-The cleaned substrate surface shows a $(1\times 1)$ pattern at \unit[1000]{$^{\circ}$C}, which turns into a $(3\times 2)$ pattern when Si$_2$H$_6$ is introduced and it is maintained after the supply is stopped.
-A more detailed investigation showed the formation of a preceeding $(2\times 1)$ pattern within the exposure to the Si containing gas \cite{yoshinobu90}.
-The $(3\times 2)$ superstructure contains approximately 1.7 monolayers of Si atoms.
-The insertion of C$_2$H$_6$ leads to a reconstruction of the surface into the initial $(1\times 1)$ pattern and the formation of crystalline 3C-SiC with a smooth and mirror-like surface after an appropriate number of cycles.
-The growth rate ... higher, due to physically adsorbed Si, which depends on Si supply ...
-Not really ALE ... 1.7 monolayers per cycle ... now real ALE \cite{fuyuki93,hara93}
-6H on 6H ... \cite{tanaka94}
-Problem of gas source ... strong adsorption and incorporation of atomic decomposited hydrogen of the gas phase reactants at low temperatures.
-Growth rate lower than desorption rate of hydrogen ...
-Solid source MBE may be the key to avoid such problems ...
-Realized on and off-axis 3C on 4H and ... \cite{fissel95,fissel95_apl} ...
-Nonstoichiometric reconstruction plays a relevenat role ... handled by Si/C flux ratio ... \cite{fissel96,righi03} ...
-change in adlayer thickness and, consequently, in the surface super structure leading to growth of another polytype \cite{fissel95} ...
-Possibility to grow heterostructures (band gap engineering) by careful control of the Si/C ratio and Si excess.
-
-To summarize ... remaining obstacles are ... APB in 3C ... and micropipes in hexagonal SiC?
-
-\section{Ion beam synthesis of cubic silicon carbide}
+The cleaned substrate surface shows a C terminated $(2\times 2)$ pattern at \unit[1000]{$^{\circ}$C}, which turns into a $(3\times 2)$ pattern when Si$_2$H$_6$ is introduced and it is maintained after the supply is stopped.
+A more detailed investigation showed the formation of a preceeding $(2\times 1)$ and $(5\times 2)$ pattern within the exposure to the Si containing gas \cite{yoshinobu90,fuyuki93}.
+The $(3\times 2)$ superstructure contains approximately 1.7 monolayers of Si atoms, crystallizing into 3C-SiC with a smooth and mirror-like surface after C$_2$H$_6$ is inserted accompanied by a reconstruction of the surface into the initial C terminated $(2\times 2)$ pattern.
+A minimal growth rate of 2.3 monolayers per cycle exceeding the value of 1.7 is due to physically adsorbed Si atoms not contributing to the superstructure.
+To realize single monolayer growth precise control of the gas supply to form the $(2\times 1)$ structure is required.
+However, accurate layer-by-layer growth is achieved under certain conditions, which facilitate the spontaneous desorption of an additional layer of one atom species by supply of the other species \cite{hara93}.
+Homoepitaxial growth of the 6H polytype has been realized on off-oriented substrates utilizing simultaneous supply of the source gases \cite{tanaka94}.
+Depending on the gas flow ratio either 3C island formation or step flow growth of the 6H polytype occurs, which is explained by a model including aspects of enhanced surface mobilities of adatoms on a $(3\times 3)$ reconstructed surface.
+Due to the strong adsorption of atomic hydrogen \cite{allendorf91} decomposited of the gas phase reactants at low temperatures, however, there seems to be no benefit of GSMBE compared to \ac{CVD}.
+Next to lattice imperfections, incorporated hydrogen effects the surface mobility of the adsorbed species \cite{eaglesham93} setting a minimum limit for the growth temperature, which would preferably be further decreased in order to obtain sharp doping profiles.
+Thus, growth rates must be adjusted to be lower than the desorption rate of hydrogen, which leads to very low deposition rates at low temperatures.
+SSMBE, by supplying the atomic species to be deposited by evaporation of a solid, presumably constitutes the preffered method in order to avoid the problems mentioned above.
+Although, in the first experiments, temperatures still above \unit[1100]{$^{\circ}$C} were necessary to epitaxially grow 3C-SiC films on 6H-SiC substrates \cite{kaneda87}, subsequent attempts succeeded in growing mixtures of twinned 3C-SiC and 6H-SiC films on off-axis \hkl(0001) 6H-SiC wafers at temperatures between \unit[800]{$^{\circ}$C} and \unit[1000]{$^{\circ}$C} \cite{fissel95,fissel95_apl}.
+In the latter approach, as in GSMBE, excess Si atoms, which are controlled by the Si/C flux ratio, result in the formation of a Si adlayer and the formation of a non-stoichiometric, reconstructed surface superstructure, which influences the mobility of adatoms and, thus, has a decisive influence on the growth mode, polytype and crystallinity \cite{fissel95,fissel96,righi03}.
