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The paper considers the internal structure and electrical properties of conductive wires formed inside single crystal diamond by picosecond laser pulses under different processing conditions. Mechanically polished high-quality longitudinal sections of the wires were carefully examined using scanning electron microscopy, scanning spreading resistance microscopy, and Raman spectroscopy. It has been found that the interior of the wires consists of ~150-nm-thick sp2 sheets forming a conductive network inside the original diamond matrix. The sp2 sheets are clustered in segments distributed quasi-periodically along the wire. Both the velocity of the laser focus translation and the pulse energy have been found to influence the thickness of the sp2 sheets and spatial arrangement of the segments. The relationship between the internal structure of the wires and their integrated resistivity is discussed.

Laser beam tightly focused inside single-crystal diamond allows conducive microstructures to be fabricated via local phase transition of diamond to graphite. An extended modified region is formed in diamond due to propagation of so called laser-induced graphitization wave, which occurs immediately after the optical breakdown and propagates towards the laser beam even though the position of the laser focus is fixed. This paper is the first to consider the behavior of the graphitization wave when the laser focus uniformly moves towards the laser, which results in the formation of conductive wires of unlimited length in diamond. It has been found that there is an initial transitional period in the wire growth, during which velocities of the laser focus and the wire front are equalized owing to the change in the distance between them. After stabilization of the graphitization front velocity, the axial fluence at the front of the growing wire also reaches a constant value. It has been found that the stable laser fluence at the wire front is practically independent of the laser pulse energy, but it grows with increasing velocity of the laser focus. Such increase finally leads to violation of the physical criterion of the continuous wire growth, since the axial fluence at the wire front becomes higher than the diamond breakdown threshold. It has been shown that the minimal fluence providing propagation of the graphitization wave in diamond can be used to predict the lateral wire dimension.

The morphology, optical, spectroscopic and electrical characterization of mm-long graphite pillars created by picosecond pulsed laser irradiation (λ = 800 nm and 1 kHz of repetition rate), buried in single crystal CVD diamond to be employed as electrodes in a 3D diamond detector, is reported. The array of graphitized columns – 2.5 mm-long, with a diameter of ≈ 10 μm – consisted of two rows spaced by 110 μm with 12 pillars in each, which formed an interdigitated electrode structure embedded in the diamond crystal bulk. The presence of stressed regions along and between pillars were clearly shown with optical polarized microscopy, in a black field configuration. Confocal micro-Raman and photoluminescence analysis has been employed to scan local stresses, both generated around the graphitic wires and also developed on the pillars' plane. Defected/stressed regions with diameter of the order of 10 μm surrounding the individual pillars was measured, and paired carbon interstitials (3H defects) were also revealed. For the investigated structure, detrimental effects induced by such structural defects, clearly produced by laser-induced diamond-graphite transition, as well as the presence of a relatively high voltage drop along the graphitized pillars related to their own geometry have been reflected on the charge carriers collection performances evaluated under MeV β-particles. The creation of electronic active states within the diamond bandgap, as emphasized by spectral photoconductivity characterization, would play a fundamental role in lowering lifetime of generated carriers and then the detector collection efficiency. Indeed, states located in the middle of the diamond bandgap, acting as efficient recombination centers and decreasing the lifetime of generated carriers, drastically reduce the mean drift path of carriers and then the overall detector collection efficiency, as evaluated in the examined structure even at the highest applied voltages (up to 600 V).

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.

The effect of volatility of local electronic properties in multilayered (3–6 layers) graphene irradiated by nanosecond laser pulses with a wavelength 532 nm in humid atmosphere was found. The experiments were carried out in situ in a scanning probe microscope (SPM) with Pt/Si tip. It was established that along with local profile transformation of graphene sheet (the formation of "nanocrater" with depth up to 2 nm and ~1 µm diameter) in the zone of the laser action (~0,5 µm) a decrease (~20 meV) of the electrons work function was observed. It takes place in the region larger but comparable with the irradiation spot size. Analysis of the experimental data on local electrical conductivity have shown that the bottom of conduction band for graphene in laser irradiation area was reduced by ~ 50 meV. The observed changes of graphene physical properties were associated with the laser-induced radial displacement of the water layer intercalated between graphene and substrate. In addition, it was experimentally established that the graphene work function was decreased significantly less than can be expected for an "ideal" 3 - 6 layer graphene. The investigated process of laser-induced changes of graphene properties demonstrated the reproducible character and long-term stability. Possibility of laser fabrication of arrays in graphene with periodic modulation of electronic properties was demonstrated.

