X-Git-Url: https://hackdaworld.org/gitweb/?a=blobdiff_plain;f=posic%2Fthesis%2Fsic.tex;h=cb46a7b4b5b238ba07400122f5bc09c0365bb044;hb=0e3045d3f913a46eb0f58c6674b26c2642cccfc0;hp=0379687e3eab31da63bc58ad8aa752a43daaf38b;hpb=cf625066e6ada2a8d680e2a77bb2f5c6eb5122ab;p=lectures%2Flatex.git diff --git a/posic/thesis/sic.tex b/posic/thesis/sic.tex index 0379687..cb46a7b 100644 --- a/posic/thesis/sic.tex +++ b/posic/thesis/sic.tex @@ -51,9 +51,10 @@ Thermal conductivity [W/cmK] & 5.0 & 4.9 & 4.9 & 1.5 & 1.3 & 22 \\ \hline \end{tabular} \end{center} -\caption[Properties of SiC polytypes and other semiconductor materials.]{Properties of SiC polytypes and other semiconductor materials. Doping concentrations are $10^{16}\text{ cm}^{-3}$ (A) and $10^{17}\text{ cm}^{-3}$ (B) respectively. References: \cite{wesch96,casady96,park98}. {\color{red}Todo: add more refs + check all values!}} +\caption[Properties of SiC polytypes and other semiconductor materials.]{Properties of SiC polytypes and other semiconductor materials. Doping concentrations are $10^{16}\text{ cm}^{-3}$ (A) and $10^{17}\text{ cm}^{-3}$ (B) respectively. References: \cite{wesch96,casady96,park98}.} \label{table:sic:properties} \end{table} +% todo add more refs + check all values! Different polytypes of SiC exhibit different properties. Some of the key properties are listed in Table~\ref{table:sic:properties} and compared to other technologically relevant semiconductor materials. Despite the lower charge carrier mobilities for low electric fields SiC outperforms Si concerning all other properties. @@ -342,7 +343,7 @@ However, there is great interest to incorporate C onto substitutional lattice si Thus, substitutional C enables strain engineering of Si and Si/Si$_{1-x}$Ge$_x$ heterostructures \cite{yagi02,chang05,kissinger94,osten97}, which is used to increase charge carrier mobilities in Si as well as to adjust its band structure \cite{soref91,kasper91}. % increase of C at substitutional sites Epitaxial layers with \unit[1.4]{at.\%} of substitutional C have been successfully synthesized in preamorphized Si$_{0.86}$Ge$_{0.14}$ layers, which were grown by CVD on Si substrates, using multiple-energy C implantation followed by solid-physe epitaxial regrowth at \unit[700]{$^{\circ}$C} \cite{strane93}. -The tensile strain induced by the C atoms is found to compensates the compressive strain present due to the Ge atoms. +The tensile strain induced by the C atoms is found to compensate the compressive strain present due to the Ge atoms. Studies on the thermal stability of Si$_{1-y}$C$_y$/Si heterostructures formed in the same way and equal C concentrations showed a loss of substitutional C accompanied by strain relaxation for temperatures ranging from \unit[810-925]{$^{\circ}$C} and the formation of spherical 3C-SiC precipitates with diameters of \unit[2-4]{nm}, which are incoherent but aligned to the Si host \cite{strane94}. During the initial stages of precipitation C-rich clusters are assumed, which maintain coherency with the Si matrix and the associated biaxial strain. Using this technique a metastable solubility limit was achieved, which corresponds to a C concentration exceeding the solid solubility limit at the Si melting point by nearly three orders of magnitude and, furthermore, a reduction of the defect denisty near the metastable solubility limit is assumed if the regrowth temperature is increased by rapid thermal annealing \cite{strane96}. @@ -359,7 +360,7 @@ Indeed, closely investigating the large amount of literature pulled up in the la High resolution transmission electron microscopy (HREM) investigations of C-implanted Si at room temperature followed by rapid thermal annealing (RTA) show the formation of C-Si dumbbell agglomerates, which are stable up to annealing temperatures of about \unit[700-800]{$^{\circ}$C}, and a transformation into 3C-SiC precipitates at higher temperatures \cite{werner96,werner97}. The precipitates with diamateres between \unit[2]{nm} and \unit[5]{nm} are incorporated in the Si matrix without any remarkable strain fields, which is explained by the nearly equal atomic density of C-Si agglomerates and the SiC unit cell. Implantations at \unit[500]{$^{\circ}$C} likewise suggest an initial formation of C-Si dumbbells on regular Si lattice sites, which agglomerate into large clusters \cite{lindner99_2}. -The agglomerates of such dimers, which do not generate lattice strain but lead to a local increase of the lattice potential \cite{werner96}, are indicated by dark contrasts and otherwise undisturbed Si lattice fringes in HREM, as can be seen in Fig.~\ref{fig:sic:hrem:c-si}. +The agglomerates of such dimers, which do not generate lattice strain but lead to a local increase of the lattice potential \cite{werner96,werner97}, are indicated by dark contrasts and otherwise undisturbed Si lattice fringes in HREM, as can be seen in Fig.~\ref{fig:sic:hrem:c-si}. \begin{figure}[t] \begin{center} \subfigure[]{\label{fig:sic:hrem:c-si}\includegraphics[width=0.25\columnwidth]{tem_c-si-db.eps}} @@ -418,7 +419,7 @@ On the other hand, processes relying upon prevention of precipitation in order t % eichhorn02: high imp temp more efficient than postimp treatment % eichhorn99: same as 02 + c-si agglomerates at low concentrations % strane94/guedj98: my model - c redist by si int (spe) and surface diff (mbe) +% serre95: low/high t implants -> mobile c_i / non-mobile sic precipitates -% todo -% own polytype stacking sequence image +% todo - own polytype stacking sequence image