X-Git-Url: https://hackdaworld.org/gitweb/?p=lectures%2Flatex.git;a=blobdiff_plain;f=posic%2Fthesis%2Fdefects.tex;h=a69cfbb1efce4a7c3bb3468231c7b352b45efda4;hp=f1d6d7f510c2a80f7fefa848cdf6d10d6ad10098;hb=5c34f34459cff1df7493614a014d1e594f47a9b6;hpb=0034511d32ceadc7572f9d277fdd690f64c5c507

diff --git a/posic/thesis/defects.tex b/posic/thesis/defects.tex
index f1d6d7f..a69cfbb 100644
--- a/posic/thesis/defects.tex
+++ b/posic/thesis/defects.tex
@@ -18,7 +18,7 @@ Respective results allow to draw conclusions concerning the SiC precipitation in
 
 For investigating the \si{} structures a Si atom is inserted or removed according to Fig. \ref{fig:basics:ins_pos} of section \ref{section:basics:defects}.
 The formation energies of \si{} configurations are listed in Table \ref{tab:defects:si_self} for both methods used in this work as well as results obtained by other {\em ab initio} studies \cite{al-mushadani03,leung99}.
-\begin{table}[t]
+\begin{table}[tp]
 \begin{center}
 \begin{tabular}{l c c c c c}
 \hline
@@ -39,7 +39,7 @@ Ref. \cite{leung99} & 3.31 & 3.31 & 3.43 & - & - \\
 \caption[Formation energies of Si self-interstitials in crystalline Si determined by classical potential MD and DFT calculations.]{Formation energies of Si self-interstitials in crystalline Si determined by classical potential MD and DFT calculations. The formation energies are given in eV. T denotes the tetrahedral and H the hexagonal interstitial configuration. V corresponds to the vacancy configuration. Dumbbell configurations are abbreviated by DB. Formation energies for unstable configurations are marked by an asterisk and determined by using the low kinetic energy configuration shortly before the relaxation into the more favorable configuration starts.}
 \label{tab:defects:si_self}
 \end{table}
-\begin{figure}[t]
+\begin{figure}[tp]
 \begin{center}
 \begin{flushleft}
 \begin{minipage}{5cm}
@@ -107,7 +107,7 @@ The \si{} atom then begins to slowly move towards an energetically more favorabl
 The formation energy of \unit[3.96]{eV} for this type of interstitial is equal to the result for the hexagonal one in the original work \cite{albe_sic_pot}.
 Obviously the authors did not carefully check the relaxed results assuming a hexagonal configuration.
 In Fig. \ref{fig:defects:kin_si_hex} the relaxation process is shown on the basis of the kinetic energy plot.
-\begin{figure}[t]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{e_kin_si_hex.ps}
 \end{center}
@@ -120,7 +120,7 @@ In fact, the same type of interstitial arises using random insertions.
 In addition, variations exist, in which the displacement is only along two \hkl<1 0 0> axes ($E_\text{f}=3.8\,\text{eV}$) or along a single \hkl<1 0 0> axes ($E_\text{f}=3.6\,\text{eV}$) successively approximating the tetdrahedral configuration and formation energy.
 The existence of these local minima located near the tetrahedral configuration seems to be an artifact of the analytical potential without physical authenticity revealing fundamental problems of analytical potential models for describing defect structures.
 However, the energy barrier is small.
-\begin{figure}[!ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{nhex_tet.ps}
 \end{center}
@@ -145,8 +145,6 @@ The length of these bonds are, however, close to the cut-off range and thus are
 The same applies to the bonds between the interstitial and the upper two atoms in the \si{} \hkl<1 1 0> DB configuration.
 A more detailed description of the chemical bonding is achieved through quantum-mechanical calculations by investigating the accumulation of negative charge between the nuclei.
 
