X-Git-Url: https://hackdaworld.org/gitweb/?a=blobdiff_plain;f=posic%2Fthesis%2Fsic.tex;h=1e6d91ca08762909808225d429caac77d673b6a8;hb=b3a906c2a0daba387d3a43fce271357e8c466552;hp=3514066d8925dff2f3eaae09c762e91fac7ec4f1;hpb=2b030e78f7f74881964d0883c4c2c25bf62b33f7;p=lectures%2Flatex.git

diff --git a/posic/thesis/sic.tex b/posic/thesis/sic.tex
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@@ -153,14 +153,40 @@ Further efforts have to be expended to find relations between the growth paramet
 \subsection{SiC epitaxial thin film growth}
 
 Crystalline SiC layers have been grown by a large number of techniques on the surfaces of different substrates.
-Most of the crystal growth processes are based on chemical vapor deposition (CVD), solid-source molecular beam epitaxy (MBE) and gas-source MBE on Si as well as SiC substrates, which will be exclusively reviewed in the following.
-
-
+Most of the crystal growth processes are based on chemical vapor deposition (CVD), solid-source molecular beam epitaxy (MBE) and gas-source MBE on Si as well as SiC substrates.
+In CVD as well as gas-source MBE, C and Si atoms are supplied by C containing gases like CH$_4$, C$_3$H$_8$, C$_2$H$_2$ or C$_2$H$_4$ and Si containing gases like SiH$_4$, Si$_2$H$_6$, SiH$_2$Cl$_2$, SiHCl$_3$ or SiCl$_4$ respectively.
+In the case of solid-source MBE atoms are provided by electron beam evaporation of graphite and solid Si or thermal evaporation of fullerenes.
+The following review will exclusively focus on CVD and MBE techniques.
+
+The availability and reproducibility of Si substrates of controlled purity made it the first choice for SiC epitaxy.
+The heteroepitaxial growth of SiC on Si substrates has been stimulated for a long time due to the lack of suitable large substrates that could be adopted for homoepitaxial growth.
+Furthermore, heteroepitaxy on Si substrates enables the fabrication of the advantageous 3C polytype, which constitutes a metastable phase and, thus, can be grown as a bulk crystal only with small sizes of a few mm.
+The main difficulties in SiC heteroepitaxy on Si is due to the lattice mismatch of Si and SiC and the difference in the thermal expansion coefficient of \unit[8]{\%}.
+Thus, in most of the applied CVD and MBE processes, the SiC layer formation process is split into two steps, the surface carbonization and the growth step, as proposed by Nishino~et~al. \cite{nishino83}.
+Cleaning of the substrate surface with HCl is required prior to carbonization.
+During carbonization the Si surface is chemically converted into a SiC film with a thickness of a few nm by exposing it to a flux of C atoms and concurrent heating up to temperatures about \unit[1400]{$^{\circ}$C}.
+In a next step, the epitaxial deposition of SiC is realized by an additional supply of Si atoms at similar temperatures.
+Low defect densities in the buffer layer are a prerequisite for obtaining good quality SiC layers during growth, although defect densities decrease with increasing distance of the SiC/Si interface \cite{shibahara86}.
+Next to surface morphology defects such as pits and islands, the main defects in 3C-SiC heteroepitaxial layers are twins, stacking faults (SF) and antiphase boundaries (APB) \cite{shibahara86,pirouz87}.
+APB defects, which constitute the primary residual defects in thick layers, are formed near surface terraces that differ in a single-atom-height step resulting in domains of SiC separated by a boundary, which consists of either Si-Si or C-C bonds due to missing or disturbed sublattice information \cite{desjardins96,kitabatake97}.
+However, the number of such defects can be reduced by off-axis growth on a Si \hkl(0 0 1) substrate miscut towards \hkl[1 1 0] by \unit[2]{$^{\circ}$}-\unit[4]{$^{\circ}$} \cite{shibahara86,powell87_2}.
+This results in the thermodynamically favored growth of a single phase due to the uni-directional contraction of Si-C-Si bond chains perpendicular to the terrace steps edges during carbonization and the fast growth parallel to the terrace edges during growth under Si rich conditions \cite{kitabatake97}.
+By MBE \cite{}, lower process temperatures than these typically employed in CVD have been realized, which is essential for limiting thermal stresses and to avoid resulting substrate bending, a key issue in obtaining large area 3C-SiC surfaces.
+In summary, the almost universal use of Si has allowed significant progress in the understanding of heteroepitaxial growth of SiC on Si.
+However, mismatches in the thermal expansion coefficient and the lattice parameter cause a considerably high concentration of various defects, which is responsible for structural and electrical qualities that are not not yet statisfactory.
+
+SiC on SiC epitaxy ...
 
 \section{Ion beam synthesis of cubic silicon carbide}
 
 \section{Substoichiometric concentrations of carbon in crystalline silicon}
 
-\section{Assumed precipitation mechanism of cubic silicon carbide in bulk silicon}
+\section{Assumed cubic silicon carbide conversion mechanisms}
 \label{section:assumed_prec}
 
+on surface ... md contraction along 110 ... kitabatake ... and ref in lindner ... rheed from si to sic ...
+
+in ibs ... lindner and skorupa ...
+
+nejim however ...
+