From a26586e1fd32745c018e4111b98b34e628aaf245 Mon Sep 17 00:00:00 2001 From: hackbard Date: Wed, 30 Apr 2008 15:38:38 +0200 Subject: [PATCH] posic publications security checkin --- posic/publications/Makefile | 18 ++++ posic/publications/dpg2008_abstract.tex | 54 ++++++++++ posic/publications/emrs2008_abstract.tex | 58 +++++++++++ posic/publications/emrs2008_full.tex | 124 +++++++++++++++++++++++ 4 files changed, 254 insertions(+) create mode 100644 posic/publications/Makefile create mode 100644 posic/publications/dpg2008_abstract.tex create mode 100644 posic/publications/emrs2008_abstract.tex create mode 100644 posic/publications/emrs2008_full.tex diff --git a/posic/publications/Makefile b/posic/publications/Makefile new file mode 100644 index 0000000..11c00c5 --- /dev/null +++ b/posic/publications/Makefile @@ -0,0 +1,18 @@ +# Makefile +LATEX = latex +DVIPDF = dvipdf + +SRC := $(shell ls *.tex) +PDF = $(SRC:%.tex=%.pdf) + +all: $(PDF) + +%.dvi: %.tex + $(LATEX) $< $@ + $(LATEX) $< $@ + +%.pdf: %.dvi + $(DVIPDF) $< $@ + +clean: + rm -f *.log *.aux diff --git a/posic/publications/dpg2008_abstract.tex b/posic/publications/dpg2008_abstract.tex new file mode 100644 index 0000000..5856e1c --- /dev/null +++ b/posic/publications/dpg2008_abstract.tex @@ -0,0 +1,54 @@ +\pdfoutput=0 +\documentclass[a4paper,11pt]{article} +\usepackage[activate]{pdfcprot} +\usepackage{verbatim} +\usepackage{a4} +\usepackage{a4wide} +\usepackage[german]{babel} +\usepackage[latin1]{inputenc} +\usepackage[T1]{fontenc} +\usepackage{amsmath} +\usepackage{ae} +\usepackage{aecompl} +\usepackage[dvips]{graphicx} +\graphicspath{{./img/}} +\usepackage{color} +\usepackage{pstricks} +\usepackage{pst-node} +\usepackage{rotating} + +\setlength{\headheight}{0mm} \setlength{\headsep}{0mm} +\setlength{\topskip}{-10mm} \setlength{\textwidth}{17cm} +\setlength{\oddsidemargin}{-10mm} +\setlength{\evensidemargin}{-10mm} \setlength{\topmargin}{-1cm} +\setlength{\textheight}{26cm} \setlength{\headsep}{0cm} + +\begin{document} + +% header +\begin{center} + {\LARGE {\bf Molecular dynamics simulation study + of the silicon carbide precipitation process}\\} + \vspace{16pt} + \textsc{\Large \underline{F. Zirkelbach}$^1$, J. K. N. Lindner$^1$, + K. Nordlund$^2$, B. Stritzker$^1$}\\ + \vspace{16pt} + $^1$ Experimentalphysik IV, Institut f"ur Physik, Universit"at Augsburg,\\ + Universit"atsstr. 1, D-86135 Augsburg, Germany\\ + \vspace{16pt} + $^2$ Accelerator Laboratory, Department of Physical Sciences, + University of Helsinki,\\ + Pietari Kalmink. 2, 00014 Helsinki, Finland\\ +\end{center} + +\vspace{24pt} + +\section*{Abstract} +The precipitation process of silicon carbide in heavily carbon doped silicon is not yet understood for the most part. +High resolution transmission electron microscopy indicates that in a first step carbon atoms form $C-Si$ dumbbells on regular $Si$ lattice sites which agglomerate into large clusters. +In a second step, when the cluster size reaches a radius of a few $nm$, the high interfacial energy due to the $SiC$/$Si$ lattice misfit of almost $20 \, \%$ is overcome and the precipitation occurs. +A molecular dynamics simulation approach is used to gain information of the precipitation process on the atomic level. +A newly parametrized Tersoff like bond-order potential is used to model the system appropriately. +The present work discusses the first results gained by the molecular dynamics simulation. + +\end{document} diff --git a/posic/publications/emrs2008_abstract.tex b/posic/publications/emrs2008_abstract.tex new file mode 100644 index 0000000..e7cc4fe --- /dev/null +++ b/posic/publications/emrs2008_abstract.tex @@ -0,0 +1,58 @@ +\pdfoutput=0 +\documentclass[a4paper,11pt]{article} +\usepackage[activate]{pdfcprot} +\usepackage{verbatim} +\usepackage{a4} +\usepackage{a4wide} +\usepackage[german]{babel} +\usepackage[latin1]{inputenc} +\usepackage[T1]{fontenc} +\usepackage{amsmath} +\usepackage{ae} +\usepackage{aecompl} +\usepackage[dvips]{graphicx} +\graphicspath{{./img/}} +\usepackage{color} +\usepackage{pstricks} +\usepackage{pst-node} +\usepackage{rotating} + +\setlength{\headheight}{0mm} \setlength{\headsep}{0mm} +\setlength{\topskip}{-10mm} \setlength{\textwidth}{17cm} +\setlength{\oddsidemargin}{-10mm} +\setlength{\evensidemargin}{-10mm} \setlength{\topmargin}{-1cm} +\setlength{\textheight}{26cm} \setlength{\headsep}{0cm} + +\begin{document} + +% header +\begin{center} + {\LARGE {\bf Molecular dynamics simulation + of defect formation and precipitation + in heavily carbon doped silicon. + }\\} + \vspace{16pt} + \textsc{\Large \underline{F. Zirkelbach}$^1$, J. K. N. Lindner$^1$, + K. Nordlund$^2$, B. Stritzker$^1$}\\ + \vspace{16pt} + $^1$ Experimentalphysik IV, Institut f"ur Physik, Universit"at Augsburg,\\ + Universit"atsstr. 