basic stuff, now lindner ...

diff --git a/bibdb/bibdb.bib b/bibdb/bibdb.bib
index 56041df..b2b9c19 100644 (file)
--- a/bibdb/bibdb.bib
+++ b/bibdb/bibdb.bib
@@ -1223,6 +1223,7 @@
   doi =          "10.1557/PROC-354-171",
   URL =          "http://dx.doi.org/10.1557/PROC-354-171",
   eprint =       "http://journals.cambridge.org/article_S1946427400420853",
+  notes =        "first time ibs at moderate temperatures",
 }
 
 @Article{lindner99,
@@ -4111,4 +4112,3 @@
   URL =          "http://link.aip.org/link/?JAP/77/2978/1",
   doi =          "10.1063/1.358714",
 }
-

diff --git a/posic/thesis/sic.tex b/posic/thesis/sic.tex
index ca9aded..7228cbe 100644 (file)
--- a/posic/thesis/sic.tex
+++ b/posic/thesis/sic.tex
@@ -245,11 +245,17 @@ Since no amorphous or polycrystalline regions have been identified, twinning is
 
 Further studies revealed the possibility to form buried layers of SiC by IBS at moderate substrate and anneal temperatures \cite{lindner95}.
 Different doses of C ions with an energy of \unit[180]{keV} were implanted at \unit[330-440]{$^{\circ}$C} and annealed at \unit[1200]{$^{\circ}$C} or \unit[1250]{$^{\circ}$C} for \unit[5-10]{h}.
-For a critical dose, which was found to depend on the orientation of the Si substrate, corresponding to a \unit[50]{at.\%} C concentration at the implantation peak, C atoms get redistributed appropriately resulting in the formation of a stoichiometric buried layer of SiC exhibiting a well-defined interface to the Si host matrix.
-Redistribution of the excess C in case of overstoichiometric implantations is not observed.
-Higher implantation energies were found to result in layers of variable composition exhibiting randomly distributed SiC precipitates.
-
-high t -> direct SiC formation -> no redistribution ...
+For a critical dose, which was found to depend on the Si substrate orientation,  the formation of a stoichiometric buried layer of SiC exhibiting a well-defined interface to the Si host matrix was observed.
+In case of overstoichiometric C concentrations the excess C is not redistributed.
+These investigations demonstrate the presence of an upper dose limit, which corresponds to a \unit[50]{at.\%} C concentration at the implantation peak, for the thermally induced redistribution of the C atoms from a Gaussian to a box-shaped depth profile upon annealing.
+For higher concentrations the formation of strong C-C bonds is expected.
+Increased temperatures are necessary for the dissociation of these C clusters.
+Furthermore, higher implantation energies were found to result in layers of variable composition exhibiting randomly distributed SiC precipitates.
+In another study \cite{serre95} high dose C implantations were performed at room temperature and \unit[500]{$^{\circ}$C} respectively.
+Implantations at room temperature lead to the formation of a buried amorphous carbide layer in addition to a thin C-rich film at the surface, which is attributed to the migration of C atoms towards the surface.
+In contrast, implantations at elevated temperatures result in the exclusive formation of a buried layer consisting of 3C-SiC precipitates epitaxially aligned to the Si host, which obviously is more favorable than the C migration towards the surface.
+Annealing at temperatures up to \unit[1150]{$^{\circ}$C} does not alter the C profile.
+Instead defect annihilation is observed and the C-rich surface layer of the room temperature implant turns into a layer consisting of SiC precipitates, which, however, are not aligned with the Si matrix indicating a mechanism different to the one of the direct formation for the high-temperature implantation.
 
 ..  lindner limit in dose -> 1250
 ... two temp implantation ... sharp interface