Homoepitaxial single crystal diamond layers with bright photoluminescence (PL) of silicon-vacancy (SiV) color centers at 738 nm wavelength have been grown on (100) diamond substrates by a microwave plasma CVD using a controlled Si doping via adding silane to CH 4 -H 2 reaction gas mixture in the course of the deposition process. In the range of the silane concentrations SiH 4 /CH 4 explored, from 0 to 2.4%, the SiV PL intensity shows a nonmonotonic behavior with silane addition, with a maximum at 0.6%SiH 4 /CH 4 , and a rapid PL quenching at higher Si doping. The maximum SiV concentration of %450 ppb in the samples has been determined from optical absorption spectra. It is found that the SiV PL intensity can strongly, an order of magnitude, increase within non-epitaxial inclusions in single crystal diamond film.
Silicon-vacancy
(SiV–) color center in diamond
is of high interest for applications in nanophotonics and quantum
information technologies, as a single photon emitter with excellent
spectral properties. To obtain spectrally identical SiV– emitters, we doped homoepitaxial diamond films in situ with 28Si, 29Si, and 30Si isotopes
using isotopically enriched (>99.9%) silane SiH4 gas
added
in H2–CH4 mixtures in the course of the
microwave plasma-assisted chemical vapor deposition process. Zero-phonon
line components as narrow as ∼4.8 GHz were measured in both
absorption and luminescence spectra for the monoisotopic SiV– ensembles with a concentration of a few parts per billion. We determined
with high accuracy the Si isotopic energy shift of SiV– zero-phonon line. The SiV– emission intensity
is shown to be easily controlled by the doped epifilm thickness. Also,
we identified and characterized the localized single photon SiV– sources. The developed doping process opens a way
to produce the SiV– emitter ensembles with energy
confined in an extremely narrow range.
The effect of isotopic modification of diamond lattice on photoluminescence (PL) and optical absorption spectra of ensembles of SiV À centers was studied. Thin epitaxial diamond layers were grown by a microwave plasma CH 4 /H 2 mixtures using methane enriched to 99.96% for either 12 C or 13 C isotopes, while the Si doping was performed by adding a small percentage of silane SiH 4 into the plasma. Temperature dependent SiV À ZPL spectra in absorption were measured at 3-80 K to monitor the evolution of the ZPL fine structure. It is found that the SiV À ZPL at 736.9 nm observed in PL for 12 C diamond at T ¼ 5 K, exhibits a blue shift of 1.78 meV, to 736.1 nm in 13 C diamond matrix. Narrow ZPL with the width (FWHM) of 0.09 meV (21 GHz) was measured in absorption spectra at T ¼ 3-30 K in the Si-doped 13 C diamond. Besides the charged SiV À center, the absorption of the neutral SiV 0 defect at 946 nm wavelength has also been detected. From changes observed in SiV À phonon band structure in PL with isotopic modification, the band at 64 meV was confirmed to be a local vibration mode (LVM) involving a Si atom.
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