefault}
47 %\usepackage{mathptmx}
48
49 \usepackage{upgreek}
50
51 \begin{document}
52
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57
58 % specify width and height
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60 \slideheight 19.1cm 
61
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80
81 % topic
82
83 \begin{slide}
84 \begin{center}
85
86  \vspace{16pt}
87
88  {\LARGE\bf
89   Atomistic simulation study of the silicon carbide precipitation
90   in silicon
91  }
92
93  \vspace{48pt}
94
95  \textsc{F. Zirkelbach}
96
97  \vspace{48pt}
98
99  Lehrstuhlseminar
100
101  \vspace{08pt}
102
103  17. Juni 2010
104
105 \end{center}
106 \end{slide}
107
108 % motivation / properties / applications of silicon carbide
109 \begin{slide}
110
111 \small
112
113 \begin{pspicture}(0,0)(13.5,5)
114
115
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121
122  \rput[lt](0.2,4.6){\color{gray}PROPERTIES}
123
124  \rput[lt](0.5,4){wide band gap}
125  \rput[lt](0.5,3.5){high electric breakdown field}
126  \rput[lt](0.5,3){good electron mobility}
127  \rput[lt](0.5,2.5){high electron saturation drift velocity}
128  \rput[lt](0.5,2){high thermal conductivity}
129
130  \rput[lt](0.5,1.5){hard and mechanically stable}
131  \rput[lt](0.5,1){chemically inert}
132
133  \rput[lt](0.5,0.5){radiation hardness}
134
135  \rput[rt](13.3,4.6){\color{gray}APPLICATIONS}
136
137  \rput[rt](13,3.85){high-temperature, high power}
138  \rput[rt](13,3.5){and high-frequency}
139  \rput[rt](13,3.15){electronic and optoelectronic devices}
140
141  \rput[rt](13,2.35){material suitable for extreme conditions}
142  \rput[rt](13,2){microelectromechanical systems}
143  \rput[rt](13,1.65){abrasives, cutting tools, heating elements}
144
145  \rput[rt](13,0.85){first wall reactor material, detectors}
146  \rput[rt](13,0.5){and electronic devices for space}
147
148 \end{pspicture}
149
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151 \includegraphics[width=2.6cm]{wide_band_gap.eps}
152 \end{picture}
153 \begin{picture}(0,0)(-295,-165)
154 \includegraphics[width=3cm]{sic_led.eps}
155 \end{picture}
156 \begin{picture}(0,0)(-215,-165)
157 \includegraphics[width=2.5cm]{6h-sic_3c-sic.eps}
158 \end{picture}
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162 \begin{picture}(0,0)(-220,65)
163 \includegraphics[width=2.9cm]{sic_wechselrichter_ise.eps}
164 \end{picture}
165
166 \end{slide}
167
168 % contents
169
170 \begin{slide}
171
172 {\large\bf
173  Outline
174 }
175
176  \begin{itemize}
177   \item Polyteps and fabrication of silicon carbide
178   \item Supposed precipitation mechanism of SiC in Si
179   \item Utilized simulation techniques
180         \begin{itemize}
181          \item Molecular dynamics (MD) simulations
182          \item Density functional theory (DFT) calculations
183         \end{itemize}
184   \item C and Si self-interstitial point defects in silicon
185   \item Silicon carbide precipitation simulations
186   \item Investigation of a silicon carbide precipitate in silicon
187   \item Summary / Conclusion / Outlook
188  \end{itemize}
189
190 \end{slide}
191
192 % start of contents
193
194 \begin{slide}
195
196  {\large\bf
197   Polytypes of SiC
198  }
199
200  \vspace{4cm}
201
202  \small
203
204 \begin{tabular}{l c c c c c c}
205 \hline
206  & 3C-SiC & 4H-SiC & 6H-SiC & Si & GaN & Diamond\\
207 \hline
208 Hardness [Mohs] & \multicolumn{3}{c}{------ 9.6 ------}& 6.5 & - & 10 \\
209 Band gap [eV] & 2.36 & 3.23 & 3.03 & 1.12 & 3.39 & 5.5 \\
210 Break down field [$10^6$ V/cm] & 4 & 3 & 3.2 & 0.6 & 5 & 10 \\
211 Saturation drift velocity [$10^7$ cm/s] & 2.5 & 2.0 & 2.0 & 1 & 2.7 & 2.7 \\
212 Electron mobility [cm$^2$/Vs] & 800 & 900 & 400 & 1100 & 900 & 2200 \\
213 Hole mobility [cm$^2$/Vs] & 320 & 120 & 90 & 420 & 150 & 1600 \\