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.

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.

We report the manufacturing of a novel diamond – rare-earth (RE) composite material with EuF 3 nanoparticles (NP) embedded in the synthesized microcrystalline diamond films that show strong photoluminescence in the orange part of the visible spectrum. Synthesis of the aforementioned composite includes placement of EuF 3 NP on the diamond substrate and subsequent coating of them with an additional polycrystalline diamond layer grown by microwave plasma chemical vapor deposition (CVD). The produced composite films exhibit high intensity localized photoluminescence (PL) at 612 nm with the decay time of 0.34 ms, which is generated by the EuF 3 particles buried within a very stable transparent diamond matrix. The proposed synthetic approach is quite versatile, as it allows preparation of the luminescent diamond - RE particles nanocomposites of different sizes and natures which perform well over a broad range of the visible spectrum.

The focusing of hard x-rays was numerically simulated using a beam propagation method implemented in the BeamPROP software package and a Rayleigh-Sommerfeld integral. It was shown that when focusing hard X-rays of wavelength 1.34 A with sequentially arranged circular cylindrical microlenses (shaped as 10-µm micro-holes) found in a polycrystalline diamond film, a nearly 10 times shorter focal length of the microlens array can be achieved, reducing from 14.4 cm to 15 mm, via increasing the number of microlenses from 1 to 20. Meanwhile, the x-ray focal spot size was found to decrease 7 times along the minor axis from 1.5 μm to 200 nm, while the maximum intensity in the focus experienced a 40-times increase.

The role of the electric field during manipulations with diamond nanoparticles on a silicon substrate by a scanning probe microscope (SPM) tip is studied. It is found that the attractive force appearing in the contact between nanodiamond and an electrically charged tip is sufficient to detach and displace a chosen nanoparticle from initial to goal position under moderate mechanical stresses of the probe to nanoparticle. The problem of the control of the tip motion trajectory during manipulations is solved by visualizing the tip trace of the sample surface. The results obtained will be used for precision positioning of single-photon emitters based on luminescent nanodiamonds in microcavities.

The chemical etching of the surface of a natural diamond single crystal irradiated by subpicosecond laser pulses with a high repetition rate in air is experimentally investigated. The irradiation has been performed by the second-harmonic radiation of a disk Yb : YAG laser. Dependences of the diamond surface etch rate on the laser energy density and pulse repetition rate are obtained.

Scanning near-fi eld optical microscopy (SNOM) with an aperture probe has been used to map the luminescence of isolated submicron diamond crystallites. 532-nm laser light was used to excite luminescence of nitrogen-vacancy (NV) centers. The sizes of the analyzed diamond crystallites were determined with an atomic-force microscope. The optical resolution for the lateral dimensions of the luminescing diamond crystallites was doubled on going from confocal luminescence microscopy to scanning near-fi eld optical microscopy with a 290-nm probe aperture diameter.

In this paper we report on the study of the buried laser-modified region produced inside single crystal diamond by femtosecond laser irradiation. The cross-section of the modified region was prepared via precise mechanical polishing to investigate its intrinsic structure with Raman spectroscopy, scanning electron microscopy and scanning spreading resistance microscopy. It is found that the opaque laser-modified region is pierced by 40–100 nm thick sheets of graphenic carbon united into a single conductive network, while the gaps between the sheets are filled by diamond. Only small part of the irradiated diamond volume (∼16 vol. %) is transformed into the sp 2 phase. The results obtained are consistent with the model of laser-induced crack-assisted phase transition in diamond bulk proposed earlier.