-%\clearpage{}
-
 \section{Carbon point defects in silicon}
 
 \subsection{Defect structures in a nutshell}
@@ -158,7 +156,7 @@ Again, the displayed structures are the results obtained by the classical potent
 The type of reservoir of the C impurity to determine the formation energy of the defect is chosen to be SiC.
 This is consistent with the methods used in the articles \cite{tersoff90,dal_pino93}, which the results are compared to in the following.
 Hence, the chemical potential of Si and C is determined by the cohesive energy of Si and SiC as discussed in section \ref{section:basics:defects}.
-\begin{table}[t]
+\begin{table}[tp]
 \begin{center}
 \begin{tabular}{l c c c c c c}
 \hline
@@ -178,7 +176,7 @@ Hence, the chemical potential of Si and C is determined by the cohesive energy o
 \caption[Formation energies of C point defects in c-Si determined by classical potential MD and DFT calculations.]{Formation energies of C point defects in c-Si determined by classical potential MD and DFT calculations. The formation energies are given in eV. T denotes the tetrahedral, H the hexagonal and BC the bond-centered interstitial configuration. S corresponds to the substitutional interstitial configuration. The dumbbell configurations are abbreviated by DB.  Formation energies for unstable configurations are marked by an asterisk and are determined by using the low kinetic energy configuration shortly before the relaxation into the more favorable configuration starts.}
 \label{tab:defects:c_ints}
 \end{table}
-\begin{figure}[t]
+\begin{figure}[tp]
 \begin{center}
 \begin{flushleft}
 \begin{minipage}{4cm}
@@ -297,14 +295,14 @@ The structure was initially suspected by IR local vibrational mode absorption \c
 
 Fig. \ref{fig:defects:100db_cmp} schematically shows the \ci{} \hkl<1 0 0> DB structure and Table \ref{tab:defects:100db_cmp} lists the details of the atomic displacements, distances and bond angles obtained by classical potential and quantum-mechanical calculations.
 For comparison, the obtained structures for both methods are visualized in Fig. \ref{fig:defects:100db_vis_cmp}.
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=12cm]{100-c-si-db_cmp.eps}
 \end{center}
 \caption[Sketch of the \ci{} \hkl<1 0 0> dumbbell structure.]{Sketch of the \ci{} \hkl<1 0 0> dumbbell structure. Atomic displacements, distances and bond angles are listed in Table \ref{tab:defects:100db_cmp}.}
 \label{fig:defects:100db_cmp}
 \end{figure}
-\begin{table}[ht]
+\begin{table}[tp]
 \begin{center}
 Displacements\\
 \begin{tabular}{l c c c c c c c c c}
@@ -348,7 +346,7 @@ Angles\\
 \caption[Atomic displacements, distances and bond angles of the \ci{} \hkl<1 0 0> DB structure obtained by {\textsc posic} and {\textsc vasp} calculations.]{Atomic displacements, distances and bond angles of the \ci{} \hkl<1 0 0> DB structure obtained by {\textsc posic} and {\textsc vasp} calculations. The displacements and distances are given in nm and the angles are given in degrees. Displacements, distances and angles are schematically displayed in Fig. \ref{fig:defects:100db_cmp}. In addition, the equilibrium lattice constant for crystalline Si is listed.}
 \label{tab:defects:100db_cmp}
 \end{table}
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \begin{minipage}{6cm}
 \begin{center}
@@ -366,7 +364,7 @@ Angles\\
 \caption{Comparison of the \ci{} \hkl<1 0 0> DB structures obtained by {\textsc posic} and {\textsc vasp} calculations.}
 \label{fig:defects:100db_vis_cmp}
 \end{figure}
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[height=10cm]{c_pd_vasp/eden.eps}
 \includegraphics[height=12cm]{c_pd_vasp/100_2333_ksl.ps}
@@ -400,7 +398,7 @@ However, strictly speaking, the Kohn-Sham levels and orbitals do not have a dire
 \subsection{Bond-centered interstitial configuration}
 \label{subsection:bc}
 
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \begin{minipage}{8cm}
 \includegraphics[width=8cm]{c_pd_vasp/bc_2333.eps}\\
@@ -433,8 +431,6 @@ The blue torus, which reinforces the assumption of the $p$ orbital, illustrates
 In addition, the energy level diagram shows a net amount of two spin up electrons.
 % todo smaller images, therefore add mo image
 
-\clearpage{}
-
 % todo migration of \si{}!
 
