Freestanding 30 mm square {111} twin-free heteroepitaxial diamonds grown on highly-misoriented {0001} sapphire substrates

Abstract Freestanding 30 mm square twin-free {111} diamond films were obtained by heteroepitaxial growth on highly misoriented sapphire substrates. X-ray rocking curve revealed high crystal quality of the diamond with full width at half maximum of 94 arcsec for {111} plane. X-ray pole figure of {220} diffraction peaks exhibited threefold symmetry, suggesting the single crystallinity without twinning. Results of systematic investigation of off-angle and off-direction dependencies demonstrated that large misorientation toward 〈11-20〉 of {0001} plane sapphire substrate not only promotes step-flow growth but also suppresses twin formation by aligning 〈11-2〉 step direction of {111} diamond.