214 Thermal conductivity [W/cmK] & 5.0 & 4.9 & 4.9 & 1.5 & 1.3 & 22 \\
215 \hline
216 \end{tabular}
217
218 {\tiny
219  Values for $T=300$ K
220 }
221
222 \begin{picture}(0,0)(-160,-155)
223  \includegraphics[width=7cm]{polytypes.eps}
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228 \begin{picture}(0,0)(-10,-175)
229  {\tiny cubic (twist)}
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232  {\tiny hexagonal (no twist)}
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243
244 \end{slide}
245
246 \begin{slide}
247
248  {\large\bf
249   Fabrication of silicon carbide
250  }
251
252  \small
253  
254  \vspace{4pt}
255
256  SiC - \emph{Born from the stars, perfected on earth.}
257  
258  \vspace{4pt}
259
260  Conventional thin film SiC growth:
261  \begin{itemize}
262   \item \underline{Sublimation growth using the modified Lely method}
263         \begin{itemize}
264          \item SiC single-crystalline seed at $T=1800 \, ^{\circ} \text{C}$
265          \item Surrounded by polycrystalline SiC in a graphite crucible\\
266                at $T=2100-2400 \, ^{\circ} \text{C}$
267          \item Deposition of supersaturated vapor on cooler seed crystal
268         \end{itemize}
269   \item \underline{Homoepitaxial growth using CVD}
270         \begin{itemize}
271          \item Step-controlled epitaxy on off-oriented 6H-SiC substrates
272          \item C$_3$H$_8$/SiH$_4$/H$_2$ at $1100-1500 \, ^{\circ} \text{C}$
273          \item Angle, temperature $\rightarrow$ 3C/6H/4H-SiC
274          \item High quality but limited in size of substrates
275         \end{itemize}
276   \item \underline{Heteroepitaxial growth of 3C-SiC on Si using CVD/MBE}
277         \begin{itemize}
278          \item Two steps: carbonization and growth
279          \item $T=650-1050 \, ^{\circ} \text{C}$
280          \item Quality and size not yet sufficient
281         \end{itemize}
282  \end{itemize}
283
284  \begin{picture}(0,0)(-280,-65)
285   \includegraphics[width=3.8cm]{6h-sic_3c-sic.eps}
286  \end{picture}
287  \begin{picture}(0,0)(-280,-55)
288   \begin{minipage}{5cm}
289   {\tiny
290    NASA: 6H-SiC and 3C-SiC LED\\[-7pt]
291    on 6H-SiC substrate
292   }
293   \end{minipage}
294  \end{picture}
295  \begin{picture}(0,0)(-265,-150)
296   \includegraphics[width=2.4cm]{m_lely.eps}
297  \end{picture}
298  \begin{picture}(0,0)(-333,-175)
299   \begin{minipage}{5cm}
300   {\tiny
301    1. Lid\\[-7pt]
302    2. Heating\\[-7pt]
303    3. Source\\[-7pt]
304    4. Crucible\\[-7pt]
305    5. Insulation\\[-7pt]
306    6. Seed crystal
307   }
308   \end{minipage}
309  \end{picture}
310
311 \end{slide}
312
313 \begin{slide}
314
315  {\large\bf
316   Fabrication of silicon carbide
317  }
318
319  \small
320
321  Alternative approach:
322  Ion beam synthesis (IBS) of burried 3C-SiC layers in Si\hkl(1 0 0)
323  \begin{itemize}
324   \item \underline{Implantation step 1}\\
325         180 keV C$^+$, $D=7.9\times 10^{17}$ cm$^{-2}$, $T_{\text{i}}=500\,^{\circ}\mathrm{C}$\\
326         $\Rightarrow$ box-like distribution of equally sized
327                        and epitactically oriented SiC precipitates
328                        
329   \item \underline{Implantation step 2}\\
330         180 keV C$^+$, $D=0.6\times 10^{17}$ cm$^{-2}$, $T_{\text{i}}=250\,^{\circ}\mathrm{C}$\\
331         $\Rightarrow$ destruction of SiC nanocrystals
332                       in growing amorphous interface layers
333   \item \underline{Annealing}\\
334         $T=1250\,^{\circ}\mathrm{C}$, $t=10\,\text{h}$\\
335         $\Rightarrow$ homogeneous, stoichiometric SiC layer
336                       with sharp interfaces
337  \end{itemize}
338
339  \begin{minipage}{6.3cm}
340  \includegraphics[width=6cm]{ibs_3c-sic.eps}\\[-0.2cm]