1, D-86135 Augsburg, Germany\\ + \vspace{16pt} + $^2$ Accelerator Laboratory, Department of Physical Sciences, + University of Helsinki,\\ + Pietari Kalmink. 2, 00014 Helsinki, Finland\\ +\end{center} + +\vspace{24pt} + +\section*{Abstract} +The precipitation process of silicon carbide in heavily carbon doped silicon is not yet understood for the most part. +High resolution transmission electron microscopy indicates that in a first step carbon atoms form $C-Si$ dumbbells on regular $Si$ lattice sites which agglomerate into large clusters. +In a second step, when the cluster size reaches a radius of a few $nm$, the high interfacial energy due to the $SiC$/$Si$ lattice misfit of almost $20 \, \%$ is overcome and the precipitation occurs. +By simulation details of the precipitation process can be obtained on the atomic level. +A newly parametrized Tersoff like bond-order potential is used to model the system appropriately. +First results gained by molecular dynamics simulations using this potential are presented. +The influence of the amount and placement of inserted carbon atoms on the defect formation and structural changes is discussed. +Furthermore a minimal carbon concentration necessary for precipitation is examined by simulation. + +\end{document} diff --git a/posic/publications/emrs2008_full.tex b/posic/publications/emrs2008_full.tex new file mode 100644 index 0000000..5ee36aa --- /dev/null +++ b/posic/publications/emrs2008_full.tex @@ -0,0 +1,124 @@ +\pdfoutput=0 +\documentclass[a4paper,11pt]{article} +\usepackage[activate]{pdfcprot} +\usepackage{verbatim} +\usepackage{a4} +\usepackage{a4wide} +\usepackage[german]{babel} +\usepackage[latin1]{inputenc} +\usepackage[T1]{fontenc} +\usepackage{amsmath} +\usepackage{ae} +\usepackage{aecompl} +\usepackage[dvips]{graphicx} +\graphicspath{{./img/}} +\usepackage{color} +\usepackage{pstricks} +\usepackage{pst-node} +\usepackage{rotating} + +\setlength{\headheight}{0mm} \setlength{\headsep}{0mm} +\setlength{\topskip}{-10mm} \setlength{\textwidth}{17cm} +\setlength{\oddsidemargin}{-10mm} +\setlength{\evensidemargin}{-10mm} \setlength{\topmargin}{-1cm} +\setlength{\textheight}{26cm} \setlength{\headsep}{0cm} + +\begin{document} + +% header +\begin{center} + {\LARGE {\bf Molecular dynamics simulation + of defect formation and precipitation + in heavily carbon doped silicon + }\\} + \vspace{16pt} + \textsc{\Large F. Zirkelbach$^1$, J. K. N. Lindner$^1$, + K. Nordlund$^2$, B. Stritzker$^1$}\\ + \vspace{16pt} + $^1$ Experimentalphysik IV, Institut f"ur Physik, Universit"at Augsburg,\\ + Universit"atsstr. 1, D-86135 Augsburg, Germany\\ + \vspace{16pt} + $^2$ Accelerator Laboratory, Department of Physical Sciences, + University of Helsinki,\\ + Pietari Kalmink. 2, 00014 Helsinki, Finland\\ + \vspace{16pt} + {\scriptsize Corresponding author: Frank Zirkelbach + } +\end{center} + +\vspace{24pt} + +\section*{Abstract} +The precipitation process of silicon carbide in heavily carbon doped silicon is not yet understood for the most part. +High resolution transmission electron microscopy indicates that in a first step carbon atoms form $C-Si$ dumbbells on regular $Si$ lattice sites which agglomerate into large clusters. +In a second step, when the cluster size reaches a radius of a few $nm$, the high interfacial energy due to the $SiC$/$Si$ lattice misfit of almost $20 \, \%$ is overcome and the precipitation occurs. +By simulation details of the precipitation process can be obtained on the atomic level. +A newly parametrized Tersoff like bond-order potential is used to model the system appropriately. +First results gained by molecular dynamics simulations using this potential are presented. +The influence of the amount and placement of inserted carbon atoms on the defect formation and structural changes is discussed. +Furthermore a minimal carbon concentration necessary for precipitation is examined by simulation. +\\\\ +{\bf Keywords:} Silicon carbide, Nucleation, Molecular dynamics simulation. + +\section*{Introduction} +Understanding the precipitation process of cubic silicon carbide (3C-SiC) in heavily carbon doped silicon (Si) will enable significant technological progress in thin film formation of an important wide band gap semiconductor