Effects of crystallographic orientation on the homoepitaxial overgrowth on tiled single crystal diamond clones

• Off-direction optimization improved crystal quality.
• Off-direction optimization suppressed single-crystal diamond wafer cracking.
• Quality improved by growing 1 mm layers rather than 0.1 mm layers

We found that optimization of the off-direction could be used to control morphology, improve crystal quality and suppress the breaking of single crystal diamond tiled-wafers. The dependence of the full width at half maxima of the Raman spectra on the angle made by the off-direction and the edges of constituent substrates as well as the thicknesses of the wafers were studied. Results suggest that better quality is obtained when the off-direction is perpendicular to the edges compared with the non-perpendicular cases. The crystal quality of the boundaries of the constituent substrates is maintained or even improved upon additional growth. However, the crystal quality of the interior region degrades. We also found that a misalignment of the off-direction against the edges could suppress cracking. This especially occurs in crystals that are larger than 1 in. in size. The mechanisms responsible for these improvements are discussed.