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We investigate the propagation of laser-induced hypersound waves in polycrystalline diamond films by analyzing the spatial changes in the phase and amplitude of the probing laser beam reflected from the surface. We show that the velocity of bulk (longitudinal) acoustic waves is 14300 m/s in films with an average crystallite size of ≈ 0.2 μm and monotonically increases to 17200 m/s with increase in the crystallite size up to ≈ 2 μm. For surface waves, anomalous dispersion is observed, leading to a change in the phase velocity from ≈ 4800 to ≈ 6600 m/s, which is explained by the effective localization of the surface wave field in the diamond films. The values obtained can be used for the design of diamond films and membranes for applications in diamond photonics and acousto-electronics.

We produced microcrystalline diamond coatings with nanocrystalline top diamond layer on WC-Co cutting inserts in a microwave plasma (2.45 GHz) chemical vapor deposition reactor. The coatings have a high uniformity of the substrate surface owing to elimination of the plasma edge effect by application of a moveable quartz ring above the substrate holder. Computer modeling showed how the positioning of the ring changes the electromagnetic field around the substrates. A new approach was used to stabilize the temperature of the cutting inserts during the coating process, which is based on in situ control of the quartz ring position by proportional-integral-differential (PID) regulation. The coatings have been characterized with microRaman spectroscopy in a mapping mode in cross section of the samples. Depth profiles of diamond Raman peak position and width are demonstrated and the stress in the films is estimated, the minimum stress being determined for the cutting insert apex.

Diamond coatings on hard alloy tools produced by chemical vapor deposition (CVD) from methane-hydrogen mixtures greatly enhance the functional properties such as wear resistance and quality of the material processing. By varying the gas composition during the diamond film growth it is possible to cyclically change the film structure between microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) to produce MCD/NCD multilayers that improves the mechanical properties of the film and reduces its stress and roughness. As the diamond growth occurs with participation of radicals generated in the plasma thermo-chemical reactions it is important to control in situ the presence of those species and gas temperature Tg. Here we used optical emission spectroscopy (OES) to monitor atomic hydrogen, CN, CH and C2 dimer radicals in course of deposition of MCD/NCD coatings by microwave plasma CVD in CH4-H2 and CH4-N2-H2 mixtures. The gas temperature has been calculated from analysis of rotational components of structure of C2(Δν = 0) emission line. We found that addition of nitrogen (4%) in CH4-H2 plasma, which is needed to form NCD, significantly, by about 500 K reduces Tg (from Tg = 3910 K to Tg = 3330 K). We developed an algorithm tolerable to small shifts of the measured spectral lines which provided fast calculation of Tg, so that the spectrum record and the automatic processing of fine structure of C2(Δν = 0) line totally take the time of about 5 min.

The high efficiency of double-crystal X-ray diffractometry and topography methods in the characterization of crystals during refinement of the crystal-growth technology is demonstrated for the example of diamond bulk crystals and films obtained by the high pressure, high temperature method and by chemical vapor deposition, respectively. Techniques and study schemes for analysis of the real crystal structure, assessment of the chemical composition and the period of the crystal lattice, and analysis of the distinctive features of the deformation and thickness of thin films are described. Major structural defects (dislocations, stacking defects, inclusions of a different phase, and others) that emerge during the production of synthetic diamond crystals are identified.

A polycrystalline diamond film is grown on a 2 inch Si substrate using a microwave-plasma chemicalvapor-deposition technique. The high quality of the diamond films is confirmed by Raman spectra. A multiple-step procedure is used for local etching of the substrate to form the pattern of an array of 50 diamond membranes with the diameter in a range from 150 to 300 μm. The morphology of the membranes is examined using scanning electron microscopy. The membranes obtained can be used as the base material for the fabrication of pressure sensors, X-ray detectors and scintillators, and in quantum optics as optical resonators for single-color centers in diamond.

Thermal conductivity [Formula: see text] of single-crystal CVD diamond lightly doped (about 3 ppm) with nitrogen has been measured at temperatures from 5.7 to 410 K. The sample was carefully characterized by optical absorption and photoluminescence spectroscopy for the presence of impurities. Nine different optically active defects related with nitrogen, hydrogen, and silicon impurities have been identified and quantified. This pink-tint crystal showed a high thermal conductivity of [Formula: see text] W cm[Formula: see text] K[Formula: see text] at room temperature, which is very close to the highest value ever measured at about 25 W cm[Formula: see text] K[Formula: see text] for diamonds of natural isotopic composition. At the same time, the [Formula: see text] of the crystal showed strong suppression [Formula: see text]% at temperatures [Formula: see text] K with a maximum decrease of 2.7 times at [Formula: see text] K compared to high purity diamonds. This behavior of the conductivity is attributed to a phonon scattering by charge carriers bound to nitrogen-related impurity centers, which is ineffective, however, at room and higher temperatures. The [Formula: see text] has been calculated within the model based on the Callaway theory taking into account the elastic phonon scattering off charge carriers (holes and electrons) in the ground states of doping centers, and a very good agreement between the measured and theoretical data has been achieved. The model also gives a good approximation to the experimental data for [Formula: see text] given in the literature for synthetic and natural single-crystal diamonds.

