Diamond (111) homoepitaxy via hot-filament chemical vapor deposition: Growth mode, transition metal incorporation, and twin formation

This study investigates the relationship between growth mode and Ta incorporation in diamond (111) homoepitaxial growth via hot-filament chemical vapor deposition (HFCVD) with Ta filaments. Increasing methane concentration from 0.35 % to 1.4 % caused a transition from two-dimensional island growth to three-dimensional growth, while simultaneously decreasing Ta concentration in the HFCVD films from 10 20 atoms/cm 3 to 10 19 atoms/cm 3 . Flux analysis revealed that the sticking coefficient of Ta remained nearly constant regardless of growth mode, indicating that Ta incorporation is primarily determined by the Ta/C ratio in the gas phase rather than surface morphology. Notably, a high density of rotational twins, a phenomenon characteristic of HFCVD and rarely observed in microwave plasma CVD, was observed in two-dimensional island growth. Strikingly, the areal density of these twins (2 × 10 8 /cm 2 ) is found to be four orders of magnitude lower than that of the incorporated Ta atoms (2 × 10 12 atoms/cm 2 ). This significant discrepancy suggests that twin formation is a complex process not triggered by the simple incorporation of individual Ta atoms. These findings provide a new framework for understanding metal-induced defect formation and are crucial for the development of large-area, high-quality diamond wafers. • Growth mode can be controlled via methane concentration in HFCVD. • 2D island growth of diamond (111) is achieved despite high Ta concentration. • Ta incorporation in HFCVD diamond is controlled by the gas-phase Ta/C ratio. • A high density of rotational twins is characteristic of HFCVD on diamond (111). • Twin density is four orders of magnitude lower than incorporated Ta atom density.