 \section{Migration of the carbon interstitial}
@@ -444,7 +440,7 @@ A measure for the mobility of interstitial C is the activation energy necessary
 The stable defect geometries have been discussed in the previous subsection.
 In the following, the problem of interstitial C migration in Si is considered.
 Since the \ci{} \hkl<1 0 0> DB is the most probable, hence, most important configuration, the migration of this defect atom from one site of the Si host lattice to a neighboring site is in the focus of investigation.
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \begin{minipage}{15cm}
 \underline{\hkl<0 0 -1> $\rightarrow$ \hkl<0 0 1>}\\
@@ -525,7 +521,7 @@ The bond to the face-centered Si atom at the bottom of the unit cell breaks and
 
 \subsection{Migration paths obtained by first-principles calculations}
 
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=13cm]{im_00-1_nosym_sp_fullct_thesis.ps}\\[1.5cm]
 \begin{picture}(0,0)(150,0)
@@ -552,7 +548,7 @@ To reach the BC configuration, which is \unit[0.94]{eV} higher in energy than th
 This amount of energy is needed to break the bond of the C atom to the Si atom at the bottom left.
 In a second process \unit[0.25]{eV} of energy are needed for the system to revert into a \hkl<1 0 0> configuration.
 
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{00-1_0-10_vasp_s.ps}
 %\includegraphics[width=13cm]{vasp_mig/00-1_0-10_nosym_sp_fullct.ps}\\[1.6cm]
@@ -579,7 +575,7 @@ In a second process \unit[0.25]{eV} of energy are needed for the system to rever
 Fig. \ref{fig:defects:00-1_0-10_mig} shows the migration barrier and structures of the \ci{} \hkl<0 0 -1> to \hkl<0 -1 0> DB transition.
 The resulting migration barrier of approximately \unit[0.9]{eV} is very close to the experimentally obtained values of \unit[0.70]{eV} \cite{lindner06}, \unit[0.73]{eV} \cite{song90} and \unit[0.87]{eV} \cite{tipping87}.
 
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=13cm]{vasp_mig/00-1_ip0-10_nosym_sp_fullct.ps}\\[1.8cm]
 \begin{picture}(0,0)(140,0)
@@ -612,7 +608,7 @@ Slightly increased values compared to experiment might be due to the tightend co
 Nevertheless, the theoretical description performed in this work is improved compared to a former study \cite{capaz94}, which underestimates the experimental value by \unit[35]{\%}.
 In addition, it is finally shown that the BC configuration, for which spin polarized calculations are necessary, constitutes a real local minimum instead of a saddle point configuration due to the presence of restoring forces for displacements in migration direction.
 
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{vasp_mig/110_mig_vasp.ps}
 %\begin{picture}(0,0)(140,0)
@@ -651,7 +647,7 @@ For this reason, the assumption that C diffusion and reorientation is achieved b
 %Due to applying updated constraints on all atoms the obtained migration barriers and pathes might be overestimated and misguided.
 %To reinforce the applicability of the employed technique the obtained activation energies and migration pathes for the \hkl<0 0 -1> to \hkl<0 -1 0> transition are compared to two further migration calculations, which do not update the constrainted direction and which only apply updated constraints on three selected atoms, that is the diffusing C atom and the Si dumbbell pair in the initial and final configuration.
 %Results are presented in figure \ref{fig:defects:00-1_0-10_cmp}.
-%\begin{figure}[ht]
+%\begin{figure}[tp]
 %\begin{center}
 %\includegraphics[width=13cm]{vasp_mig/00-1_0-10_nosym_sp_cmp.ps}
 %\end{center}
@@ -668,7 +664,7 @@ For this reason, the assumption that C diffusion and reorientation is achieved b
 \subsection{Migration described by classical potential calculations}
 \label{subsection:defects:mig_classical}
 
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{bc_00-1_albe_s.ps}
 %\includegraphics[width=13cm]{bc_00-1.ps}\\[5.6cm]
@@ -730,7 +726,7 @@ If the entire transition of the \hkl<0 0 -1> into the \hkl<0 0 1> configuration
 Assuming equal preexponential factors for both diffusion steps, the total probability of diffusion is given by $\exp\left((2.2\,\text{eV}+0.5\,\text{eV})/k_{\text{B}}T\right)$.
 Thus, the activation energy should be located within the range of \unit[2.2-2.7]{eV}.
 