The conductivity of epitaxial diamond films lightly doped with boron has been studied at strong electric fields up to ~5 × 105 V/ cm. It is shown that field ionization of boron acceptors in diamond at room temperature, because of the low concentration of free holes and the high binding energy of boron, occurs due to the Frenkel–Poole effect.

Homoepitaxial diamond growth may proceed with stops and resumptions to produce thick (a few millimeters or even larger) crystals or structures with different layers (e.g., doped and intrinsic diamonds). Here, we studied the effect of interrupting and resuming the growth of single crystal diamond films by microwave plasma CVD in CH4–H2 mixtures, with a focus on the change in the surface morphology with the process time. We found a strong impact of the transition period from a pure H2 plasma to a steady state gas composition on the surface relief evolution. The growth resumption starting from a well-ordered step structure is shown to proceed via the destruction of the steps with further recovery. The velocity of the step propagation, ∼32 μm h−1, was determined from the comparison of the step pattern images obtained after each short (30 min) deposition period. For epitaxy on a polished substrate surface, we observed the growth rate retarding very early in the process stage presumably because of the incomplete macroscopic step formation. Using photoluminescence (PL) mapping in the cross-sections of a multilayer epi-film, the depth profiles of silicon-vacancy (SiV) and nitrogen-vacancy (NV) PL intensities were found to show a modulation correlated with the growth history. These results shed light on the origin of defects on inner interfaces in diamond crystals grown in halt-resumption mode.

The formation mechanisms of the zero-phonon line optical center at 580 nm (H19 center) in photoluminescence spectra of irradiated natural diamonds and those deposited from the vapor phase were studied after their hightemperature vacuum annealing. The photoluminescence band intensity of the H19 center was shown to increase exponentially as the annealing temperature increased. Temperature dependences of photoluminescence spectra and local mechanical stress effects on the position and full width at half-height of the 580-nm zero-phonon line optical peak led to the conclusion that the H19 optical center was a complex intrinsic vacancy defect. The work was financially supported by the Russian Science Foundation (Project 18-72-00076). Изучены механизмы формирования оптического центра с бесфононной линией (БФЛ) на 580 нм (центр Н19), проявляющегося в спектрах фотолюминесценции (ФЛ) радиационно-модифицированных природных и осажденных из газовой фазы алмазов после их высокотемпературного отжига в вакууме. Показано, что амплитуда полосы ФЛ центра Н19 экспоненциально возрастает по мере повышения температуры отжига. Из исследований температурной зависимости спектров ФЛ и влияния локальных механических напряжений на положение и ширину на полувысоте пика БФЛ 580 нм сделан вывод, что оптический центр H19 является сложным собственным вакансионным дефектом.

The real structures of epitaxial CVD films of germanium and diamond have been comparatively analyzed. The influence of the specific features of elastic-stress distribution in two-layer structures on the relaxation processes and dislocation distribution are considered. The influence of inhomogeneous (over thickness) plastic deformation, caused by the motion of dislocations under alternating elastic-stress field, on the formation of residual bending of substrates and films is shown by the example of epitaxial germanium structures. A significant difference in the relaxation processes in CVD films of diamond and germanium (crystallographic analog of diamond) is revealed.

The Diamond-NaGdF 4 : Eu and Diamond-YAG: Ce film composites were produced by chemical vapor deposition to be used as a source of intensive photo- and X-ray luminescence for radiation monitoring screens.

Nanocrystalline diamond (NCD) films were grown on the High Pressure High Temperature (HPHT) (110) single crystal (SC) diamond substrates by Microwave Plasma Enhanced Chemical Vapor Deposition (MPCVD) in methane/hydrogen/nitrogen plasma. The thickness of the films was varied between 2.2 and 22.5 μm. The cauliflower-like surface morphology was observed by means of Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). The scaling behavior of NCD films growth was investigated. The relatively high value of the roughness exponent αs = 1.5–1.6 was found indicating anomalous scaling. Therefore, shadowing and diffusional instabilities can affect the film growth. The tribological properties of the NCD films deposited on the SC(110) diamond were compared with the NCD films prepared on the Si(100) substrates. Both types of specimens were tested under similar Hertzian contact pressure. The lower wear volume losses were observed on the NCD/SC(110) specimens. Therefore, the influence of substrate and substrate/film interface properties on the tribological behavior of the NCD films grown on Si(100) can be expected to cause NCD films deflection.