material. +On the other hand it will likewise offer perspectives for processes which rely upon prevention of precipitation processes, e.g. for the fabrication of strained silicon. + +Epitaxial growth of 3C-SiC films is achieved either by ion implantation or chemical vapour deposition techniques. +Surface effects dominate the CVD process while for the implantation process carbon is introduced into bulk silicon. +This work tries to realize conditions which hold for the ion implantation process. + +First of all a suitable model is considered. +After that the realization by simulation is discussed. +First results gained by simulation are presented in a next step. +Finally these results are outlined and conclusions are infered. + +\section*{Supposed conversion mechanism} +Silicon (Si) nucleates in diamond structure. +Contains of two fcc lattices, on displaced one quarter of volume diagonal compared to the first. +3C-SiC nucleates in zincblende structure where the shifted fcc lattice sites are composed of carbon atoms. +The length of four lattice constants of Si is approximately equal to the length of five 3C-SiC lattice constants ($4a_{Si}\approx 5a_{3C-SiC}$), which means that there is a lattice misfit of almost 20\%. +Due to this the silicon density of 3C-SiC is slightly lower than the one of silicon. + +There is a supposed conversion mechanism of heavily carbon doped Si into SiC. +Fig. 1 schematically displays the mechanism. +As indicated by high resolution transmission microscopy \ref{hrem_ind} introduced carbon atoms (red dots) form C-Si dumbbells on regular Si (black dots) lattice sites. +The dumbbells agglomerate int large clusters, so called embryos. +Finally, when the cluster size reaches a critical radius of 2 to 4 nm, the high interfacial energy due to the lattice misfit is overcome and the precipitation occurs. +Due to the slightly lower silicon density of 3C-SiC residual silicon atoms exist. +The residual atoms will most probably end up as self interstitials in the silicon matrix since there is more space than in 3C-SiC. + +Taking this into account, it is important to understand both, the configuration and dynamics of carbon interstitials in silicon and silicon self interstitials. +Additionaly the influence of interstitials on atomic diffusion is investigated. + +\section*{Simulation} +A molecular dynamics simulation approach is used to examine the steps involved in the precipitation process. +For integrating the equations of motion the velocity verlet algorithm \ref{} with a timestep of 1 fs is deployed. +The interaction of the silicon and carbon atoms is realized by a newly parametrized Tersoff like bond order potential \ref{}. +Since temperature and pressure of the system is kept constant in experiment the isothermal-isobaric NPT ensemble is chosen for the simulation. +Coupling to the heat bath is achieved by the Berendsen thermostat \ref{} with a time constant $\tau_T=100\, fs$. +The pressure is scaled by the Berendsen barostat \ref{} again using a timeconstant of $\tau_P=100\, fs$ and a bulk modulus of $100\, GPa$ for silicon. +To exclude surface effects periodic boundary conditions are applied. +\\\\ +To investigate the intesrtitial configurations of C and Si in Si, a simulation volume of 9 silicon unit cells is each direction used. +The temperature is set to $T=0\, K$. +The insertion positions are illustrated in Fig 2. +In separated simulation runs a carbon and a silicon atom respectively is inserted at the tetrahedral $(0,0,0)$ (red), hexagonal $(-1/8,-1/8,1/8)$ (green), supposed dumbbell $(-1/8,-1/8)$ (purple) and at random positions (in units of the silicon lattice constant) where the origin is located in the middle of the unit cell. +In order to avoid too high kinetic energies in the case of the dumbbell configuration the nearest silicon neighbour atom is shifted to $(-1/4,-1/4,-1/4)$ (dashed border). +The introduced kinetic energy is scaled out by a relaxation time of $2\, ps$. +\\\\ +The same volume is used to investigate diffusion. +A certain amount of silicon atoms are inserted at random positions in a centered region of $11 \, \AA$ in each direction. +The insertion is taking place step by step in order to maintain a constant system temeprature. +Finally a carbon atom is inserted at a random position in the unit cell located in the middle of the simulation volume. +The simulation continues for another $30\, ps$. +\\\\ +Simulation runs /unt + + + +\section*{Results} + +\section*{Conclusion} + +\end{document} -- 2.20.1