341  {\tiny
342   XTEM micrograph of single crystalline 3C-SiC in Si\hkl(1 0 0)
343  }
344  \end{minipage}
345 \framebox{
346  \begin{minipage}{6.3cm}
347  \begin{center}
348  {\color{blue}
349   Precipitation mechanism not yet fully understood!
350  }
351  \renewcommand\labelitemi{$\Rightarrow$}
352  \small
353  \underline{Understanding the SiC precipitation}
354  \begin{itemize}
355   \item significant technological progress in SiC thin film formation
356   \item perspectives for processes relying upon prevention of SiC precipitation
357  \end{itemize}
358  \end{center}
359  \end{minipage}
360 }
361  
362 \end{slide}
363
364 \begin{slide}
365
366  {\large\bf
367   Supposed precipitation mechanism of SiC in Si
368  }
369
370  \scriptsize
371
372  \vspace{0.1cm}
373
374  \begin{minipage}{3.8cm}
375  Si \& SiC lattice structure\\[0.2cm]
376  \includegraphics[width=3.5cm]{sic_unit_cell.eps}\\[-0.3cm]
377  \hrule
378  \end{minipage}
379  \hspace{0.6cm}
380  \begin{minipage}{3.8cm}
381  \begin{center}
382  \includegraphics[width=3.3cm]{tem_c-si-db.eps}
383  \end{center}
384  \end{minipage}
385  \hspace{0.6cm}
386  \begin{minipage}{3.8cm}
387  \begin{center}
388  \includegraphics[width=3.3cm]{tem_3c-sic.eps}
389  \end{center}
390  \end{minipage}
391
392  \begin{minipage}{4cm}
393  \begin{center}
394  C-Si dimers (dumbbells)\\[-0.1cm]
395  on Si interstitial sites
396  \end{center}
397  \end{minipage}
398  \hspace{0.2cm}
399  \begin{minipage}{4.2cm}
400  \begin{center}
401  Agglomeration of C-Si dumbbells\\[-0.1cm]
402  $\Rightarrow$ dark contrasts
403  \end{center}
404  \end{minipage}
405  \hspace{0.2cm}
406  \begin{minipage}{4cm}
407  \begin{center}
408  Precipitation of 3C-SiC in Si\\[-0.1cm]
409  $\Rightarrow$ Moir\'e fringes\\[-0.1cm]
410  \& release of Si self-interstitials
411  \end{center}
412  \end{minipage}
413
414  \begin{minipage}{3.8cm}
415  \begin{center}
416  \includegraphics[width=3.3cm]{sic_prec_seq_01.eps}
417  \end{center}
418  \end{minipage}
419  \hspace{0.6cm}
420  \begin{minipage}{3.8cm}
421  \begin{center}
422  \includegraphics[width=3.3cm]{sic_prec_seq_02.eps}
423  \end{center}
424  \end{minipage}
425  \hspace{0.6cm}
426  \begin{minipage}{3.8cm}
427  \begin{center}
428  \includegraphics[width=3.3cm]{sic_prec_seq_03.eps}
429  \end{center}
430  \end{minipage}
431
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437 \end{pspicture}
438  
439 \end{slide}
440
441 \begin{slide}
442
443  {\large\bf
444   Molecular dynamics (MD) simulations
445  }
446
447  \vspace{12pt}
448
449  \small
450
451  {\bf MD basics:}
452  \begin{itemize}
453   \item Microscopic description of N particle system
454   \item Analytical interaction potential
455   \item Numerical integration using Newtons equation of motion\\
456         as a propagation rule in 6N-dimensional phase space
457   \item Observables obtained by time and/or ensemble averages
458  \end{itemize}
459  {\bf Details of the simulation:}
460  \begin{itemize}
461   \item Integration: Velocity Verlet, timestep: $1\text{ fs}$
462   \item Ensemble: NpT (isothermal-isobaric)
463         \begin{itemize}
464          \item Berendsen thermostat:
465                $\tau_{\text{T}}=100\text{ fs}$
466          \item Berendsen barostat:\\
467                $\tau_{\text{P}}=100\text{ fs}$,
468                $\beta^{-1}=100\text{ GPa}$
469         \end{itemize}
470   \item Erhart/Albe potential: Tersoff-like bond order potential
471   \vspace*{12pt}
472         \[
473         E = \frac{1}{2} \sum_{i \neq j} \pot_{ij}, \quad
474         \pot_{ij} = f_C(r_{ij}) \left[ f_R(r_{ij}) + b_{ij} f_A(r_{ij}) \right]
475         \]
476  \end{itemize}
477
478  \begin{picture}(0,0)(-230,-30)
479   \includegraphics[width=5cm]{tersoff_angle.eps} 
480  \end{picture}
481  
482 \end{slide}
483
484 \begin{slide}
485
486  {\large\bf
487   Density functional theory (DFT) calculations
488  }
489
490  \small
491
492  Basic ingredients necessary for DFT
493
494  \begin{itemize}
495   \item \underline{Hohenberg-Kohn theorem} - ground state density $n_0(r)$ ...
496         \begin{itemize}
497          \item ... uniquely determines the ground state potential
