Structural defects in homoepitaxial diamond layers grown on off‐axis Ib HPHT substrates

In the present study homoepitaxial diamond films have been grown by microwave plasma chemical vapour deposition (MWPCVD) on (001)‐oriented Ib HPHT substrates with off‐axis angles of up to 11°. Freestanding films of several hundred microns thickness were produced by removal of the Ib substrate and of the polycrystalline rim. In high resolution X‐ray diffraction (HRXRD) rocking curve measurements the crystals showed a full width at half maximum (FWHM) between (2 × 10 –3 )°, which is close to the instrumental limit of our setup, and maximum values of (3 × 10 –2 )°. The structural quality is directly reflected in the strength of the birefringence observed in the optical microscope. While the high quality sample showed a weak birefringence with a couple of localized centres distributed over the whole sample surface, a tatami‐like pattern is measured for the sample with the broad rocking curve. Identical defect structures with perfect correspondence are observed in X‐ray topography images. Furthermore the X‐ray topographs allow to identify isolated dislocation lines. Both characterisation methods show that the defect lines are aligned along the off‐axis direction which allows conclusions on the mechanism of formation. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)