Silicon-doped microcrystalline diamond films of 1 μm thickness were grown by chemical vapor deposition in microwave plasma from mixtures of methane–hydrogen–silane on substrates of aluminum nitride, tungsten, and silicon. The diamond films were found to contain optically active silicon vacancy (SiV) centers giving rise to the 737-nm band in the photoluminescence spectra. The spectral features of a newly discovered narrow band of comparable intensity at 720–722 nm were studied. It is shown that the band at 720–722 nm occurs in the photoluminescence spectra only in the presence of silica in the diamond, regardless of the substrate material. The temperature dynamics of the photoluminescence spectra in the range of 5–294 K were investigated. The possible nature and mechanisms of formation of the color centers responsible for the 720–722 nm band are discussed.

Comparison of the two laser sources (UV nanosecond and IR femtosecond) used for the formation of micro-relief at the silicon surface showed the advantage of the second one. A four-level silicon diffractive THz Fresnel lens has been fabricated by laser ablation at high repetition rate (f = 200 kHz) of femtosecond Yb:YAG laser. Features of the lens were investigated in the beam of the Novosibirsk free electron laser at the wavelength of 141 μm. Detailed results of investigation of fabricated lens micro-relief are presented. The measured diffractive efficiency of the lens is in good agreement with the theoretical prediction.

Surface modification of conductive boron-doped diamond has been conducted using the electrical field of the probe of a scanning probe microscope (SPM) at varying relative humidity (RH) of the ambient environment. It has been found that, under the action of positive polarity pulses applied to the sample via a grounded SPM probe, the sample material undergoes modification. The modification pattern depends on atmospheric RH: low (up to 32%) and high humidity values (above 35%) lead to the formation of cavities and protrusions, respectively. It has been found that the resulting protrusions exhibit temporary instability; that is, a protrusion is partially transformed into an array of nanoobjects. The mechanism of modification of boron-doped diamond–local anodic oxidation–has been discussed.

We have investigated the role of adsorption water in the local transformation of multilayer graphene deposited on an oxidised silicon substrate, which was exposed to nanosecond low-intensity focused laser radiation with a wavelength of 532 nm in the air. Experimental data obtained for a laser energy density E = 0.04 J cm-2 suggest that the formation of micropits (craters) is a consequence of the multipulse removal of the layer of a water adsorbate, which is intercalated between graphene and the substrate, from the zone of laser irradiation of the graphene sheet. The energy threshold of graphene damage in the regions devoid of water was found to be higher in comparison with the initial one (0.058 against 0.048 J cm-2). According to computer simulations of the heating dynamics of the sample and the heat distribution in the substrate – adsorbate – graphene multilayer system, at energy densities corresponding to the experimental ones the water adsorbate layer heats to a temperature sufficiently high to form an increased-pressure vapour cavity under the graphene film.

Graphitized structures are fabricated on the polycrystalline diamond surface using an excimer KrF (λ = 248 nm, τ = 20 ns) and a Ti:Al2O3 (λ = 400 nm, τ = 120 fs) lasers. It is shown that the conductivity of formed structures is independent of the energy density and the number of pulses per surface point in the case of the excimer laser, whereas such a dependence was observed for femtosecond pulses. The causes of the dependence of the conductivity of surface structures on laser irradiation parameters are discussed.

Matrix evaporation caused by heat accumulation between scans (HAS) was studied in the case of multi-pass scanning of a laser beam over the surface of carbon fiber reinforced plastic (CFRP). The experiments were performed in two regimes, namely, in the process of CFRP cutting and in the regime of low-fluence irradiation avoiding ablation of carbon fibers. The feature of the ablation-free regime is that all absorbed energy remains in the material as heat, while in the cutting regime the fraction of residual heat is unknown. An analytical model based on two-dimensional (2D) heat flow was applied to predict the critical number of scans, after which the HAS effect causes a distinct growth of the matrix evaporation zone (MEZ). According to the model, the critical number of scans decreases exponentially with increasing laser power, while no dependence on the feed rate is expected. It was found that the model fits well to the experimental data obtained in the ablation-free regime where the heat input is well defined and known. In the cutting regime the measured significant reduction of the critical number of scans observed in deep grooves may be attributed to transformation of the heat flow geometry and to an expected increase of the residual heat fraction.