498                / wavefunctions
499          \item ... minimizes the systems total energy
500         \end{itemize}
501   \item \underline{Born-Oppenheimer}
502         - $N$ moving electrons in an external potential of static nuclei
503 \[
504 H\Psi = \left[-\sum_i^N \frac{\hbar^2}{2m}\nabla_i^2
505               +\sum_i^N V_{\text{ext}}(r_i)
506               +\sum_{i<j}^N V_{e-e}(r_i,r_j)\right]\Psi=E\Psi
507 \]
508   \item \underline{Effective potential}
509         - averaged electrostatic potential \& exchange and correlation
510 \[
511 V_{\text{eff}}(r)=V_{\text{ext}}(r)+\int\frac{e^2 n(r')}{|r-r'|}d^3r'
512                  +V_{\text{XC}}[n(r)]
513 \]
514   \item \underline{Kohn-Sham system}
515         - Schr\"odinger equation of N non-interacting particles
516 \[
517 \left[ -\frac{\hbar^2}{2m}\nabla^2 + V_{\text{eff}}(r) \right] \Phi_i(r)
518 =\epsilon_i\Phi_i(r)
519 \quad
520 \Rightarrow
521 \quad
522 n(r)=\sum_i^N|\Phi_i(r)|^2
523 \]
524   \item \underline{Self-consistent solution}\\
525 $n(r)$ depends on $\Phi_i$, which depends on $V_{\text{eff}}$,
526 which in turn depends on $n(r)$
527   \item \underline{Variational principle}
528         - minimize total energy with respect to $n(r)$
529  \end{itemize}
530
531 \end{slide}
532
533 \begin{slide}
534
535  {\large\bf
536   Density functional theory (DFT) calculations
537  }
538
539  \small
540
541  \vspace*{0.2cm}
542
543  Details of applied DFT calculations in this work
544
545  \begin{itemize}
546   \item \underline{Exchange correlation functional}
547         - approximations for the inhomogeneous electron gas
548         \begin{itemize}
549          \item LDA: $E_{\text{XC}}^{\text{LDA}}[n]=\int \epsilon_{\text{XC}}(n)n(r)d^3r$
550          \item GGA: $E_{\text{XC}}^{\text{GGA}}[n]=\int \epsilon_{\text{XC}}(n,\nabla n)n(r)d^3r$
551         \end{itemize}
552   \item \underline{Plane wave basis set}
553         - approximation of the wavefunction $\Phi_i$ by plane waves $\phi_j$
554 \[
555 \rightarrow
556 \text{Fourier series: } \Phi_i=\sum_{|G+k|<G_{\text{cut}}} c_j^i \phi_j(r), \quad E_{\text{cut}}=\frac{\hbar^2}{2m}G^2_{\text{cut}}
557 \]
558   \item \underline{$k$-point sampling} - $\Gamma$-point only calculations
559   \item \underline{Pseudo potential} 
560         - consider only the valence electrons
561   \item \underline{Code} - VASP 4.6
562  \end{itemize}
563
564  \vspace*{0.2cm}
565
566  MD and structural optimization
567
568  \begin{itemize}
569   \item MD integration: Gear predictor corrector algorithm
570   \item Pressure control: Parrinello-Rahman pressure control
571   \item Structural optimization: Conjugate gradient method
572  \end{itemize}
573
574 \end{slide}
575
576 \begin{slide}
577
578  {\large\bf
579   C and Si self-interstitial point defects in silicon
580  }
581
582  \small
583
584  \vspace*{0.3cm}
585
586 \begin{minipage}{8cm}
587 Procedure:\\[0.3cm]
588   \begin{pspicture}(0,0)(7,5)
589   \rput(3.5,4){\rnode{init}{\psframebox[fillstyle=solid,fillcolor=hb]{
590    \parbox{7cm}{
591    \begin{itemize}
592     \item Creation of c-Si simulation volume
593     \item Periodic boundary conditions
594     \item $T=0\text{ K}$, $p=0\text{ bar}$
595    \end{itemize}
596   }}}}
597 \rput(3.5,2.1){\rnode{insert}{\psframebox{
598  \parbox{7cm}{
599   \begin{center}
600   Insertion of interstitial C/Si atoms
601   \end{center}
602   }}}}
603   \rput(3.5,1){\rnode{cool}{\psframebox[fillstyle=solid,fillcolor=lbb]{
604    \parbox{7cm}{
605    \begin{center}
606    Relaxation / structural energy minimization
607    \end{center}
608   }}}}
609   \ncline[]{->}{init}{insert}
610   \ncline[]{->}{insert}{cool}
611  \end{pspicture}
612 \end{minipage}
613 \begin{minipage}{5cm}
614   \includegraphics[width=5cm]{unit_cell_e.eps}\\
615 \end{minipage}
616
617 \begin{minipage}{9cm}
618  \begin{tabular}{l c c}
619  \hline
620  & size [unit cells] & \# atoms\\
621 \hline
622 VASP & $3\times 3\times 3$ & $216\pm 1$ \\
623 Erhart/Albe & $9\times 9\times 9$ & $5832\pm 1$\\
624 \hline
625  \end{tabular}
626 \end{minipage}
627 \begin{minipage}{4cm}
628 {\color{red}$\bullet$} Tetrahedral\\
629 {\color{green}$\bullet$} Hexagonal\\