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=13cm]{00-1_0-10.ps}\\[2.4cm]
 \begin{pspicture}(0,0)(0,0)
@@ -756,7 +752,7 @@ Thus, the activation energy should be located within the range of \unit[2.2-2.7]
 % red: ./visualize -w 640 -h 480 -d saves/c_in_si_mig_00-1_0-10_s20 -nll -0.56 -0.56 -0.8 -fur 0.3 0.2 0 -c -0.125 -1.7 0.7 -L -0.125 -0.25 -0.25 -r 0.6 -B 0.1
 \label{fig:defects:cp_00-1_0-10_mig}
 \end{figure}
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{00-1_ip0-10.ps}
 \end{center}
@@ -776,7 +772,7 @@ As mentioned above, the starting configuration of the first migration path, i.e.
 Further relaxation of the BC configuration results in the \ci{} \hkl<1 1 0> configuration.
 Even the last two pathways show configurations almost identical to the \ci{} \hkl<1 1 0> configuration, which constitute local minima within the pathways.
 Thus, migration pathways involving the \ci{} \hkl<1 1 0> DB configuration as a starting or final configuration are further investigated.
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{110_mig.ps}
 \end{center}
@@ -792,7 +788,7 @@ In contrast to quantum-mechanical calculations, in which the direct transition i
 Thus the just proposed migration path, which involves the \hkl<1 1 0> interstitial configuration, becomes even more probable than the initially porposed path, which involves the BC configuration that is, in fact, unstable.
 Due to these findings, the respective path is proposed to constitute the diffusion-describing path.
 The evolution of structure and configurational energy is displayed again in Fig. \ref{fig:defects:involve110}.
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{00-1_110_0-10_mig_albe.ps}
 \end{center}
@@ -814,15 +810,13 @@ Thus, atomic diffusion is wrongly described in the classical potential approach.
 The probability of already rare diffusion events is further decreased for this reason.
 However, agglomeration of C and diffusion of Si self-interstitials are an important part of the proposed SiC precipitation mechanism.
 Thus, a serious limitation that has to be taken into account for appropriately modeling the C/Si system using the otherwise quite promising EA potential is revealed.
-Possible workarounds are discussed in more detail in section \ref{subsection:md:limit}.
-
-\clearpage{}
+Possible workarounds are discussed in more detail in section \ref{section:md:limit}.
 
 \section{Combination of point defects}
 
 The study proceeds with a structural and energetic investigation of pairs of the ground-state and, thus, most probable defect configurations that are believed to be fundamental in the Si to SiC conversion.
 Investigations are restricted to quantum-mechanical calculations.
-\begin{figure}[t]
+\begin{figure}[tp]
 \begin{center}
 \subfigure[]{\label{fig:defects:combos_ci}\includegraphics[width=0.3\textwidth]{combos_ci.eps}}
 \hspace{0.5cm}
@@ -839,7 +833,7 @@ Next to formation and binding energies, migration barriers are investigated, whi
 \label{subsection:defects:c-si_comb}
 
 \ci{} pairs of the \hkl<1 0 0>-type are investigated in the first part.
-\begin{table}[ht]
+\begin{table}[tp]
 \begin{center}
 \begin{tabular}{l c c c c c c}
 \hline
@@ -873,7 +867,7 @@ Energetically favorable and unfavorable configurations can be explained by stres
 Antiparallel orientations of the second defect, i.e. \hkl[0 0 1] for positions located below the \hkl(0 0 1) plane with respect to the initial one (positions 1, 2 and 4) form the energetically most unfavorable configurations.
 In contrast, the parallel and particularly the twisted orientations constitute energetically favorable configurations, in which a vast reduction of strain is enabled by combination of these defects.
 