Germanium-Vacancy (Ge-V) color center in diamond possesses a narrow band photoluminescence (PL) emission in the orange spectral range interesting as a single-photon source for quantum optical technologies and thermometry, therefore, development of methods for the controllable doping of diamond with Ge is of high importance for such applications. Here, we report on the synthesis of polycrystalline and epitaxial single crystal Ge-doped films using microwave plasma chemical vapor deposition (CVD) technique by addition of the germane GeH4 gas into the H2-CH4 plasma. It is demonstrated, that GeH4 addition affects the CVD growth of microcrystalline diamond, reducing the film growth rate and increasing the average diamond grain size. The films show bright photoluminescence of Ge-V centers at ≈602 nm under the optimized GeH4 concentration, with a zero-phonon line width of 1.6 nm (FWHM) for Ge-V ensemble at low temperatures (5 K). The developed in-situ doping from the germane gas opens a way for a better control of the Ge-V color center formation in diamond for photonic applications.

The luminescent diamond composite with high-intensity narrow-band X-ray luminescence at a wavelength of 612 nm with 6.2 nm width at half-height was developed. In the luminescence spectra of composites, compared with the initial powders, there are no transitions with 5D1 and 5D0 -7F4 transitions. The ratio of line intensities between the 5D0-7F1 and 5D0-7F2 transitions has changed. In the composite, the intensity of the induced electric dipole transition of 5D0-7F2 with respect to the intensity of the magnetic dipole transition of 5D0-7F1 was much larger than in the initial powder. This was indicated about a decrease in the local symmetry of the Eu3+ ions environment in the composite. The positions and intensities of individual lines in the 5D0-7F2 transition had changed markedly in the composite, in particular, the most intense line of this transition has shifted from 616 to 612 nm. This was indicated as a change in the structure of NaGdF4: Eu upon composite production. X-ray luminescence spectra of a composite with different amounts of dispersed droplets were showed that the sample with 3 droplets of dispersion with a total concentration of applied particles of 96 mg/ml was exhibited the most intense luminescence. A sample with a 65 mg/ml total concentration (1 drop of dispersion) slightly exceeds the intensity of the sample with a total concentration of 64 mg/ml (2 drops of dispersion). The lowest intensity was recorded for a sample with a 32 mg/ml total concentration (1 drop of dispersion). The concentration dependence of the intensity of X-ray luminescence from the number of dispersed particles was noted. The use of β-NaGdF4: Eu nanopowders instead of europium oxide and europium fluoride made it possible to obtain high-intensity luminescence with a higher aspect ratio of signal-to-noise ratio than previously published by various authors. The possibility of using a fluorescent diamond-fluoride composite as a X-ray luminescent screen has been shown for the first time. ACKNOWLEDGEMENTS The work was supported by grant Russian Foundation for Basic Research No. 16-29-11784-ofi. The results were obtained using the equipment of the Collective Use Centers of the Prokhorov General Physics Institute of the Russian Academy of Sciences and Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences.

(m–i–p)-Structures with high-resistance epitaxial i-layers are fabricated on heavily doped p+-type substrates with platinum contacts. The structures are studied using several methods: optical and electron microscopy and luminescence, and electrophysical (C–V and I–V characteristics) methods and tested as detectors of ionizing radiation. It is shown that the (m–i–p)-structures are promising for development of several electronic devices (high-voltage diodes, detectors of ionizing radiation, and photovoltaic devices).

The frictional coefficients at the front and rear surfaces of a VK6 hard-alloy cutter with experimental nano- and microcrystalline CVD diamond coatings applied in microwave plasma are determined by extrapolation to zero cut-layer thickness. It is found that, for diamond coatings with a single microcrystalline layer and those with both a microcrystalline layer and a nanocrystalline layer, the frictional coefficients are less than for an uncoated hard-alloy cutter and also for a cutter with a Sandvik diamond coating.

Resistance of a water-cooled polycrystalline diamond window is experimentally studied in the beam of the 10-kW fiber laser. The irradiated zones are 4 and 0.4 mm in diameter. It is shown that the transmitted beam is not distorted when the power density increases to 7 MW cm−2. It is found out that the temperature difference of a few hundreds of degrees between the center of the diamond window and its water-cooled edge does not deteriorate the distribution quality of the laser beam transmitted through the window, which allows the arising thermal lens to be corrected.