The paper reports the study of an asymmetric detector with graphite contacts, about 20 µ m in diameter, buried within a synthetic single crystal diamond. To induce diamond-to-graphite transformation a femtosecond IR laser is used on the surface and bulk volume. Optical microscopy with crossed polarizers has evidenced optical anisotropy laterally the buried pillared contacts whereas the regions between pillars exhibited the presence of both tensile and compressive stress there around, as revealed with Raman spectroscopy mapping. Notwithstanding the strain, the buried electrodes showed linear electrical response and demonstrated ability to collect the charge carriers produced by 3.0 and 4.5 MeV protons as well as MeV electrons emitted by 90Sr. The charge collection efficiency (CCE) dependence on voltage evaluated using 4.5 MeV protons in the ±100 V range saturates at around 92±2% at 100 V, while coincidence experiments with MeV electrons confirmed that the whole pillars length is active in collecting the charge carriers. The mapping of CCE spatial distribution with an ion beam induced current technique showed that only a narrow (a few microns) damaged zone around the graphite electrodes has a reduced CCE, while the main diamond volume preserves excellent detection properties.

The morphology, optical, spectroscopic and electrical characterization of mm-long graphite pillars created by picosecond pulsed laser irradiation ( λ = 800 nm and 1 kHz of repetition rate), buried in single crystal CVD diamond to be employed as electrodes in a 3D diamond detector, is reported. The array of graphitized columns – 2.5 mm-long, with a diameter of ≈ 10 µ m – consisted of two rows spaced by 110 µ m with 12 pillars in each, which formed an interdigitated electrode structure embedded in the diamond crystal bulk. The presence of stressed regions along and between pillars were clearly shown with optical polarized microscopy, in a black field configuration. Confocal micro-Raman and photoluminescence analysis has been employed to scan local stresses, both generated around the graphitic wires and also developed on the pillars’ plane. Defected / stressed regions with diameter of the order of 10 µ m surrounding the individual pillars was measured, and paired carbon interstitials (3H defects) were also revealed. For the investigated structure, detrimental e ff ects induced by such structural defects, clearly produced by laser-induced diamond-graphite transition, as well as the presence of a relatively high voltage drop along the graphitized pillars related to their own geometry have been reflected on the charge carriers collection performances evaluated under MeV β-particles. The creation of electronic active states within the diamond bandgap, as emphasized by spectral photoconductivity characterization, would play a fundamental role in lowering lifetime of generated carriers and then the detector collection e ffi ciency. Indeed, states located in the middle of the diamond bandgap, acting as e ffi cient recombination centers and decreasing the lifetime of generated carriers, drastically reduce the mean drift path of barriers and then the overall detector collection e ffi ciency, as evaluated in the examined structure even at the highest applied voltages (up to 600 V).

The possibility of fabricating a silicon diffractive fourlevel THz Fresnel lens by laser ablation is studied. For a microrelief to be formed on the sample surface, use is made of a femtosecond Yb : YAG laser with a high pulse repetition rate (f = 200 kHz). Characteristics of the diffractive optical element are investigated in the beam of a 141-mm free-electron laser. The measured diffraction efficiency of the lens is in good agreement with the theoretical estimate.

Nanocrystalline diamond (NCD) and microcrystalline diamond (MCD) films with bright photoluminescence (PL) of silicon-vacancy (SiV) color centers at 738 nm have been grown using a microwave plasma CVD technique. The films were doped with Si via adding silane to CH4–H2 reaction gas mixture in the course of the deposition process. The dependence of SiV PL intensity on silane concentration in gas shows a maximum at SiH4/CH4 ratios of 0.2% and 0.6% for NCD and MCD films, respectively, the maximum intensity for MCD being an order of magnitude stronger compared with that for NCD. The PL quenching at higher CH4 addition occurs, however, no significant degradation of the film structure, such as Si-induced amorphous carbon formation, was observed within the SiH4 concentration range studied (0%–0.9%). The higher PL efficiency of the MCD films is related to their less defective structure, as deduced from Raman spectroscopy analysis.

