Overcoordinated hydrogens in the carbon vacancy: donor centers of SiC
Epitaxial silicon carbide is likely to contain hydrogen and vacancies ( V); therefore, V+nH complexes are likely to influence its electronic properties. Using ab initio calculations we show that neutral and positive H atoms are trapped by carbon vacancies ( V(C)) in three-center bonds with two Si neighbors. The double positive charge state of V(C)+H is not stable in equilibrium and in the triply positive state H binds only to one of the Si neighbors. At most two H atoms can be accommodated by a single V(C). The V(C)+nH complexes have donor character and exhibit rather atypical vibration modes for Si-H bonds. Occupation levels and spin distributions were calculated and compared for V(C)+H and V(C).
Gali
A
Department of Atomic Physics, Technical University of Budapest, Budafoki ut 8., H-1111, Budapest, Hungary.
Aradi
B
Deak
P
Choyke
WJ
Son
NT