-the stoichiometric composition of silicon and carbon
-is the only stable compound in the C/Si system.
-SiC is a mainly covalent material in which both,
-the Si and C atom are sp3 hybridized.
-the local order of the silicon and carbon atoms
-characterized by the tetrahedral bond is always the same.
-however, more than 250 different polytypes exist,
-which differ in the one-dimensional stacking sequence of
-identical, close-packed SiC bilayers,
-which can be situated on one of three possible positions (abbreviated a,b,c).
-the stacking sequence of the most important polytypes is displayed here.
-the 3c polytype is the only cubic polytype.
-
-different polytypes exhibit different properties,
-which are listed in the table
-and compared to other technologically relevant semiconductor materials.
-despite the lower charge carrier mobilities for low electric fields,
-SiC clearly outperforms silicon.
-among the different polytypes, the cubic phase shows the highest
-break down field and saturation drift velocity.
-additionally, these properties are isotropic.
-thus, the cubic polytype is considered most effective for highly efficient
-high-performance electronic devices.
-
-slide 4
-
-SiC is rarely found in nature and, thus, must be synthesized.
-it was first observed by moissan from a meteor crater in arizona.
-the fact that natural SiC is almost only observed
-as individual presolar SiC stardust grains near craters of meteorite impacts
-already indicates the complexity involved in the synthesis process.
-
-however, nowadays, much progress has been achieved in thin film growth
-by molecular beam epitaxy and chemical vapor deposition.
-indeed, commerically available semiconductor devices based on alpha SiC exist,
-although these are still extremely expensive.
-however, production of the advantageous cubic type is less advanced,
-mainly due to the
-mismatches in the thermal expansion coefficient and the lattice parameter
-(with respect to the substrate)
-which cause a considerable amount of defects,
-that is responsible for structural and electrical qualities
-that are not yet satisfactory.
-
-next to CVD and MBE, the ion beam synthesis technique, which consists of
-high dose ion implantation followed by a high-temperature annealing step
-turned out to constitute a promising method to form buried layers of SiC in Si
-as indicated in this sketch.
-due to the high areal homogenity achieved in ibs
-the size is only limited by the beam scanning equipment
-and sythesized films do not exhibit surface bending effects
-in contrast these formed by cvd and mbe.
-this enables the synthesis of large are SiC films.
-
-slide 5
-
-the ibs synthesis of SiC was extensively investigated and optimized
-here in augsburg in the group of joerg lindner.
-a two-step implantation process was suggested.
-the trick is to destroy stable precipitates at the layer interface
-by implanting a remaining low amount of the dose at lower temperatures
-to enable redistribution of the C profile during annealing,
-which results in a homogeneous SiC layers with a sharp interface
+one method to fabricate 3C-SiC, the cubic phase of SiC, is ibs,
+i.e. high dose ion implantation followed by a high-temperature annealing step,
+this was extensively investigated here in augsburg in the group of j lindner.
+an optimized two-step implantation process was suggested.
+the trick is to destroy stable precipitates
+that formed at the layer interface during the first implantation step
+by implanting a low remaining amount of the regular dose at lower temperatures.
+this enables redistribution of the C atoms during annealing,
+which results in a homogeneous SiC layer with a sharp interface