A Raman laser based on a synthetic diamond crystal pumped by nanosecond pulses of a 1030-nm Yb : YAG laser and emitting in the IR region at the first and second Stokes wavelengths of 1194 and 1419 nm, respectively, was developed. The conversion efficiency was 34 % with a slope efficiency of 50 % and an average power of 1.1 W at a wavelength of 1194 nm; the average power at 1419 nm was 0.52 W. Frequency doubling of the first Stokes component in a nonlinear BBO crystal resulted in orange (597.3 nm) radiation with a pulse energy of 0.15 mJ, an average power of 0.22 W, and a maximum efficiency of 20 %.

Generally growth surfaces of polycrystalline microwave plasma enhanced chemical vapor deposited (MPCVD) diamond are very rough in nature. So, it is necessary to planarize the surface in order to use them in different industrial applications. High quality polycrystalline diamond (PCD) has been grown by MPCVD process and afterwards the as grown surfaces of these diamonds were polished by mechanical and/or chemo mechanical techniques. The samples were characterized for roughness by non-contact profilometer, quality by Raman spectral analysis and surface morphology by SEM images. It is concluded that mechanical polishing alone can reduce the roughness if correct combination of abrasives are selected.

Chemical vapor deposited (CVD) diamonds have been irradiated with fast reactor neutrons at fluencies F = 1·1018 and 3 · 1018 cm-2 and then heated at temperatures up to 1600 °C. The processes of annealing in and annealing out of various complexes of intrinsic defects responsible for vibrational and electron-vibrational bands in the IR absorption spectra have been studied in detail. Some tens of local vibrational modes and zero-phonon lines with rather small width caused by numerous complexes of intrinsic defects were observed in the 400-11000 cm-1 range.

We report on the optical properties of He-related color centers created by He-ion implantation and subsequent thermal annealing in natural diamonds, including the temperature (300–700 K) and excitation power (1–1800 kW/cm2)-dependent photoluminescence (PL) measurements. The prospects for the use of He-implanted diamonds for temperature sensing are discussed. The effect of fast neutron irradiation on the optical properties of Si-V color centers in CVD diamonds were also examined.

We fabricated neutron detectors based on thin epitaxial CVD diamond films grown on single crystal diamond substrates, with a buried graphitic electrode produced by ion implantation and annealing. The spectra of 5.5 MeV alpha particles were measured with ≈ 3.5% energy resolution, and, based on the features of those spectra, a precise assessment of the film thickness was able achieved. A 10 μ m thick detector was tested for 252 Cf neutron and γ -radiation source, using 10 B and 6 Li isotopes as converters. Due to the small film thickness the contribution from the γ -quanta background to the spectra was restricted by energies below 200 keV, and could be easily discriminated from the neutron related signals. The performance of the detectors was tested for 5.5 MeV α -particles at fluences up to 1 0 9 cm − 2 , and no detrimental polarization effect was observed for the best sample.

The kinetic characteristics and temperature quenching of the luminescence of optical centers of silicon vacancies (SiVs) in diamond films grown in microwave plasma on substrates of aluminum nitride and synthetic diamond are investigated via laser excitation at a wavelength of 640 nm.

Micro- and nanocrystalline uniform diamond coatings with barrier tungsten layers for improved adhesion were deposited in a microwave plasma from methane-hydrogen mixtures on cemented carbide WC–6% Co substrates with high aspect ratios. Dynamic study of cutting forces and sliding friction has shown a significant improvement in the tribological properties of diamond-coated tools in cutting highly abrasive materials, such as A390 silumin and carbon-carbon composites. Confocal Raman spectrometry has been used to examine the features of wear mechanism in nano- and microcrystalline diamond coatings deposited in a microwave plasma.

Single- and multilayer coatings of micro- and nanocrystalline diamond were deposited on tungsten carbide substrates (WC + 6 wt.% Co alloy) in a microwave plasma of methane/hydrogen and methane/hydrogen/nitrogen mixtures. Barrier tungsten layers were used to improve adhesion of the diamond coatings to the substrates. Raman spectroscopy was used to study the properties of the nano- and microcrystalline diamond coatings depending on the deposition parameters. Data on structural transformations of the coatings under different tribological contact conditions were obtained, and secondary nucleation processes were investigated on different diamond faces during the deposition from the gas phase.