630 {\color{yellow}$\bullet$} \hkl<1 0 0> dumbbell\\
631 {\color{magenta}$\bullet$} \hkl<1 1 0> dumbbell\\
632 {\color{cyan}$\bullet$} Bond-centered\\
633 {\color{black}$\bullet$} Vacancy / Substitutional
634 \end{minipage}
635
636 \end{slide}
637
638 \begin{slide}
639
640  \footnotesize
641
642 \begin{minipage}{9.5cm}
643
644  {\large\bf
645   Si self-interstitial point defects in silicon\\
646  }
647
648 \begin{tabular}{l c c c c c}
649 \hline
650  $E_{\text{f}}$ [eV] & \hkl<1 1 0> DB & H & T & \hkl<1 0 0> DB & V \\
651 \hline
652  VASP & \underline{3.39} & 3.42 & 3.77 & 4.41 & 3.63 \\
653  Erhart/Albe & 4.39 & 4.48$^*$ & \underline{3.40} & 5.42 & 3.13 \\
654 \hline
655 \end{tabular}\\[0.2cm]
656
657 \begin{minipage}{4.7cm}
658 \includegraphics[width=4.7cm]{e_kin_si_hex.ps}
659 \end{minipage}
660 \begin{minipage}{4.7cm}
661 \begin{center}
662 {\tiny nearly T $\rightarrow$ T}\\
663 \end{center}
664 \includegraphics[width=4.7cm]{nhex_tet.ps}
665 \end{minipage}\\
666
667 \underline{Hexagonal} \hspace{2pt}
668 \href{../video/si_self_int_hexa.avi}{$\rhd$}\\[0.1cm]
669 \framebox{
670 \begin{minipage}{2.7cm}
671 $E_{\text{f}}^*=4.48\text{ eV}$\\
672 \includegraphics[width=2.7cm]{si_pd_albe/hex_a.eps}
673 \end{minipage}
674 \begin{minipage}{0.4cm}
675 \begin{center}
676 $\Rightarrow$
677 \end{center}
678 \end{minipage}
679 \begin{minipage}{2.7cm}
680 $E_{\text{f}}=3.96\text{ eV}$\\
681 \includegraphics[width=2.8cm]{si_pd_albe/hex.eps}
682 \end{minipage}
683 }
684 \begin{minipage}{2.9cm}
685 \begin{flushright}
686 \underline{Vacancy}\\
687 \includegraphics[width=3.0cm]{si_pd_albe/vac.eps}
688 \end{flushright}
689 \end{minipage}
690
691 \end{minipage}
692 \begin{minipage}{3.5cm}
693
694 \begin{flushright}
695 \underline{\hkl<1 1 0> dumbbell}\\
696 \includegraphics[width=3.0cm]{si_pd_albe/110.eps}\\
697 \underline{Tetrahedral}\\
698 \includegraphics[width=3.0cm]{si_pd_albe/tet.eps}\\
699 \underline{\hkl<1 0 0> dumbbell}\\
700 \includegraphics[width=3.0cm]{si_pd_albe/100.eps}
701 \end{flushright}
702
703 \end{minipage}
704
705 \end{slide}
706
707 \begin{slide}
708
709 \footnotesize
710
711  {\large\bf
712   C interstitial point defects in silicon\\[-0.1cm]
713  }
714
715 \begin{tabular}{l c c c c c c}
716 \hline
717  $E_{\text{f}}$ & T & H & \hkl<1 0 0> DB & \hkl<1 1 0> DB & S & B \\
718 \hline
719  VASP & unstable & unstable & \underline{3.72} & 4.16 & 1.95 & 4.66 \\
720  Erhart/Albe MD & 6.09 & 9.05$^*$ & \underline{3.88} & 5.18 & 0.75 & 5.59$^*$ \\
721 \hline
722 \end{tabular}\\[0.1cm]
723
724 \framebox{
725 \begin{minipage}{2.7cm}
726 \underline{Hexagonal} \hspace{2pt}
727 \href{../video/c_in_si_int_hexa.avi}{$\rhd$}\\
728 $E_{\text{f}}^*=9.05\text{ eV}$\\
729 \includegraphics[width=2.7cm]{c_pd_albe/hex.eps}
730 \end{minipage}
731 \begin{minipage}{0.4cm}
732 \begin{center}
733 $\Rightarrow$
734 \end{center}
735 \end{minipage}
736 \begin{minipage}{2.7cm}
737 \underline{\hkl<1 0 0>}\\
738 $E_{\text{f}}=3.88\text{ eV}$\\
739 \includegraphics[width=2.7cm]{c_pd_albe/100.eps}
740 \end{minipage}
741 }
742 \begin{minipage}{2cm}
743 \hfill
744 \end{minipage}
745 \begin{minipage}{3cm}
746 \begin{flushright}
747 \underline{Tetrahedral}\\
748 \includegraphics[width=3.0cm]{c_pd_albe/tet.eps}
749 \end{flushright}
750 \end{minipage}
751
752 \framebox{
753 \begin{minipage}{2.7cm}
754 \underline{Bond-centered}\\
755 $E_{\text{f}}^*=5.59\text{ eV}$\\
756 \includegraphics[width=2.7cm]{c_pd_albe/bc.eps}
757 \end{minipage}
758 \begin{minipage}{0.4cm}
759 \begin{center}
760 $\Rightarrow$
761 \end{center}
762 \end{minipage}
763 \begin{minipage}{2.7cm}
764 \underline{\hkl<1 1 0> dumbbell}\\
765 $E_{\text{f}}=5.18\text{ eV}$\\
766 \includegraphics[width=2.7cm]{c_pd_albe/110.eps}
767 \end{minipage}
768 }
769 \begin{minipage}{2cm}
770 \hfill
771 \end{minipage}
772 \begin{minipage}{3cm}
773 \begin{flushright}
774 \underline{Substitutional}\\
775 \includegraphics[width=3.0cm]{c_pd_albe/sub.eps}
776 \end{flushright}
777 \end{minipage}
778
779 \end{slide}
780
781 \begin{slide}
782
783 \footnotesize
784
785  {\large\bf\boldmath
786   C \hkl<1 0 0> dumbbell interstitial configuration\\
787  }
788
789 {\tiny