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \subfigure[\underline{$E_{\text{b}}=-2.25\,\text{eV}$}]{\label{fig:defects:225}\includegraphics[width=0.3\textwidth]{00-1dc/2-25.eps}}
 \hspace{0.5cm}
@@ -902,7 +896,7 @@ However, the second most favorable configuration ($E_{\text{f}}=-2.25\,\text{eV}
 Thus, particularly at high temepratures that cause an increase of the entropic contribution, this structure constitutes a serious opponent to the ground state.
 In fact, following results on migration simulations will reinforce the assumption of a low probability for C clustering by thermally activated processes.
 
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \subfigure[\underline{$E_{\text{b}}=-2.16\,\text{eV}$}]{\label{fig:defects:216}\includegraphics[width=0.25\textwidth]{00-1dc/2-16.eps}}
 \hspace{0.2cm}
@@ -947,7 +941,7 @@ Both configurations are unfavorable compared to far-off, isolated DBs.
 Nonparallel orientations, i.e. the \hkl[0 1 0], \hkl[0 -1 0] and its equivalents, result in binding energies of \unit[-0.12]{eV} and \unit[-0.27]{eV}, thus, constituting energetically favorable configurations.
 The reduction of strain energy is higher in the second case, where the C atom of the second DB is placed in the direction pointing away from the initial C atom.
 
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \subfigure[\underline{$E_{\text{b}}=-1.53\,\text{eV}$}]{\label{fig:defects:153}\includegraphics[width=0.25\textwidth]{00-1dc/1-53.eps}}
 \hspace{0.7cm}
@@ -977,7 +971,7 @@ In both configurations, the far-off atom of the second DB resides in threefold c
 
 The interaction of \ci{} \hkl<1 0 0> DBs is investigated along the \hkl[1 1 0] bond chain assuming a possible reorientation of the DB atom at each position to minimize its configurational energy.
 Therefore, the binding energies of the energetically most favorable configurations with the second DB located along the \hkl[1 1 0] direction and resulting C-C distances of the relaxed structures are summarized in Table~\ref{tab:defects:comb_db110}.
-\begin{table}[ht]
+\begin{table}[tp]
 \begin{center}
 \begin{tabular}{l c c c c c c}
 \hline
@@ -995,7 +989,7 @@ Type & \hkl[-1 0 0] & \hkl[1 0 0] & \hkl[1 0 0] & \hkl[1 0 0] & \hkl[1 0 0] & \h
 \label{tab:defects:comb_db110}
 \end{table}
 %
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{db_along_110_cc_n.ps}
 \end{center}
@@ -1018,7 +1012,7 @@ The high activation energy is attributed to the stability of such a low energy c
 Low barriers are only identified for transitions starting from energetically less favorable configurations, e.g. the configuration of a \hkl[-1 0 0] DB located at position 2 (\unit[-0.36]{eV}).
 Starting from this configuration, an activation energy of only \unit[1.2]{eV} is necessary for the transition into the ground state configuration.
 The corresponding migration energies and atomic configurations are displayed in Fig.~\ref{fig:036-239}.
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{036-239.ps}
 \end{center}
@@ -1037,7 +1031,7 @@ In both cases the configuration yielding a binding energy of \unit[-2.25]{eV} is
 First of all, it constitutes the second most energetically favorable structure.
 Secondly, a migration path with a barrier as low as \unit[0.47]{eV} exists starting from a configuration of largely separated defects exhibiting a low binding energy (\unit[-1.88]{eV}).
 The migration barrier and corresponding structures are shown in Fig.~\ref{fig:188-225}.
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{188-225.ps}
 \end{center}
@@ -1051,7 +1045,7 @@ As a result, C defect agglomeration indeed is expected, but only a low probabili
 \subsection[Combinations of the \ci{} \hkl<1 0 0> and \cs{} type]{\boldmath Combinations of the \ci{} \hkl<1 0 0> and \cs{} type}
 \label{subsection:defects:c-csub}
 
