X-Git-Url: https://hackdaworld.org/gitweb/?p=lectures%2Flatex.git;a=blobdiff_plain;f=posic%2Fthesis%2Fsic.tex;h=b6179d21325bbac0ab3f2505aeb7dde980dccfdd;hp=8625011fa1bdb36120a346ba371e3bbcb402b0cd;hb=308fce67d5c701822d5cb2d960a056644498cd03;hpb=4c26ce3943e912490d74ffa043fe0f297a02c04b diff --git a/posic/thesis/sic.tex b/posic/thesis/sic.tex index 8625011..b6179d2 100644 --- a/posic/thesis/sic.tex +++ b/posic/thesis/sic.tex @@ -217,7 +217,7 @@ The cleaned substrate surface shows a C terminated $(2\times 2)$ pattern at \uni 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. @@ -291,7 +291,7 @@ As expected, single-crystalline layers were achieved for an increased temperatur 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.