790 \begin{tabular}{l c c c c c c c c}
791 \hline
792  Distances [nm] & $r(1C)$ & $r(2C)$ & $r(3C)$ & $r(12)$ & $r(13)$ & $r(34)$ & $r(23)$ & $r(25)$ \\
793 \hline
794 Erhart/Albe & 0.175 & 0.329 & 0.186 & 0.226 & 0.300 & 0.343 & 0.423 & 0.425 \\
795 VASP & 0.174 & 0.341 & 0.182 & 0.229 & 0.286 & 0.347 & 0.422 & 0.417 \\
796 \hline
797 \end{tabular}\\[0.2cm]
798 \begin{tabular}{l c c c c }
799 \hline
800  Angles [$^{\circ}$] & $\theta_1$ & $\theta_2$ & $\theta_3$ & $\theta_4$ \\
801 \hline
802 Erhart/Albe & 140.2 & 109.9 & 134.4 & 112.8 \\
803 VASP & 130.7 & 114.4 & 146.0 & 107.0 \\
804 \hline
805 \end{tabular}\\[0.2cm]
806 \begin{tabular}{l c c c}
807 \hline
808  Displacements [nm]& $a$ & $b$ & $|a|+|b|$ \\
809 \hline
810 Erhart/Albe & 0.084 & -0.091 & 0.175 \\
811 VASP & 0.109 & -0.065 & 0.174 \\
812 \hline
813 \end{tabular}\\[0.6cm]
814 }
815
816 \begin{minipage}{3.0cm}
817 \begin{center}
818 \underline{Erhart/Albe}
819 \includegraphics[width=3.0cm]{c_pd_albe/100_cmp.eps}
820 \end{center}
821 \end{minipage}
822 \begin{minipage}{3.0cm}
823 \begin{center}
824 \underline{VASP}
825 \includegraphics[width=3.0cm]{c_pd_vasp/100_cmp.eps}
826 \end{center}
827 \end{minipage}\\
828
829 \begin{picture}(0,0)(-185,10)
830 \includegraphics[width=6.8cm]{100-c-si-db_cmp.eps}
831 \end{picture}
832 \begin{picture}(0,0)(-280,-150)
833 \includegraphics[width=3.3cm]{c_pd_vasp/eden.eps}
834 \end{picture}
835
836 \begin{pspicture}(0,0)(0,0)
837 \psellipse[linecolor=green](5.18,5.92)(0.5,0.3)
838 \psellipse[linecolor=red](3.45,5.92)(1.0,0.4)
839 \psellipse[linecolor=blue](2.7,6.92)(0.9,0.2)
840 \psellipse[linecolor=blue](4.65,6.92)(0.9,0.2)
841 \end{pspicture}
842
843 \end{slide}
844
845 \begin{slide}
846
847 \small
848
849 \begin{minipage}{8.5cm}
850
851  {\large\bf
852   Bond-centered interstitial configuration\\[-0.1cm]
853  }
854
855 \begin{minipage}{3.0cm}
856 \includegraphics[width=2.8cm]{c_pd_vasp/bc_2333.eps}\\
857 \end{minipage}
858 \begin{minipage}{5.2cm}
859 \begin{itemize}
860  \item Linear Si-C-Si bond
861  \item Si: one C \& 3 Si neighbours
862  \item Spin polarized calculations
863  \item No saddle point!\\
864        Real local minimum!
865 \end{itemize}
866 \end{minipage}
867
868 \framebox{
869  \tiny
870  \begin{minipage}[t]{6.5cm}
871   \begin{minipage}[t]{1.2cm}
872   {\color{red}Si}\\
873   {\tiny sp$^3$}\\[0.8cm]
874   \underline{${\color{black}\uparrow}$}
875   \underline{${\color{black}\uparrow}$}
876   \underline{${\color{black}\uparrow}$}
877   \underline{${\color{red}\uparrow}$}\\
878   sp$^3$
879   \end{minipage}
880   \begin{minipage}[t]{1.4cm}
881   \begin{center}
882   {\color{red}M}{\color{blue}O}\\[0.8cm]
883   \underline{${\color{blue}\uparrow}{\color{white}\downarrow}$}\\
884   $\sigma_{\text{ab}}$\\[0.5cm]
885   \underline{${\color{red}\uparrow}{\color{blue}\downarrow}$}\\
886   $\sigma_{\text{b}}$
887   \end{center}
888   \end{minipage}
889   \begin{minipage}[t]{1.0cm}
890   \begin{center}
891   {\color{blue}C}\\
892   {\tiny sp}\\[0.2cm]
893   \underline{${\color{white}\uparrow\uparrow}$}
894   \underline{${\color{white}\uparrow\uparrow}$}\\
895   2p\\[0.4cm]
896   \underline{${\color{blue}\uparrow}{\color{blue}\downarrow}$}
897   \underline{${\color{blue}\uparrow}{\color{blue}\downarrow}$}\\
898   sp
899   \end{center}
900   \end{minipage}
901   \begin{minipage}[t]{1.4cm}
902   \begin{center}
903   {\color{blue}M}{\color{green}O}\\[0.8cm]
904   \underline{${\color{blue}\uparrow}{\color{white}\downarrow}$}\\
905   $\sigma_{\text{ab}}$\\[0.5cm]
906   \underline{${\color{green}\uparrow}{\color{blue}\downarrow}$}\\
907   $\sigma_{\text{b}}$
908   \end{center}
909   \end{minipage}
910   \begin{minipage}[t]{1.2cm}
911   \begin{flushright}
912   {\color{green}Si}\\
913   {\tiny sp$^3$}\\[0.8cm]
914   \underline{${\color{green}\uparrow}$}
915   \underline{${\color{black}\uparrow}$}
916   \underline{${\color{black}\uparrow}$}
917   \underline{${\color{black}\uparrow}$}\\
918   sp$^3$
919   \end{flushright}
920   \end{minipage}
921  \end{minipage}
922 }\\[0.1cm]
923
924 \framebox{
925 \begin{minipage}{4.5cm}
926 \includegraphics[width=4cm]{c_100_mig_vasp/im_spin_diff.eps}
927 \end{minipage}
