Effect of surface defects on CVD diamond nucleation on 6H SiC

The thin SiC layer often observed between a Si substrate and a diamond film has led to the belief that the formation of this SiC layer precedes diamond nucleation. However, the nucleation of diamond on a clean, undamaged SiC surface is difficult. Some of the defects introduced by abrading the surface of many substrate materials with diamond powder before deposition appear to serve as nucleation sites. Atomic-scale defects (vacancies, interstitials) and impurities can be introduced by ion implantation. Single-crystal 6H SiC with the external face composed of Si or C were implanted with silicon (150 keV) and carbon (55 keV) ions at fluences between 2 × 10¹⁴ ions cm^-2 and 2 × 10¹⁵ ions cm^-2. Nucleation did not occur on as-received or implanted samples. Abrasion with diamond powder using an ultrasonic cleaner bath caused profuse nucleation on all samples. It was found that nucleation density on abraded samples decreased when implanted with increasing fluence of ions. Fluences of 2 × 10¹⁴ Si⁺ ions cm^-2 (150 keV) and 4 × 10¹⁴ C⁺ ions cm^-2 (55 keV) did not effect the nucleation of diamond on silicon carbide. However, a fluence of 2 × 10¹⁵ Si⁺ ions cm^-2 completely suppresses the nucleation of diamond. Rutherford backscattering spectrometry/channeling studies on the high-fluence-implanted silicon carbide sample showed the presence of an amorphous surface layer suggesting that CVD diamond does not nucleate on amorphous SiC.