Polycrystalline diamond coatings have been grown on cemented carbide WC-6% Co substrates with different aspect ratios by microwave plasma CVD in CH4/H2 gas mixtures. Special plateholder with holes for group growth has been used to protect the edges of the substrates from non-uniform heating due to the plasma edge effect. The difference in heights Δh of the substrates and plateholder, and its influence on the diamond film mean grain size, growth rate, phase composition and stress was investigated. Diamond growth rate of 0.3–1 μm/h and compressive stress of 2.2–2.5 GPa, respectively were determined in the optimal Δh region. The substrate temperature range of 740–760 °C, within which uniform diamond films are produced with good adhesion, is determined. The diamond-coated samples produced at optimized process conditions exhibited a reduction of cutting force and wear resistance by a factor of two, and increase of cutting path length up to 8150 m or by 4.3 times upon turning А390 Al-Si alloy as compared to performance of uncoated tools.

A slow-neutron detector based on thin CVD diamond film is discussed. A deep graphitized layer in the diamond film acts as one of the electrodes in the detector. The detector demonstrates low sensitivity to γ radiation, at the background level. The detector is tested with a laboratory neutron source based on the isotope 252Cf in a moderator. Slow neutrons are detected by means of the boron isotope 10В and lithium isotope 6Li. In both cases, slow neutrons are recorded with about 3% efficiency. The efficiency of slow-neutron recording is also assessed theoretically.

New methods have been developed for obtaining three preceramic polycarbyne-family polymers. Poly(hydridocarbyne) (PHC) and poly(phenylcarbyne) (PPC) have been synthesized via a mechanically activated reaction between magnesium metal and CRX 3 (R = H, Ph; X = Br, Cl). Poly(naphthalene- co -hydridocarbyne) (PNHC) have been obtained by reacting CHBr 3 with sodium naphthalide. The efficiencies of PHC, PPC, and PNHC as sources of diamond nuclei in the microwave plasma chemical vapor deposition of diamond films on silicon substrates have been compared. The highest efficiency has been demonstrated by PHC with a high molecular weight, for which the nucleation density has been estimated at ≥ 10 9 nuclei per square centimeter of the substrate surface.

The paper deals on the response of a polycrystalline diamond sensor, 500 μm thick, to particles from a 90Sr β-source. 21 × 21 nano-carbon pads, with 0.18 mm × 0.18 mm area each, were realized by ArF excimer laser irradiation on one diamond face, whereas a 7 × 7 mm2 backside contact was fabricated and used for sensor biasing during characterization of sensor under β-source irradiation. The carbon pads embrace a number of grains, which show different degrees of surface graphitization dependent on the grain orientations. Each carbon pad exhibits a linear I(V) response up to 200 V. The average number of charge carriers collected by a single pixel, as well as the distribution of pixels involved by the impinging particle tracking, is analyzed as a function of the applied voltage recording the signals acquired by 16 pixels at a time. The pulse height distribution is not affected by reversing the bias polarity. For a single pixel, the most probable collected charge value is 1.40 ± 0.02 fC whereas the mean value gives 〈Q〉coll = 1.67 ± 0.02 fC (10,430 ± 120 electrons). The charge collection distance was measured taking into account the effect induced by high-energy electrons and found to be 285 ± 3 μm, demonstrating the absence of bulk defects induced by the laser graphitization processing. Cross-talk effects between nearest-neighbor pixels have been excluded analyzing the results obtained in a batch of more than 1000 events even if the same cannot be excluded under higher energy particles.

We used a low-coherence interferometry for precise continuous in situ measurements of thickness and growth rate of epitaxial single crystal diamond layers in microwave plasma CVD in H2-CH4 gas mixtures in a broad range of substrate temperatures Ts (750–1150 °C) and CH4 concentrations (1–13%). Rich growth kinetics is collected in a single experiment by depositing about 60 layers on one (100) Ib HPHT diamond substrate in different regimes (the substrate temperature was controlled by the microwave power) at fixed pressure P = 130 Torr, without the plasma switch-off. The growth rate is found to follow Arrhenius dependence with activation energy Ea = 11.1 ± 1.0 kcal/mol. By appropriate choice of the substrate temperature the growth rate can be significantly enhanced. The growth rate as high as 82 μm/h is achieved by optimizing the temperature and gas composition. At low CH4 content (1%) growth competes with etching by atomic hydrogen, the etching dominating at high Ts (> 1000 °C in the present conditions). The etching rate in pure H2 plasma was measured and activation energy Ea = 9.8 ± 0.8 kcal/mol was deduced. Gas temperature Tg in the plasma core evaluated from optical emission spectra for dimer C2 (Swan band), was found to be either constant or slightly and monotonically increasing with absorbed power, whereas the absorbed microwave power density shows a decreasing, although slight, trend. This suggests the temperature depended surface reactions to play a major role in the diamond growth kinetics under variable microwave power. Raman mapping of cross-section of the produced multilayered sample confirmed high quality of diamond structure over all the deposition regimes explored.