928 \begin{minipage}{3.5cm}
929 {\color{gray}$\bullet$} Spin up\\
930 {\color{green}$\bullet$} Spin down\\
931 {\color{blue}$\bullet$} Resulting spin up\\
932 {\color{yellow}$\bullet$} Si atoms\\
933 {\color{red}$\bullet$} C atom
934 \end{minipage}
935 }
936
937 \end{minipage}
938 \begin{minipage}{4.2cm}
939 \begin{flushright}
940 \includegraphics[width=4.3cm]{c_pd_vasp/bc_2333_ksl.ps}\\
941 {\color{green}$\Box$} {\tiny unoccupied}\\
942 {\color{red}$\bullet$} {\tiny occupied}
943 \end{flushright}
944 \end{minipage}
945
946 \end{slide}
947
948 \begin{slide}
949
950  {\large\bf\boldmath
951   Migration of the C \hkl<1 0 0> dumbbell interstitial
952  }
953
954 \scriptsize
955
956  {\small Investigated pathways}
957
958 \begin{minipage}{8.5cm}
959 \begin{minipage}{8.3cm}
960 \underline{\hkl<0 0 -1> $\rightarrow$ \hkl<0 0 1>}\\
961 \begin{minipage}{2.4cm}
962 \includegraphics[width=2.4cm]{c_pd_vasp/100_2333.eps}
963 \end{minipage}
964 \begin{minipage}{0.4cm}
965 $\rightarrow$
966 \end{minipage}
967 \begin{minipage}{2.4cm}
968 \includegraphics[width=2.4cm]{c_pd_vasp/bc_2333.eps}
969 \end{minipage}
970 \begin{minipage}{0.4cm}
971 $\rightarrow$
972 \end{minipage}
973 \begin{minipage}{2.4cm}
974 \includegraphics[width=2.4cm]{c_pd_vasp/100_next_2333.eps}
975 \end{minipage}
976 \end{minipage}\\
977 \begin{minipage}{8.3cm}
978 \underline{\hkl<0 0 -1> $\rightarrow$ \hkl<0 -1 0>}\\
979 \begin{minipage}{2.4cm}
980 \includegraphics[width=2.4cm]{c_pd_vasp/100_2333.eps}
981 \end{minipage}
982 \begin{minipage}{0.4cm}
983 $\rightarrow$
984 \end{minipage}
985 \begin{minipage}{2.4cm}
986 \includegraphics[width=2.4cm]{c_pd_vasp/00-1-0-10_2333.eps}
987 \end{minipage}
988 \begin{minipage}{0.4cm}
989 $\rightarrow$
990 \end{minipage}
991 \begin{minipage}{2.4cm}
992 \includegraphics[width=2.4cm]{c_pd_vasp/0-10_2333.eps}
993 \end{minipage}
994 \end{minipage}\\
995 \begin{minipage}{8.3cm}
996 \underline{\hkl<0 0 -1> $\rightarrow$ \hkl<0 -1 0> (in place)}\\
997 \begin{minipage}{2.4cm}
998 \includegraphics[width=2.4cm]{c_pd_vasp/100_2333.eps}
999 \end{minipage}
1000 \begin{minipage}{0.4cm}
1001 $\rightarrow$
1002 \end{minipage}
1003 \begin{minipage}{2.4cm}
1004 \includegraphics[width=2.4cm]{c_pd_vasp/00-1_ip0-10_2333.eps}
1005 \end{minipage}
1006 \begin{minipage}{0.4cm}
1007 $\rightarrow$
1008 \end{minipage}
1009 \begin{minipage}{2.4cm}
1010 \includegraphics[width=2.4cm]{c_pd_vasp/0-10_ip_2333.eps}
1011 \end{minipage}
1012 \end{minipage}
1013 \end{minipage}
1014 \framebox{
1015 \begin{minipage}{4.2cm}
1016  {\small Constrained relaxation\\
1017          technique (CRT) method}\\
1018 \includegraphics[width=4cm]{crt_orig.eps}
1019 \begin{itemize}
1020  \item Constrain diffusing atom
1021  \item Static constraints 
1022 \end{itemize}
1023 \vspace*{0.3cm}
1024  {\small Modifications}\\
1025 \includegraphics[width=4cm]{crt_mod.eps}
1026 \begin{itemize}
1027  \item Constrain all atoms
1028  \item Update individual\\
1029        constraints
1030 \end{itemize}
1031 \end{minipage}
1032 }
1033
1034 \end{slide}
1035
1036 \begin{slide}
1037
1038  {\large\bf\boldmath
1039   Migration of the C \hkl<1 0 0> dumbbell interstitial
1040  }
1041
1042 \scriptsize
1043
1044 \framebox{
1045 \begin{minipage}{5.9cm}
1046 \begin{flushleft}
1047 \includegraphics[width=5.8cm]{im_00-1_nosym_sp_fullct_thesis.ps}\\[0.45cm]
1048 \end{flushleft}
1049 \begin{center}
1050 \begin{picture}(0,0)(60,0)
1051 \includegraphics[width=1cm]{vasp_mig/00-1.eps}
1052 \end{picture}
1053 \begin{picture}(0,0)(-5,0)
1054 \includegraphics[width=1cm]{vasp_mig/bc_00-1_sp.eps}
1055 \end{picture}
1056 \begin{picture}(0,0)(-55,0)
1057 \includegraphics[width=1cm]{vasp_mig/bc.eps}
1058 \end{picture}
1059 \begin{picture}(0,0)(12.5,10)
1060 \includegraphics[width=1cm]{110_arrow.eps}
1061 \end{picture}
1062 \begin{picture}(0,0)(90,0)
1063 \includegraphics[height=0.9cm]{001_arrow.eps}
1064 \end{picture}
1065 \end{center}
1066 \vspace*{0.35cm}
1067 \end{minipage}
1068 }
1069 \begin{minipage}{0.3cm}
1070 \hfill
1071 \end{minipage}
1072 \framebox{
1073 \begin{minipage}{5.9cm}
1074 \begin{flushright}
1075 \includegraphics[width=5.9cm]{vasp_mig/00-1_0-10_nosym_sp_fullct.ps}\\[0.5cm]
