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12LS-P-10
LASER SYSTEMS AND MATERIALS
ALT'22
Growth of nanocrystalline CVD diamond films doped with germanium
A. Martyanov, V. Sedov, I. Tiazhelov
Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow Main author email address: [email protected]
Color centers in diamond have unique spectral characteristics: high brightness and stability at room temperature, quantum efficiency, short photoluminescence (PL) decay times, and narrow PL lines, which are which are in demand for nanophotonics and quantum optics [1]. Nitrogen-vacancy (NV) and silicon-vacancy (SiV) color centers are the most actively studied. Germanium-vacancy (GeV) color centers in diamond (discovered in 2015) are less studied. They have a narrow zero-phonon line in the photoluminescence spectra at X = 602 nm [2].
In this work, polycrystalline diamond films were doped with nitrogen and germanium at the same time. Diamond films were deposited in the microwave plasma CVD system ARDIS-100 (2.45 GHz). Polished single-crystal silicon wafers were seeded in a water-based slurry of detonation nanodiamond with an average particle size of 5 nm. Diamond was deposited under the following parameters: gas mixture pressure 100 Torr, microwave power 5 kW, substrate temperature 850°C. The film thickness was controlled in-situ with a laser interferometer technique. For correct comparison of the films obtained at different process parameters, their thickness was kept always the same 2 p,m.
Even small additions of nitrogen to the reactor during CVD diamond synthesis stimulate the secondary nucleation of diamond and lead to the formation of nanocrystalline films (NCD) instead of standard microcrystalline (MCD) (fig.1). Therefore, an alternative method of stimulating secondary nucleation was also used: increasing the methane concentration (up to 20%) [3].
Wavelength
Fig. 1. Photoluminescence spectra of polycrystalline diamond films doped with germanium: MCD at 4% CH4; NCD with nitrogen addition or with increased methane concentration up to 20%.
It was found that a change in the structure of diamond with an increase in methane concentration leads to a 50-fold increase in the intensity of GeV centers. At the same time, a change in the structure of diamond with the addition of nitrogen or air completely quenches the photoluminescence of GeV and SiV.
The work was supported by the Russian Science Foundation, Grant No. 21-72-10153.
[1] I. Aharonovich. E. Neu, Diamond nanophotonics, Advanced Optical Materials, vol. 2, pp. 911-928, (2014).
[2] V. Sedov, et. al., Growth of polycrystalline and single-crystal CVD diamonds with bright photoluminescence of Ge-V color centers using germane GeH4 as the dopant source, Diamond and Related Materials, vol. 90, pp. 47-53, (2018).
[3] V. Sedov, et. al., Deposition of diamond films on Si by microwave plasma CVD in varied CH4-H2 mixtures: Reverse nanocrys-talline-to-microcrystalline structure transition at very high methane concentrations, Diamond and Related Materials, vol. 109, p. 108072, (2020).