Multi-layered graphene deposited on silicon wafer was irradiated in air by sequences of nanosecond laser pulses. It is shown that ultra-shallow craters (cavities) with depth of ~1 nm and microholes can be formed in graphene sheet on the substrate at laser fluence ~0.04 J/cm 2 well below the experimentally known graphene ablation threshold ≥0.25 J/cm 2 . Influence of intensity and number of laser pulses on the depth and roughness of the cavities are described. We suggest that the observed effects are related to laser heating and boiling of the adsorbate at graphene-silicon interface.

In germanium-doped thin polycrystalline diamond films grown in microwave plasma on Ge substrates, strong photoluminescence in the orange spectral region with a zero-phonon line (ZPL) at a wavelength of 602 nm is detected. The ZPL width is 4–5 nm at room temperature and 1.2 nm at T = 5K. It is assumed that the new optically active defect is a germanium–vacancy (Ge–V) complex similar to the known Si–V color center in diamond.

We have studied the upper limits for incorporation of nitrogen and formation of arrays of nitrogen–vacancy (NV) color centers in optical-quality single-crystalline diamond synthesized by chemical vapor deposition (CVD). The CVD diamond samples were grown in a microwave plasma in methane–hydrogen mixtures with high content (200–2000 ppm) of the nitrogen dopant in the gas mixture, and were analyzed using Raman and photoluminescence spectroscopy. From the UV absorption spectra, we established that the solubility limit for substitutional nitrogen in the studied material is close to 2·1018 cm–3 (under typical synthesis conditions), which lets us in particular form arrays of NV center with similar concentrations by means of irradiation and annealing.

Multi-pulse laser irradiation of diamond bulk after the optical breakdown causes extension of continuous graphitized region toward the laser beam that can be described as propagation of a “graphitization wave.” Velocity of the graphitization wave in single-crystal diamond is measured experimentally as a function of local laser fluence for a few numerical apertures (NA = 0.36–0.09), pulsewidths (140 fs–5 ps), and beam orientations (along [110] or [100] diamond axes). The experimental results are used to develop the model of the crack-assisted thermal graphitization of diamond at the boundary of the laser-modified region. Velocity of the graphitization wave is determined in general case by diffusion of heat from the light-absorbing modified region. The revealed rise in the graphitization wave velocity for the [110] beam orientation can be explained by the local electric field enhancement near the crack tip, which facilitates diamond ionization and plasma-assisted energy absorption. The proposed model predicts a specific internal structure of the laser-modified region: the network of graphitic inclusions with diamond-filled gaps between them.

The method of epitaxial growth of localized photoluminescence sources in the form of the ordered microcolumn diamond structures with silicon-vacancy (SiV) color centers is implemented. The process is based on diamond deposition in microwave plasma in CH4-H2 mixtures in microwells in a silicon mask on a diamond single crystal substrate, where the Si mask itself is a silicon doping source. Strong photoluminescence of SiV centers at a wavelength of 738 nm is detected; the spatial distribution of luminescence completely coincides with the synthesized structure arrangement.

Results of an experimental-theoretical study of spallation in synthetic diamonds are presented. In this study, data were first obtained on dynamic tensile strength of poly- and singlecrystal diamond samples at mechanical loads of up to 0.34 TPa and strain rates of 10–100 µs−1. Shock-wave loading was performed by 70 ps laser pulses on a Kamerton-T facility using a Nd:glass laser (second harmonics λ = 527 nm, pulse energy of up to ≈3 J) at intensities of ≈8 TW/cm2. The obtained maximal value of the spall strength ≈16.4 GPa is 24% of the theoretical ultimate strength of diamond. Raman scattering experiments showed that a small amount of diamond was graphitized in the spall area on the backside of the sample.

The processes of the synthesis of silicon-doped microcrystalline diamond films on AlN and Si substrates in microwave plasma in “methane-hydrogen-silane” mixtures were studied. It is shown that the dependence of the photoluminescence (PL) line intensity of silicon-vacancy centers in diamond (λ = 738 nm) on the silane concentration in a gas mixture passes through a maximum at SiH4/CH4 concentrations of 0.1% for Si substrates and 0.6% SiH4/CH4 for aluminum nitride substrates. It was found that such nonmonotonic variation of the PL intensity with increasing silane concentration occurs despite the unchanged growth rate of the diamond film, its structure, and phase composition in the studied silane concentration SiH4/CH4 range of 0–0.9%.

