Pre-planting amorphous carbon films based on Ir composite substrates for diamond nucleation

•The relative content of sp2 and sp3 carbon were controlled effectively by varying the energy of the carbon source.•Deposition of the amorphous carbon film increases the nucleation density by nearly an order of magnitude.•Amorphous carbon films deposited at 9 Hz had the highest content of sp3 hybridized bonds and overall order.•Pre-planting amorphous carbon films reduces the energy required for BEN nucleation and decreases damage to Ir films. A tunable locally ordered amorphous carbon layer was pre-implanted on the iridium (Ir) composite substrate using a multi-excitation source plasma coating system. The nucleation interface was mainly studied by scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The results show that by designing and modulating the content and ordering of sp2/sp3 hybridized carbon bonds in the amorphous carbon on the surface of Ir thin films, an overall ordered diamond nucleation layer was obtained. When the pulse frequency of the carbon source was regulated to 9 Hz, the (100) diamond grains were uniformly aligned without the appearance of twins after 4 h of growth, and the nucleation density was 7.5 × 109 cm−2, which was subsequently expected to obtain single-crystal diamond by grain boundary annihilation. Based on the Ir-amorphous carbon pre-growth layer, it can accelerate the dissolution-precipitation process of carbon ions into the Ir film to form a supersaturated solid solution during the bias nucleation, and increase the nucleation sites, which is of great significance for improving the nucleation density of large-size single-crystal diamond heterogeneous epitaxy.