Nanocrystalline (NC) diamond films are grown by chemical vapor deposition on various single crystal diamond faces. Under conditions of NC diamond growth, the growing filmmorphology is reduced to two planes: {100} and {111}. The {100} planes are smooth and homoepitaxial layerby-layer growth occurs on them, whereas the NC film formed by twin crystalliteswith sizes of several tens and hundreds nanometers grows on {111} planes. Nitrogen impurity sharply increases the diamond growth rate.

A particle and ion detector based on an epitaxial layer of synthetic diamond is investigated. The p–i structure consists of a substrate comprised of HPHT p-type diamond, strongly doped with boron, on which ~10 μm thick, IIa-type, diamond CVD-film is deposited. Continuous contacts were deposited on the substrate and diamond CVD fi lm. The current-voltage characteristics of the p–i structure with deposited platinum contacts were measured. The detector was tested in fluxes of protons, deuterons, and α-particles obtained by means of an ion accelerator. The use of a diamond detector as a particle analyzer is promising in view of its unique properties, such as high radiation resistance and the possibility of operating at high temperature. The energy resolution of the detector and the minimum detectable particle energy were determined.

Comparative investigations of homoepitaxial diamond films with natural and modified isotopic compositions, grown by chemical vapor deposition (CVD) on type-Ib diamond substrates, are carried out using double-crystal X-ray diffractometry and topography. The lattice mismatch between the substrate and film is precisely measured. A decrease in the lattice constant on the order of (Δa/a)relax ∼ (1.1–1.2) × 10–4 is recorded in isotopically modified 13С (99.96%) films. The critical thicknesses of pseudomorphic diamond films is calculated. A significant increase in the dislocation density due to the elastic stress relaxation is revealed by X-ray topography.

Silicon-doped diamond nanopillars have been produced by a microwave plasma chemical vapor deposition (CVD) on a single crystal diamond substrate through holes in a Si mask perforated with a focused ion beam. Arrays of 400 nm diameter pillars with aspect ratio up to 2.8 are grown epitaxially being confined by channels in the mask, the latter serving also as the Si doping source. Strong photoluminescent (PL) emission of the SiV centers at 738.7 nm wavelength, localized within the pillars, has been detected and imaged with a fluorescence microscope. The SiV PL decay time of 1.1 ns has been deduced from PL kinetics measurements. An increase of specific PL intensity (intensity per unit volume of the pillar) with the aspect ratio is noted.

Isotopically pure 12С and 13С diamonds are synthesized by chemical vapor deposition and impulsive stimulated Raman scattering in these crystals is investigated. The thermal conductivity of 12С isotopically pure damond and natC diamond with natural isotopic composition is measured. Phonon-nondegenerate Stokes lasing based on the χ(3) nonlinearity in the 12С, 13С, and natC diamond “triad” is attained, which opens a new stage in the development of diamond photonics.

We performed synthesis of single crystal (SC) diamond by microwave plasma chemical vapor deposition in methane-enriched H2–CH4 gas mixtures, and achieved growth rates more than 30 μm/h, without adding nitrogen in reaction mixture. A low-coherence interferometry (LCI) was employed for precise measurements of the thickness and growth rate of the epitaxial diamond layers in the course of the process. The performance of this in situ technique is demonstrated by continuously monitoring the SC diamond thickness in a single growth run upon variation of CH4 percentage in steps, up to 17%, without switching off the plasma, to produce a “multilayer” diamond film. In addition, etching rate of diamond in pure hydrogen plasma has been evaluated with the same method. The LCI technique allows quick collection of growth kinetics data upon systematic variation of a selected process parameter for the growth optimization.

We report on fast polishing of polycrystalline CVD diamond films by ultrasonic machining in a slurry with diamond particles. The material removal mechanism is based on diamond micro-chipping by the bombarding diamond particles subjected to action of an ultrasonic radiator. The treated samples were characterized with optical profilometry, SEM, AFM and micro-Raman spectroscopy. The developed method demonstrates the polishing rate higher than those known for mechanical or thermo-mechanical polishing, particularly, the surface roughness of 0.5 mm thick film can be reduced in a static regime from initial value R a ≈ 5 μm to R a ≈ 0.5 μm for the processing time as short as 5 min. No appearance of amorphous carbon on the lapped surface was revealed, however, formation of defects in a sub-surface layer of a few microns thickness was deduced using Raman spectroscopy. The polishing of a moving workpiece confirmed the possibility to treat large-area diamond films.