-\begin{table}[ht]
+\begin{table}[tp]
 \begin{center}
 \begin{tabular}{c c c c c c}
 \hline
@@ -1067,7 +1061,7 @@ As a result, C defect agglomeration indeed is expected, but only a low probabili
 \caption{Binding energies of combinations of the \ci{} \hkl[0 0 -1] defect with a \cs{} atom located at positions 1 to 5 according to Fig.~\ref{fig:defects:combos_ci}. R corresponds to the position located at $\frac{a_{\text{Si}}}{2}\hkl[3 2 3]$ relative to the initial defect position, which is the maximum realizable distance due to periodic boundary conditions.}
 \label{tab:defects:c-s}
 \end{table}
-%\begin{figure}[ht]
+%\begin{figure}[tp]
 %\begin{center}
 %\begin{minipage}[t]{5cm}
 %a) \underline{Pos: 1, $E_{\text{b}}=0.26\text{ eV}$}
@@ -1091,7 +1085,7 @@ As a result, C defect agglomeration indeed is expected, but only a low probabili
 %\caption{Relaxed structures of defect complexes obtained by creating a carbon substitutional at position 1 (a)), 3 (b)) and 5 (c)).}
 %\label{fig:defects:comb_db_04}
 %\end{figure}
-%\begin{figure}[ht]
+%\begin{figure}[tp]
 %\begin{center}
 %\begin{minipage}[t]{7cm}
 %a) \underline{Pos: 2, $E_{\text{b}}=-0.51\text{ eV}$}
@@ -1117,7 +1111,7 @@ Fig.~\ref{fig:093-095} and \ref{fig:026-128} show structures A, B and a, b toget
 
 % A B
 %./visualize_contcar -w 640 -h 480 -d results/c_00-1_c3_csub_B -nll -0.20 -0.4 -0.1 -fur 0.9 0.6 0.9 -c 0.5 -1.5 0.375 -L 0.5 0 0.3 -r 0.6 -A -1 2.465
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{093-095.ps}
 \end{center}
@@ -1139,7 +1133,7 @@ Obviously, either the CRT algorithm fails to seize the actual saddle point struc
 % not satisfactory!
 
 % a b
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{026-128.ps}
 \end{center}
@@ -1179,7 +1173,7 @@ This structure is followed by C$_{\text{s}}$ located at position 2, the lattice
 As mentioned earlier, these two lower Si atoms indeed experience tensile strain along the \hkl[1 1 0] bond chain, however, additional compressive strain along \hkl[0 0 1] exists.
 The latter is partially compensated by the C$_{\text{s}}$ atom.
 Yet less of compensation is realized if C$_{\text{s}}$ is located at position 4 due to a larger separation although both bottom Si atoms of the DB structure are indirectly affected, i.e. each of them is connected by another Si atom to the C atom enabling the reduction of strain along \hkl[0 0 1].
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \subfigure[\underline{$E_{\text{b}}=-0.51\,\text{eV}$}]{\label{fig:defects:051}\includegraphics[width=0.25\textwidth]{00-1dc/0-51.eps}}
 \hspace{0.2cm}
@@ -1232,8 +1226,9 @@ For the same reasons as in the last subsection, structures other than the ground
 In the last section, configurations of a C$_{\text{i}}$ DB with C$_{\text{s}}$ occupying a vacant site have been investigated.
 Additionally, configurations might arise in IBS, in which the impinging C atom creates a vacant site near a C$_{\text{i}}$ DB, but does not occupy it.
 These structures are investigated in the following.
+
 Resulting binding energies of a C$_{\text{i}}$ DB and a nearby vacancy are listed in the second row of Table~\ref{tab:defects:c-v}.
-\begin{table}[ht]
+\begin{table}[tp]
 \begin{center}
 \begin{tabular}{c c c c c c}
 \hline
@@ -1248,7 +1243,7 @@ Resulting binding energies of a C$_{\text{i}}$ DB and a nearby vacancy are liste
 \caption{Binding energies of combinations of the \ci{} \hkl[0 0 -1] defect with a vacancy located at positions 1 to 5 according to Fig.~\ref{fig:defects:combos_ci}. R corresponds to the position located at $\frac{a_{\text{Si}}}{2}\hkl[3 2 3]$ relative to the initial defect position, which is the maximum realizable distance due to periodic boundary conditions.}
 \label{tab:defects:c-v}
 \end{table}
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \subfigure[\underline{$E_{\text{b}}=-0.59\,\text{eV}$}]{\label{fig:defects:059}\includegraphics[width=0.25\textwidth]{00-1dc/0-59.eps}}
 \hspace{0.7cm}
@@ -1289,14 +1284,14 @@ Strain reduced by this huge displacement is partially absorbed by tensile strain
 A binding energy of \unit[-0.50]{eV} is observed.
 
