Effect of surface defects on the nucleation of CVD diamond on 6H silicon carbide

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. This thesis reports the effects of abrasion and ion-implantation on the nucleation of diamond on SiC during hot-filament assisted CVD.

Single crystal 6H SIC with the external face composed of Si or C were used as substrates. Silicon (150 keV) and C (55 keV) ion were implanted at fluences between 2 x 10¹⁴/cm² and 2 x 10¹⁵/cm².

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 x 10¹⁴; Si+/cm² (150 keV) and 4x 10¹⁴ C+/cm² (55 keV) did not effect the nucleation of diamond on silicon carbide. However, a fluence of 2 x 10^{15 Si+/cm2completely suppresses the nucleation of diamond.}

RBS/channeling studies on the high fluence implanted silicon carbide sample showed the presence of an amorphous layer at the surface, thereby questioning some of the recently proposed theories about the mechanism of CVD diamond nucleation.

It is proposed that healing or smoothing of micro-flaws which are thought to act as nucleation sites, is an important mechanism to reduce the diamond nucleation density by ion implantation. Further work needs to be done to determine the exact nature of the mechanism by which ion implantation influences the nucleation of CVD diamond.