Microwave (MW) plasma in silane-hydrogen and silane-hydrogen-methane mixtures is used effectively for chemical vapor deposition of Si, SiC, diamond, and SiC-diamond composite films; however, the properties of such plasma at pressures of the order of 100 Torr remain largely unexplored. Here we characterize the MW plasma (2.45 GHz) in SiH4 + H2 and SiH4 + СH4 + H2 mixtures (72 Torr) with silane content ranging from 0% to 5% in the process gas using high-resolution optical emission (OE) spectroscopy. Besides the OE lines of C2 dimer, Balmer series of excited atomic hydrogen (Hα, Hβ, Hγ, Hδ, and He), and CH radical, we observed atomic Si lines at 263, 288, and 391 nm and a relatively weak SiH emission. Gas temperature Tg of ≈3160 K is assessed from the rotational structure of the C2 dimer (Δν = 0, λ = 516.5 nm) emission band, and the absorbed microwave power density (MWPD) in the plasma fluctuates in the narrow range between 36 and 43 W/cm3 with a slight tendency to decrease with silane addition. The MWPD, intensity ratio Hα/Hβ of hydrogen Balmer series lines (related to excitation temperature Texc), and Si lines’ intensities in OE spectra as functions of SiH4 concentration in H2 and H2 + CH4 mixtures all show an extremum or a kink in slope near a special point at ≈0.5% SiH4. Finally, we produced a silicon carbide film of cubic polytype 3C-SiC on a (111) oriented Si substrate, which was characterized with Raman spectroscopy and x-ray diffraction, and its monocrystalline structure was confirmed.

Microwave plasma assisted chemical vapor deposition (MPCVD) is the established technique to produce high quality single crystal diamond (SCD). While typical pressures for SCD growth regimes in methane-hydrogen plasma are currently within 100–300 Torr, a transition to much high pressures promises enhanced growth rates. Here, we report on successful SCD synthesis by MPCVD in CH4-H2 gas mixtures at pressures up to 600 Tорр. A strong change of the plasma shape and volume (the latter shrinks by 10 times at fixed MW power) with pressure rise from 100 to 600 Torr was observed, still keeping the plasma stable. The record high absorbed MW power density of ≈1800 W/cm3 was achieved at 600 Torr. Optical emission spectroscopy (OES) was used for the plasma analysis via monitoring emission intensities of radicals Hα, C2 and CH. The gas temperature Tg determined from analysis of rotational fine structure of OES Swan transitions of dimer C2 (516 nm) turned out to be essentially constant ∼ 3100 ± 150 K over the pressure range explored. The diamond growth rate is found to increase by an order of magnitude with pressure to achieve 57 μm/h at 500 Torr at relatively low (4%) CH4 concentration, as measured in situ using low-coherence interferometry, but declined at further pressure increase. The produced films were characterized with SEM, XRD, Raman and photoluminescence spectroscopy, and a high/moderate quality of the obtained material was confirmed.

Microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) films were synthesized on Si substrates by a microwave plasma chemical vapor deposition in methane-hydrogen gas mixtures with a wide range of methane concentrations of 0.5–40%. The samples were investigated with scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. We observed an unusual transition of the produced material structure from MCD to NCD and again to MCD with the increase in CH4 content in the gas. The deposition rate, grain size, and the roughness of the films exhibited extrema in the middle of the methane concentration range ([CH4] = 20%). Further increase of CH4 percentage leads to improvement of the diamond film quality, as confirmed by Raman spectra and SEM images while keeping a high deposition rate. These results may be used for the growth of the wide range of PCD films to be used as multipurpose protective layers, hard coatings for the cutting tools, and the diamond base for composite MCD/NCD structures.

Thermal conductivity κ ( T ) of single crystal aluminum nitride grown by physical vapor transport has been measured at temperatures T from 5 to 410 K. The samples exhibit high thermal conductivity with a value of up to 316 W m − 1 K − 1 at room temperature and about 2800 W m − 1 K − 1 at a peak of 66 K. At lowest temperatures, κ ( T ) approaches the conductivity limited by the diffuse phonon scattering from sample surfaces. The peculiarities in measured κ ( T ) suggest that the phonon scattering from point defects contributes essentially to the total phonon scattering in samples under investigation at low temperatures. The phonon interaction with electrons and holes bound to neutral donor and acceptor centers is suggested, adding substantially to thermal resistivity near and below the peak in κ ( T ).

