arXiv subjects

V. G. Ralchenko

Publications and source records attributed to V. G. Ralchenko.

5 recordsLinked to original sources

arXiv2026

Near surface donor-acceptor pairs in hydrogenated homoepitaxial diamond nanolayers

Hydrogen-terminated diamond is known for its p-type surface conductivity, which arises from a near-surface hole accumulation layer induced by adsorbed acceptor species. Here, we demonstrate that these surface acceptors also form optically active donor-acceptor pairs (DAP) with substitutional nitrogen donors in diamond. The insertion of a nominally undoped CVD interlayer between a nitrogen-rich HPHT substrate and a hydrogen-terminated surface enables the precise tuning of the donor-acceptor separation with nanometer precision. Radiative DAP recombination appears as bright, spectrally narrow lines whose intensity, energy, and decay dynamics depend systematically on interlayer thickness. Individual lines show single-photon statistics, while ensembles exhibit strong polarization anisotropy reflecting the planar donor-acceptor geometry. These findings reveal an optical counterpart of hydrogen-induced surface transfer doping in diamond and establish a surface-defined, nanometer-tunable platform for engineering DAP-based quantum emitters.

quant-ph↗

arXiv2017

Uniform diamond coatings on WC-Co hard alloy cutting inserts deposited by a microwave plasma CVD

Polycrystalline diamond coatings have been grown on cemented carbide substrates with different aspect ratios by a microwave plasma CVD in methane-hydrogen gas mixtures. To protect the edges of the substrates from non-uniform heating due to the plasma edge effect, a special plateholder with pockets for group growth has been used. The difference in heights of the substrates and plateholder, and its influence on the diamond film mean grain size, growth rate, phase composition and stress was investigated. The substrate temperature range, within which uniform diamond films are produced with good adhesion, is determined. The diamond-coated cutting inserts produced at optimized process exhibited a reduction of cutting force and wear resistance by a factor of two, and cutting efficiency increase by 4.3 times upon turning A390 Al-Si alloy as compared to performance of uncoated tools.

cond-mat.mtrl-sci↗

arXiv2014

Channeling Effect in Polycrystalline Deuterium-Saturated CVD Diamond Target Bombarded by Deuterium Ion Beam

At the ion accelerator HELIS at the LPI, the neutron yield is investigated in DD reactions within a polycrystalline deuterium-saturated CVD diamond, during an irradiation of its surface by a deuterium ion beam with the energy less than 30 keV. The measurements of the neutron flux in the beam direction are performed in dependence on the target angle, \b{eta}, with respect to the beam axis. These measurements are performed using a multichannel detector based on He3 counters. A significant anisotropy in neutron yield is observed, it was higher by a factor of 3 at \b{eta}=0 compared to that at \b{eta} = +-45°. The possible reasons for the anisotropy, including ion channeling, are discussed.

physics.ins-det↗

arXiv2013

Behaviour of a muonic atom as an acceptor centre in diamond

Polarized negative muons were used to study the behaviour of the boron acceptor centre in synthetic diamond produced by the chemical vapour deposition (CVD) method. The negative muon substitutes one of the electrons in a carbon atom, and this muonic atom imitates the boron acceptor impurity in diamond. The temperature dependence of the muon spin relaxation rate and spin precession frequency were measured in the range of 20 - 330 K in a transverse magnetic field of 14 kOe. For the first time a negative shift of the muon spin precession was observed in diamond. It is tentatively attributed to an anisotropic hyperfine interaction in the boron acceptor. The magnetic measurements showed that the magnetic susceptibility of the CVD sample was close to that of the purest natural diamond.

cond-mat.mtrl-sci↗

arXiv2011

Behaviour of muonium in synthetic diamond

The probabilities of finding the muon in various states in synthetic single crystal and polycrystalline diamond were studied. In the IIa-type single-crystal sample at 150 K the contributions of the diamagnetic muon, `normal', and `anomalous' muonium were observed to be 1.5 %, 57 % and 8.1 %, respectively. The missing fraction of muon polarization was 33.4 %, which is approximately two times smaller than in the Ia-type natural diamond, and two or three times greater than in the IIa- and IIb-type natural diamonds. The muon spin relaxation rates at the `normal' and `anomalous' muonium states in the synthetic and natural samples of IIa- and IIb-type are similar.

cond-mat.other↗