Homoepitaxial diamond layers on off-axis Ib HPHT substrates: Growth of thick films and characterisation by high-resolution X-ray diffraction

Homoepitaxial diamond films with a thickness of several hundred microns have been grown on (001)-oriented Ib HPHT substrates by microwave plasma chemical vapour deposition (MWPCVD). Systematic variation of the off-axis angle of the growth surface between 0° and 8° caused a strong increase in growth rate. In addition, it was found that vicinal angles above 6° facilitate extraordinarily stable homoepitaxial growth. They result in a complete suppression of non-epitaxial crystals for the total range of process parameters which have been studied. For very high film thicknesses, the off-axis angles and their influence on the homoepitaxial growth decrease. High-resolution X-ray diffraction (HRXRD) was used to measure the crystalline perfection of the films. By extracting the bending contribution from the total peak broadening we could distinguish different types of peak broadening behaviour in our samples. For the film that showed the highest crystalline perfection and a vanishing bending we obtained an extraordinary low line width of 0.0027°. This sample was deposited with CO2 in the gas phase.