 The migration pathways of configuration \ref{fig:defects:314} and \ref{fig:defects:059} into the ground-state configuration, i.e. the \cs{} configuration, are shown in Fig.~\ref{fig:314-539} and \ref{fig:059-539} respectively.
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{314-539.ps}
 \end{center}
 \caption{Migration barrier and structures of the transition of the initial C$_{\text{i}}$ \hkl[0 0 -1] DB and a V created at position 3 (left) into a C$_{\text{s}}$ configuration (right). An activation energy of \unit[0.1]{eV} is observed.}
 \label{fig:314-539}
 \end{figure}
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{059-539.ps}
 \end{center}
@@ -1331,8 +1326,6 @@ Furthermore, small activation energies, even for transitions into the ground sta
 If the vacancy is created at position 1 the system will end up in a configuration of C$_{\text{s}}$ anyways.
 Based on these results, a high probability for the formation of C$_{\text{s}}$ must be concluded.
 
-%\clearpage{}
-
 \subsection{Combinations of \si{} and \cs}
 \label{subsection:si-cs}
 
@@ -1344,7 +1337,7 @@ Thus, combinations of \cs{} and an additional \si{} are examined in the followin
 The ground-state of a single \si{} was found to be the \si{} \hkl<1 1 0> DB configuration.
 For the follwoing study the same type of self-interstitial is assumed to provide the energetically most favorable configuration in combination with \cs.
 
-\begin{table}[ht]
+\begin{table}[tp]
 \begin{center}
 \begin{tabular}{l c c c c c c}
 \hline
@@ -1364,7 +1357,7 @@ For the follwoing study the same type of self-interstitial is assumed to provide
 \caption{Equivalent configurations labeled \RM{1}-\RM{10} of \hkl<1 1 0>-type Si$_{\text{i}}$ DBs created at position I and C$_{\text{s}}$ created at positions 1 to 5 according to Fig.~\ref{fig:defects:combos_si}. The respective orientation of the Si$_{\text{i}}$ DB is given in the first row.}
 \label{tab:defects:comb_csub_si110}
 \end{table}
-\begin{table}[ht]
+\begin{table}[tp]
 \begin{center}
 \begin{tabular}{l c c c c c c c c c c}
 \hline
@@ -1397,7 +1390,7 @@ Thus, the compressive stress along \hkl[1 1 0] of the \si{} \hkl[1 1 0] DB is no
 
 However, even configuration \RM{1} is energetically less favorable than the \hkl<1 0 0> C$_{\text{i}}$ DB, which, thus, remains the ground state of a C atom introduced into otherwise perfect c-Si.
 The transition involving the latter two configurations is shown in Fig.~\ref{fig:162-097}.
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{162-097.ps}
 \end{center}
@@ -1409,7 +1402,7 @@ Accordingly, the C$_{\text{i}}$ \hkl<1 0 0> DB configuration is assumed to occur
 However, only \unit[0.77]{eV} are needed for the reverse process, i.e. the formation of C$_{\text{s}}$ and a Si$_{\text{i}}$ DB out of the ground state.
 Due to the low activation energy this process must be considered to be activated without much effort either thermally or by introduced energy of the implantation process.
 
