Optical defect centers and surface morphology of isotopically enriched diamond layers in designer diamond anvils
Journal of Applied Physics
We have studied optical defect centers and surface morphology of isotopically enriched layers grown on diamond anvils by microwave plasma chemical vapor deposition for applications as designer diamond anvils in high-pressure diamond anvil cell devices. Various mixtures of methane isotopes were used to grow homoepitaxial diamond with 13 C molar fractions of 0.01, 0.41, 0.83, and 0.99 as determined from Raman spectroscopy. Defect centers were studied at temperatures between 80 and 320 K using
... o-photoluminescence ͑PL͒ spectroscopy with an argon ion and krypton laser excitation source. The defect spectra were dominated by zero phonon lines ͑ZPL͒ from nitrogen-related defect centers at nominal energies of 1.945 eV ͑640 nm defect͒ and 2.156 eV ͑575 nm defect͒, especially for the non-͑100͒ surfaces. Polished ͑100͒ surfaces fluoresced weakly. ZPL's at 1.77 and 1.68 eV are observed, but not for all isotopically mixed samples. The 1.77 eV ZPL appears to be associated from the original diamonds, while the 1.68 eV ZPL is known to originate with silicon-based defects. Atomic force microscopy of as-grown isotopically enriched layers show rough growth steps in areas with surface roughness of hundred nanometers and smooth areas with surface roughness of few nanometers. Our studies indicate that ͑100͒ polished surfaces of isotopically enriched designer diamonds with low concentration of nitrogen defect centers can be fabricated for a variety of applications in high pressure research.