Optical defect centers and surface morphology of isotopically enriched diamond layers in designer diamond anvils

Abstract

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 C13 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 320K using micro-photoluminescence (PL) spectroscopy with an argon ion and krypton laser excitation source. The defect spectra were dominated by zero phonon lines (ZPL) from nitrogen-related defect centers at nominal energies of 1.945eV (640nm defect) and 2.156eV (575nm defect), especially for the non-(100) surfaces. Polished (100) surfaces fluoresced weakly. ZPL’s at 1.77 and 1.68eV are observed, but not for all isotopically mixed samples. The 1.77eV ZPL appears to be associated from the original diamonds, while the 1.68eV 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 (100) 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.