MICROSTRUCTURE AND GROWTH OF MWCVD DIAMOND ON SI1-XCX BUFFER LAYERS

The microstructure of Si1-xCx buffer layers grown by molecular beam ep itaxy on (001)-oriented silicon and the influence on the growth of dia mond by microwave-assisted chemical vapour deposition on these layers were investigated for high and low carbon fractions x of 3.5 and 1.4%. For x = 3.5% microtwins were observed by transmission electron micros copy in the buffer layer before and after diamond growth. For x = 1.4% formation of extended defects was absent. During diamond deposition s mall crystalline beta-SiC precipitates were generated that are homogen eously distributed in the buffer layer. Lattice parameter measurements by high-resolution X-ray diffraction indicate a decrease of the subst itutional carbon concentration from 1.4 to 0.7% during diamond deposit ion. Investigations of the structure of the interface between diamond and the buffer layer by high-resolution transmission electron microsco py in (110)-crystal projections show small regions of diamond grains i n direct contact with the buffer layers and also regions of contact be tween diamond and a thin epitaxial oriented beta-SiC interlayer. The o rientation relationships between the lattices of diamond grains and bu ffer layers are characterized by small and large tilts of, e.g., 4 and 76 degrees, respectively. (C) 1997 Elsevier Science S.A.