Structural studies of ion beam synthesized nanocrystals: diamond in SiC and SiC in diamond

SiC and diamond are semiconductor materials with unique physical properties for very promising applications for high frequencies, high power and extreme environment (radiation, high temperature). However, the possibility of doping these materials are limited and complementary to each other. Only n-doped SiC and p-doped diamond can be produced in a reliable way [1]. It is found that p-n-junctions can be formed by ion beam synthesis of buried nanocrystallites, especially diamond in SiC [2] and SiC in diamond [3].
The materials studied were 6H-SiC(0001) implanted with 1x1018 cm-2 C+ (60 keV) at 900 °C and diamond(001) implanted with 5.3x1017 cm-2 Si+ (120 … 170 keV) at 900 °C. In this high temperature implantation processes nanocrystals of diamond are grown in 6H-SiC at a depth of (110 ± 30) nm below the surface and 3C-SiC nanocrystals in diamond at a depth of (90 … 130 ± 30) nm, respectively. At lower implantation temperatures it was not possible to grow diamond in 6H-SiC.
Various x-ray scattering techniques like coplanar diffraction, grazing incidence diffraction, texture studies, measurement of specular reflectivity, and reciprocal space mapping were used at laboratory and synchrotron (ROBL at ESRF) sources to study structural details of the material.
The nanocrystals of diamond have a diameter of 5 … 6 nm, and those of 3C-SiC a diameter of 7 … 8 nm. They are oriented completely heteroepitaxially according to
diamond < 1 1 1 > || substrate 6H-SiC < 0 0 0 1 >
diamond < 1 1 0 > || substrate 6H-SiC < 1 1 -2 0 >
3C-SiC < 0 0 1 > || substrate diamond < 0 0 1 >: all crystallographic directions of both cubic materials coincide.
The mosaicity (angular fluctuation of the alignment) is anisotropic to the surface and lies for diamond crystals in 6H-SiC in the range from 2° (220) to 6° (111) and for 3C-SiC crystallites in diamond in the range from 5° (111) to 12° (002), respectively.
The heteroepitactic growth is favoured by a partial coherence of the neighbouring crystal lattices: in both systems a 4:5 coherence between the crystal lattices of synthesized crystallites and substrate is observed:
5 x ddiamond(111) » 4 x d6H-SiC(0006) (1.027 nm » 1.004 nm)
5 x ddiamond(220) » 4 x d6H-SiC(11-20) (0.629 nm » 0.615 nm)
4 x a3C-SiC » 5 x adiamond (1.744 nm » 1.780 nm).
In all cases the strain does not exceed 2.3 %.
In conclusion it can be stated that well aligned nanocrystals can be grown by the ion beam synthesis at high temperatures in 6H-SiC as well as in diamond.

References
[1] - R. Kalish, Diamond and Related Materials 10, 1749 (2001)
[2] - V. Heera, W. Skorupa, B. Pécz and L. Dobos, Applied Physics Letters 76, 2847 (2000)
[3] - V. Heera, F. Fontaine, W. Skorupa, B. Pécz and A. Barna, Applied Physics Letters 77, 226 (2000)