A more detailed investigation showed the formation of a preceding $(2\times 1)$ 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.
+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.
However, these layers show an extremely poor interface to the Si top layer governed by a high density of SiC precipitates, which are not affected in the C redistribution during annealing and, thus, responsible for the rough interface.
Hence, to obtain sharp interfaces and single-crystalline SiC layers temperatures between \unit[400]{$^{\circ}$C} and \unit[600]{$^{\circ}$C} have to be used.
Indeed, reasonable results were obtained at \unit[500]{$^{\circ}$C}~\cite{lindner98} and even better interfaces were observed for \unit[450]{$^{\circ}$C}~\cite{lindner99_2}.
-To further improve the interface quality and crystallinity a two-temperature implantation technique was developed~\cite{lindner99}.
+To further improve the interface quality and crystallinity, a two-temperature implantation technique was developed~\cite{lindner99}.
To form a narrow, box-like density profile of oriented SiC nanocrystals, \unit[93]{\%} of the total dose of \unit[$8.5\cdot 10^{17}$]{cm$^{-2}$} is implanted at \unit[500]{$^{\circ}$C}.
The remaining dose is implanted at \unit[250]{$^{\circ}$C}, which leads to the formation of amorphous zones above and below the SiC precipitate layer and the destruction of SiC nanocrystals within these zones.
After annealing for \unit[10]{h} at \unit[1250]{$^{\circ}$C} a homogeneous, stoichiometric SiC layer with sharp interfaces is formed.
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