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \includegraphics[width=0.7\textwidth]{c_sub_si110.ps}
 \end{center}
@@ -1437,14 +1430,14 @@ Similar to what was previously mentioned, configurations of C$_{\text{s}}$ and a
 At higher temperatures, the contribution of entropy to structural formation increases, which might result in a spatial separation even for defects located within the capture radius.
 Indeed, an {em ab initio} MD run at \unit[900]{$^{\circ}$C} starting from configuration \RM{1}, which -- based on the above findings -- is assumed to recombine into the ground state configuration, results in a separation of the C$_{\text{s}}$ and Si$_{\text{i}}$ DB by more than 4 neighbor distances realized in a repeated migration mechanism of annihilating and arising Si$_{\text{i}}$  DBs.
 The atomic configurations for two different points in time are shown in Fig.~\ref{fig:defects:md}.
-\begin{figure}[ht]
+\begin{figure}[tp]
 \begin{center}
 \begin{minipage}{0.40\textwidth}
-\includegraphics[width=\columnwidth]{md01.eps}
+\includegraphics[width=\columnwidth]{md_vasp_01.eps}
 \end{minipage}
 \hspace{1cm}
 \begin{minipage}{0.40\textwidth}
-\includegraphics[width=\columnwidth]{md02.eps}\\
+\includegraphics[width=\columnwidth]{md_vasp_02.eps}
 \end{minipage}\\
 \begin{minipage}{0.40\textwidth}
 \begin{center}
@@ -1468,7 +1461,7 @@ These results support the above assumptions of an increased entropic contributio
 
 %\section{Migration in systems of combined defects}
 
-%\begin{figure}[ht]
+%\begin{figure}[tp]
 %\begin{center}
 %\includegraphics[width=13cm]{vasp_mig/comb_mig_3-2_vac_fullct.ps}\\[2.0cm]
 %\begin{picture}(0,0)(170,0)
@@ -1493,7 +1486,7 @@ These results support the above assumptions of an increased entropic contributio
 %\caption{Transition of the configuration of the C-Si dumbbell interstitial in combination with a vacancy created at position 2 into the configuration of substitutional carbon.}
 %\label{fig:defects:comb_mig_01}
 %\end{figure}
-%\begin{figure}[ht]
+%\begin{figure}[tp]
 %\begin{center}
 %\includegraphics[width=13cm]{vasp_mig/comb_mig_4-2_vac_fullct.ps}\\[1.0cm]
 %\begin{picture}(0,0)(150,0)
@@ -1519,8 +1512,6 @@ These results support the above assumptions of an increased entropic contributio
 %\label{fig:defects:comb_mig_02}
 %\end{figure}
 
-\clearpage{}
-
 \section{Applicability: Competition of \ci{} and \cs-\si{}}
 \label{section:ea_app}
 
@@ -1535,7 +1526,7 @@ Since quantum-mechanical calculations reveal the Si$_{\text{i}}$ \hkl<1 1 0> DB
 Empirical potentials, however, predict Si$_{\text{i}}$ T to be the energetically most favorable configuration.
 Thus, investigations of the relative energies of formation of defect pairs need to include combinations of C$_{\text{s}}$ with Si$_{\text{i}}$ T.
 Results of {\em ab initio} and classical potential calculations are summarized in Table~\ref{tab:defect_combos}.
-\begin{table}[t]
+\begin{table}[tp]
 \begin{center}
 \begin{tabular}{l c c c}
 \hline
@@ -1650,8 +1641,6 @@ In contrast, there is no obvious reason for the topotactic orientation of an agg
 
 \ifnum1=0
 
-
-
 In addition, there are experimental findings, which might be exploited to reinforce the non-validity of the proposed precipitation model.
 High resolution TEM shows equal orientation of \hkl(h k l) planes of the c-Si host matrix and the 3C-SiC precipitate.