The article presents the results of using optical methods of non-destructive testing during synthesis of diamond coatings (DC) from microwave plasma (the MPCVD method) on hard alloy tools for processing highly abrasive composite materials. Using the methods of optical emission spectroscopy and measuring the operating temperature of the substrates applying an infrared pyrometer, the average discharge power density in a microwave plasma reactor during the group growth of micro- and nanocrystalline DC has been found for the first time. Heating control of cobalt-bonded hard alloy substrates in microwave plasma reactor is practically achieved by feedback with the indication of an infrared pyrometer. Using the Raman spectroscopy method, we confirm the result of applying a high-quality DC on a tool with thin cutting edges.The article presents the results of using optical methods of non-destructive testing during synthesis of diamond coatings (DC) from microwave plasma (the MPCVD method) on hard alloy tools for processing highly abrasive composite materials. Using the methods of optical emission spectroscopy and measuring the operating temperature of the substrates applying an infrared pyrometer, the average discharge power density in a microwave plasma reactor during the group growth of micro- and nanocrystalline DC has been found for the first time. Heating control of cobalt-bonded hard alloy substrates in microwave plasma reactor is practically achieved by feedback with the indication of an infrared pyrometer. Using the Raman spectroscopy method, we confirm the result of applying a high-quality DC on a tool with thin cutting edges.

We produced luminescent diamond films with embedded europium-contained fluorides which were synthesized by different precipitation techniques. Luminescence spectra showed a narrow orange line at 612 nm. This approach has a perspective for the preparation of luminescent diamond with wanted luminescence lines.

Thermal conductivity of three high purity synthetic single crystalline diamonds has been measured with high accuracy at temperatures from 6 to 410 K. The crystals grown by chemical vapor deposition and by high-pressure high-temperature technique demonstrate almost identical temperature dependencies $\ensuremath{\kappa}(T)$ and high values of thermal conductivity, up to 24 $\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ at room temperature. At conductivity maximum near 63 K, the magnitude of thermal conductivity reaches 285 $\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$, the highest value ever measured for diamonds with the natural carbon isotope composition. Experimental data were fitted with the classical Callaway model for the lattice thermal conductivity. A set of expressions for the anharmonic phonon scattering processes (normal and umklapp) has been proposed which gives an excellent fit to the experimental $\ensuremath{\kappa}(T)$ data over almost the whole temperature range explored. The model provides the strong isotope effect, nearly 45%, and the high thermal conductivity ($g24$ $\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$) for the defect-free diamond with the natural isotopic abundance at room temperature.

The response of high quality polycrystalline diamond pixel detectors to 90 Sr beta particles is reported. Laser induced surface graphitization was used to realize 36 conductive contacts with 1 mm×1 mm area each, pitch 1.2 mm, on one detector side whereas a 8 mm×8 mm large area graphite contact was realized on the other face for grounding or biasing. A proximity board was used to hold the matrix, the amplifiers and to bond nine pixels to test homogeneity of response among 36 detector pixels. Two configurations were used to test charge collection uniformity and signal dependence on voltage. Both configurations showed noise pedestal fitted with a Gaussian curve of 1150 equivalent electrons (1σ) and typical beta source particles spectrum. Reversing the bias polarity the pulse height distribution does not change and the saturation of most probable value of charge collection was observed around ±200 V (0.4 V/μm) with reasonable pixel response uniformity equal to a most probable value 1.28±0.05 fC. The charge collection efficiency (CCE) measurement was implemented using coincidence mode acquisition with an external trigger made by a commercial polycrystalline diamond slab. The detector shows a CCE=0.59 estimated using the 1 mm 2 large graphite pixel. The information earned with this first prototype will be used to design the new board with amplifying electronics for reading all 36 pixels at a time and perform experiments with monochromatic high energy electrons.

Doping of pristine materials can change their chemical and electrical properties. Namely nitrogen doping of graphene results in modulation of electronic properties of graphene. In this work we present experimental results on nitrogen doped graphene fabricated in two steps. At first, the graphene samples were synthesized by a chemical vapor deposition method on copper foils. Then they were treated with ammonia radio frequency discharge plasma. The prepared samples were investigated by atomic-force microscopy (AFM), scanning electron microscopy (SEM), Raman spectroscopy, optical absorption spectroscopy including Fourier transform infrared spectroscopy (FTIR), X-ray and ultraviolet photoelectron spectroscopy. In doped graphene a dependence of N-atom concentration on the treatment parameters has been revealed. A maximum doping level of 3 atomic % has been obtained and the shift of valence band maximum of 0.2 eV was observed at this concentration of nitrogen.