Aleksandr Mikhailovich Prokhorov was a Russian physicist, academician, one of the originators of quantum electronics, laser physics and laser technologies, winner of the 1964 Nobel Prize in Physics 'for fundamental work in the field of quantum electronics, which has led to the construction of oscillators and amplifiers based on the maser – laser principle' (shared with N.G. Basov and Ch.H. Townes), Lenin Prize and State Prize winner and twice Hero of Socialist Labour.

The excitation of an electronic subsystem of an yttrium aluminum garnet by 800 nm femtosecond radiation was studied theoretically and experimentally. The spatio-temporal dynamics of the refractive index (n) inside the beam waist was explored by means of the pump–probe interferometric technique with a submicron resolution. The observed increase in n indicated the formation of bound electronic states relaxed for $${\sim}150$$ ps. We showed that the experimental data agreed with the computational simulation based on the numerical solution of the nonlinear Schrodinger equation only if these transient states were considered to arise from a direct light-induced process but not from the decay of radiatively generated free-electron–hole pairs.

Arrays of diamond photoemitters with silicon-vacancy (SiV) photoluminescent (PL) centers have been produced by epitaxy of CVD diamond inside laser-ablated channels in a-Si mask on single crystal or polycrystalline diamond substrates, the mask also serving as Si-doping source. Strong PL emission from the SiV centers with zero-phonon line at 738.6 nm wavelength (6 nm width, 0.8 ns decay time), localized within the photoemitters, has been measured.

Hardness of single-crystal CVD diamond placed into a shell of a diamond composite thermostable material produced at high pressures and temperatures as well as structural variations in diamond during indentation have been studied.

Results of the experimental investigation of the spallation phenomenon in polycrystalline and single-crystal synthetic diamond are presented. The shock-wave action on the target was formed by a laser pulse with a duration of 70 ps using a Kamerton-T installation. To attain the ablation pressure of 0.66 TPa on the face surface of the target, the laser radiation of the Nd:glass laser (second harmonics λ = 527 nm, the pulse energy is 2.5 J) was used at intensity up to 2 × 1013 W/cm2. The attained maximal spall strength of diamond σ* ∼ 16.5 GPa is 24% of the theoretical ultimate strength. The Raman scattering indicates that a small amount of crystalline diamond is graphitized in the spall region on the back target side.

The spallation phenomena in poly- and single-crystal synthetic diamonds have been experimentally investigated. A shockwave impact on a target was implemented using a 70-ps laser pulse in the Kamerton-T facility. The ablation pressure of 0.66 TPa on the front target surface was formed by pulsed radiation of a neodymium phosphate glass laser (second harmonic λ = 0.527 mm, pulse energy 2.5 J) with an intensity as high as 2 × 1013 W cm-2. The maximum diamond spall strength σ* ≈ 16.5 GPa is found to be 24% of the theoretical ultimate strength. Raman scattering data indicate that a small amount of crystalline diamond in the spallation region on the rear side of the target is graphitised.

Properties of impact diamonds from the Popigai Deposit have been studied in a free state and in a composition of a compact. Raman spectra have been taken of the initial micron powders and polycrystals HP-HT sintered both in the presence of sintering aids and without them. Hardness, H V , of sintered polycrystals have been found, structural variations in diamond crystal lattice depending on the sintering conditions have been studied.

The effect of mechanical polishing on the surface topography of mono-and polycrystalline diamond films produced by microwave plasma deposition and synthetic diamond crystals is investigated. The values of the temperature and friction coefficient of diamond films during polishing on the cast iron disk are measured. After finishing treatment, the surface roughness of a single crystal diamond is ∼0.5 nm and that of a polycrystal one is ∼8.1 nm. Because of the difference in wear rate of misoriented crystallites in the diamond film, nanosteps are formed on the grain boundaries.

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.