% lattice location of implanted carbon
Radiation damage introduced during implantation and a high concentration of the implanted species, which results in the reduction of the topological constraint of the host lattice imposed on the implanted species, can affect the manner of impurity incorporation.
-The probability of finding C, which will be most stable at sites for which the number of neighbors equals the natural valence, i.e. substitutionally on a regular Si site of a perfect lattice, is, thus, reduced at substitutional lattice sites and likewise increased to be found as an interstitial.
-Depending on the way C is incorporated and whether precipitation occurs or not the volume is either reduced in the case of substitutionally incorporated C or expanded in the case of C interstitial formation \cite{goesele85}.
-
-There are, however, ...
-In implanted Si the location of C is to a great deal incorporated as an interstitial atom due to a reduced topological contraint.
-Other methods exist to realize only substitutional C.
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-% -> my own links: strane etc ...
-% -> skorupa 3.5: heterostructures
-
-\section{Assumed cubic silicon carbide conversion mechanisms}
+The probability of finding C, which will be most stable at sites for which the number of neighbors equals the natural valence, i.e. substitutionally on a regular Si site of a perfect lattice, is, thus, reduced at substitutional lattice sites and likewise increased at interstitial sites.
+Indeed, x-ray rocking curves reveal a positive lattice strain, which is decreased but still remains with increasing annealing temeprature, indicating the location of the majority of implanted C atoms at interstitial sites \cite{isomae93}.
+Due to the absence of dislocations in the implanted region interstitial C is assumed to prevent clustering of implantation-induced Si self-interstitials by agglomeration of C-Si interstitials or the formation of SiC precipitates accompanied by a relaxation of the lattice strain.
+
+% link to strain engineering
+However, there is great interest to incorporate C onto substitutional lattice sites, which results in a contraction of the Si lattice due to the smaller covalent radius of C compared to Si \cite{baker68}, causing tensile strain, which is applied to the Si lattice.
+Thus, substitutional C enables strain engineering of Si and Si/Si$_{1-x}$Ge$_x$ heterostructures \cite{yagi02,chang05,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.
+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 a rapid thermal annealing process \cite{strane96}.
+By MBE ... \cite{powell93,osten99}
+
+\section{Assumed silicon carbide conversion mechanisms}
\label{section:assumed_prec}
Although much progress has been made in 3C-SiC thin film growth in the above-mentioned growth methods during the last decades, there is still potential
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