1076 \end{flushright}
1077 \begin{center}
1078 \begin{picture}(0,0)(60,0)
1079 \includegraphics[width=1cm]{vasp_mig/00-1_a.eps}
1080 \end{picture}
1081 \begin{picture}(0,0)(5,0)
1082 \includegraphics[width=1cm]{vasp_mig/00-1_0-10_sp.eps}
1083 \end{picture}
1084 \begin{picture}(0,0)(-55,0)
1085 \includegraphics[width=1cm]{vasp_mig/0-10.eps}
1086 \end{picture}
1087 \begin{picture}(0,0)(12.5,10)
1088 \includegraphics[width=1cm]{100_arrow.eps}
1089 \end{picture}
1090 \begin{picture}(0,0)(90,0)
1091 \includegraphics[height=0.9cm]{001_arrow.eps}
1092 \end{picture}
1093 \end{center}
1094 \vspace*{0.3cm}
1095 \end{minipage}\\
1096 }
1097
1098 \vspace*{0.05cm}
1099
1100 \framebox{
1101 \begin{minipage}{5.9cm}
1102 \begin{flushleft}
1103 \includegraphics[width=5.9cm]{vasp_mig/00-1_ip0-10_nosym_sp_fullct.ps}\\[0.6cm]
1104 \end{flushleft}
1105 \begin{center}
1106 \begin{picture}(0,0)(60,0)
1107 \includegraphics[width=0.9cm]{vasp_mig/00-1_b.eps}
1108 \end{picture}
1109 \begin{picture}(0,0)(10,0)
1110 \includegraphics[width=0.9cm]{vasp_mig/00-1_ip0-10_sp.eps}
1111 \end{picture}
1112 \begin{picture}(0,0)(-60,0)
1113 \includegraphics[width=0.9cm]{vasp_mig/0-10_b.eps}
1114 \end{picture}
1115 \begin{picture}(0,0)(12.5,10)
1116 \includegraphics[width=1cm]{100_arrow.eps}
1117 \end{picture}
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1120 \end{picture}
1121 \end{center}
1122 \vspace*{0.3cm}
1123 \end{minipage}
1124 }
1125 \begin{minipage}{0.3cm}
1126 \hfill
1127 \end{minipage}
1128 \begin{minipage}{6.5cm}
1129 VASP results
1130 \begin{itemize}
1131  \item Energetically most favorable path
1132        \begin{itemize}
1133         \item Path 2
1134         \item Activation energy: $\approx$ 0.9 eV 
1135         \item Experimental values: 0.73 ... 0.87 eV
1136        \end{itemize}
1137        $\Rightarrow$ {\color{blue}Diffusion} path identified!
1138  \item Reorientation (path 3)
1139        \begin{itemize}
1140         \item More likely composed of two consecutive steps of type 2
1141         \item Experimental values: 0.77 ... 0.88 eV
1142        \end{itemize}
1143        $\Rightarrow$ {\color{blue}Reorientation} transition identified!
1144 \end{itemize}
1145 \end{minipage}
1146
1147 \end{slide}
1148
1149 \begin{slide}
1150
1151  {\large\bf\boldmath
1152   Migration of the C \hkl<1 0 0> dumbbell interstitial
1153  }
1154
1155 \scriptsize
1156
1157 \begin{minipage}{6.5cm}
1158
1159 \framebox{
1160 \begin{minipage}{5.9cm}
1161 \begin{flushleft}
1162 \includegraphics[width=5.9cm]{bc_00-1.ps}\\[2.35cm]
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1164 \begin{center}
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1204 \end{center}
1205 \end{minipage}
1206 }\\[0.1cm]
1207
1208 \begin{minipage}{5.9cm}
1209 Erhart/Albe results
1210 \begin{itemize}
1211  \item Lowest activation energy: $\approx$ 2.2 eV
1212  \item 2.4 times higher than VASP
1213  \item Different pathway
1214  \item Transition minima ($\rightarrow$ \hkl<1 1 0> dumbbell)
1215 \end{itemize}
1216 \end{minipage}
1217
1218 \end{minipage}
1219 \begin{minipage}{6.5cm}
1220
1221 \framebox{
1222 \begin{minipage}{5.9cm}
1223 \begin{flushright}
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1226 \begin{center}
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1246 \vspace{0.2cm}
1247 \end{minipage}
1248 }\\[0.2cm]
1249
1250 \framebox{
1251 \begin{minipage}{5.9cm}
1252 \includegraphics[width=5.9cm]{00-1_ip0-10.ps}
1253 \end{minipage}
1254 }
1255
1256 \end{minipage}
1257
1258 \end{slide}
1259
1260 \begin{slide}
1261
1262  {\large\bf\boldmath
1263   Migration involving the C \hkl<1 1 0> dumbbell interstitial
1264  }
1265
1266 \scriptsize
1267
1268
1269 \end{slide}
1270
1271 \begin{slide}
1272
1273  {\large\bf\boldmath
1274   Combinations of point defects
1275  }
1276
1277 \scriptsize
1278
1279
1280 \end{slide}
1281
1282 \begin{slide}
1283
1284  {\large\bf
1285   Silicon carbide precipitation simulations
1286  }
1287
1288  \small
1289
1290 \end{slide}
1291
1292 \begin{slide}
1293
1294  {\large\bf
1295   Investigation of a silicon carbide precipitate in silicon
1296  }
1297
1298  \small
1299
1300 \end{slide}
1301
1302 \end{document}