+Therefore, carefully controlling the Si/C ratio could be exploited to obtain definite heterostructures of different SiC polytypes providing the possibility for band gap engineering in SiC materials.
+
+To summarize, much progress has been achieved in SiC thin film growth during the last few years.
+However, the frequent occurence of defects such as dislocations, twins and double positioning boundaries limit the structural and electrical quality of large SiC films.
+Solving this issue remains a challenging problem necessary to drive SiC for potential applications in high-performance electronic device production \cite{wesch96}.
+
+\subsection{Ion beam synthesis of cubic silicon carbide}
+
+Although tremendous progress has been achieved in the above-mentioned growth methods during the last decades, available wafer dimensions and crystal qualities are not yet statisfactory.
+Thus, alternative approaches to fabricate SiC have been explored.
+The \ac{IBS} technique, i.e. high-dose ion implantation followed by a high-temperature annealing step, turned out to constitute a promising method to directly form compound layers of high purity and accurately controllable depth and stoichiometry.
+A short chronological summary of the \ac{IBS} of SiC and its origins is presented in the following.
+
+High-dose carbon implantation into \ac{c-Si} with subsequent or in situ annealing was found to result in SiC microcrystallites in Si \cite{borders71}.
+\ac{RBS} and \ac{IR} spectroscopy investigations indicate a \unit[10]{at.\%} C concentration peak and the occurence of disordered C-Si bonds after implantation at \ac{RT} followed by crystallization into SiC precipitates upon annealing demonstrated by a shift in the \ac{IR} absorption band and the disappearance of the C profile peak in \ac{RBS}.
+Implantations at different temperatures revealed a strong influence of the implantation temperature on the compound structure \cite{edelman76}.
+Temperatures below \unit[500]{$^{\circ}$C} result in amorphous layers, which is transformed into polycrystalline 3C-SiC after \unit[850]{$^{\circ}$C} annealing.
+Otherwise single crystalline 3C-SiC is observed for temperatures above \unit[600]{$^{\circ}$C}.
+Annealing temperatures necessary for the onset of the amorphous to crystalline transition have been confirmed by further studies \cite{kimura81,kimura82}.
+Overstoichiometric doses result in the formation of clusters of C, which do not contribute to SiC formation during annealing up to \unit[1200]{$^{\circ}$C} \cite{kimura82}.
+The amount of formed SiC, however, increases with increasing implantation temperature.
+The authors, thus, concluded that implantations at elevated temperatures lead to a reduction in the annealing temperatures required for the synthesis of homogeneous layers of SiC.
+In a comparative study of O, N and C implantation into Si, the absence of the formation of a stoichiometric SiC compound layer involving the transition of a Gaussian into a box-like C profile with respect to the implantation depth for the superstoichiometric C implantation and an annealing temeprature of \unit[1200]{$^{\circ}$C} in contrast to the O and N implantations, which successfully form homogeneous layers, has been observed \cite{reeson86}.
+This was attrubuted to the difference in the enthalpy of formation of the respective compound and the different mobility of the respective impurity in bulk Si.
+Thus, higher annealing temperatures and longer annealing times were considered necessary for the formation of homogeneous SiC layers.
+Indeed, for the first time, buried homogeneous and stoichiometric epitaxial 3C-SiC layers embedded in single crystalline Si were obtained by the same group consequently applying annealing temperatures of \unit[1405]{$^{\circ}$C} for \unit[90]{min} and implantation temperatures of approximately \unit[550]{$^{\circ}$C} \cite{reeson87}.
+The necessity of the applied extreme temperature and time scale is attributed to the stability of substitutional C within the Si matrix being responsible for high activation energies necessary to dissolve such precipitates and, thus, allow for redistribution of the implanted C atoms.
+In order to avoid extreme annealing temperatures close to the melting temperature of Si, triple-energy implantations in the range from \unit[180-190]{keV} with stoichiometric doses at a constant target temperature of \unit[860]{$^{\circ}$C} achieved by external substrate heating were performed \cite{martin90}.
+It was shown that a thick buried layer of SiC is directly formed during implantation, which consists of small, only slightly misorientated but severely twinned 3C-SiC crystallites.
+The authors assumed that due to the auxiliary heating rather than ion beam heating as employed in all the preceding studies, the complexity of the remaining defects in the synthsized structure is fairly reduced.
+Since no amorphous or polycrystalline regions have been identified, twinning is considered to constitute the main limiting factor in the \ac{IBS} of SiC.
+... maybe nejim?!?
+... lindner limit in dose -> 1250
+... two temp implantation ... sharp interface
+By understanding some basic processes (32-36), \ac{IBS} nowadays has become a promising method to form thin SiC layers of high quality exclusively of the 3C polytype embedded in and epitactically aligned to the Si host featuring a sharp interface \cite{lindner99,lindner01,lindner02}.