The results are presented for investigation of electrical conductivity of nanocrystalline diamond (NCD) films with thickness of 0.5-0.6 microns grown on silicon Si(100) substrates by the CVD method using methane-hydrogen and methane-hydrogen-oxygen mixtures. By the method of heating in vacuum with using hydrogen analyzer AB-1, the concentration of hydrogen in the studied films was determined and the relationship between the content of hydrogen in the NCD film and its conductivity was estimated. It has been shown that high-temperature processing in vacuum at the temperature of 600oC leads to desorption of hydrogen from the films and to a significant increase in their resistance. Keywords: nanocrystalline diamond, thin diamond films, electrical properties of films, hydrogen content.

Experimental temperature dependence of the resistiv- ity of thin (1−3 nm) highly boron-doped (close to the threshold of the phase transition into a state with a metallic-type conductivity) delta-layers in chemically vapor deposited (CVD) diamond in a broad temperature range from ∼ 100 to ∼ 500 K can be described by Mott’s two-dimensional law (hole ”hops“ between localized states with a temperature-dependent average ”hop“ length) in a low temperature region and Arrhenius’ law (hole ”hops“ between the nearest localized states) in a high temperature region. The crossover between them takes place at 230−300 K. The potentials of hole localized states are of a long-range, e. g. Coulomb’s, type, the static dielectric permittivities of delta-layers are by several times larger than those of undoped CVD diamond.

The results of a study of the incorporation of silicon in diamond depending on the growth conditions of epitaxial layers in a chemical vapor deposition (CVD) reactor in a gas mixture of hydrogen, methane, and silane are presented. A detailed study of the effect of methane and silane flows, substrate temperature, gas mixture pressure, and substrate misorientation angle has been carried out. The influence of the surface misorientation angle on the formation of silicon‐vacancy (SiV) centers in diamond has been studied. It has been found that the carbon content in the gas mixture has a significant effect on the incorporation of silicon into diamond. Studies of the CVD growth of silicon‐doped diamond are carried out simultaneously with studies of the optical spectra of plasma emission in the reactor. The content of silicon in plasma is compared with content of silicon incorporated into diamond during CVD synthesis. The most efficient formation of SiV centers is observed for substrate misorientation angles from 2° to 4°.

The report presents the results of a study of photo-cathodes based on phosphorus-doped nanocrystalline diamond films grown on conductive silicon substrates using the CVD method. The quantum efficiency of such cathodes was studied under the action of laser radiation with a wavelength of 266 nm and pulse duration of 15 ns. It has been found that the quantum efficiency increases with a decrease in the thickness of the diamond film, reaching a maximum at a thickness of 100 nm. In this case, the quantum efficiency was found to be 2.4 $\cdot 10^{-5}$ electrons per photon.

A new form of microwave discharge with a filament inside plasma volume was investigated in a microwave plasma-assisted chemical vapor deposition (CVD) reactor. The threshold values of methane content in a hydrogen-methane gas mixture, gas pressure, and microwave power for discharge transition to the new form were found. The parameters' range of existence of the new form of discharge was investigated in three types of CVD reactors. Measurements of the electron density, gas temperature, and spatial distributions of the plasma optical emission lines intensity were carried out for both forms of the discharge. The reasons for the transition of the discharge to a new form and the possibility of using the new discharge form in the microwave plasma-assisted (MPA) CVD reactor are discussed.

The study of the electroluminescence of silicon vacancy color centers (SiV centers) in the diamond p-i-n diode at high current density of 500 A/cm2 is presented. To create color centers, the internal region of the diode was doped with silicon. In the electroluminescence spectrum, the bright emission line at 738 nm corresponding to the SiV color center in a negative charge state was observed. Such bright emission is due to high current density. Additionally, the 946 nm line corresponding to the emission of the color center in a neutral charge state was observed in electroluminescence. Nanosecond voltage pulses were applied to study electroluminescence in a pulsed regime. Short emission pulses at 738 nm were demonstrated, showing the potential of creating electrically driven single photon source with “photon on demand” capability. By comparing the intensities of photoluminescence and electroluminescence, the possibility of obtaining single photon emission rate in a diode exceeding 106 photon/s is shown.

The results of a study of electroluminescence of silicon vacancy color centers (SiV centers) in a diamond merged diode with a structure involving parallel connection of a p–i–n diode and a Schottky diode are presented. To create color centers, the inner region of the diode is doped with silicon. In the luminescence spectrum, only a line at a wavelength of 738 nm is detected, corresponding to the emission of a SiV color center in a negative charge state. Emission at a wavelength of 946 nm, corresponding to the SiV color center in the neutral charge state, is not detected. The electroluminescence of color centers is observed only in the p–i–n region of the diode, that is, it is experimentally demonstrated that both types of charge carriers are necessary to excite electroluminescence. A pronounced dependence of the photoluminescence intensity of SiV centers on the applied voltage is found.

This work is devoted to experimental study of boron doped delta layers in CVD diamond. Delta layers with a thickness of 0.8 - 2 nm were grown with a concentration of boron atoms of (1 - 1.7)center dot 1021 cm-3, and localized inside undoped defect-free diamond. The layers thickness and boron concentration were mea-sured by secondary ion mass spectrometry (SIMS). The surface density and the Hall mobility of holes, the layer resistance at room temperature, and temperature dependences of these parameters are presented. Per-formed electrical measurements showed that, despite the perfect (from the point of view of the possibility of quantum effects) profile of delta layers, no significant increase was observed in the hole mobility compared to uniform doping with the same concentration of boron atoms. An explanation is proposed for the results of electrical measurements based on calculations of the delta layer profile and the concentration of delocalized holes depending on the layer thickness. It is discussed which parameters of the boron doped delta layers are needed in order to obtain a significant increase of the hole mobility in heavily doped diamond.

The results are presented for investigation of electrical conductivity of nanocrystalline diamond (NCD) films with thickness of 0.5-0.6 microns grown on silicon Si(100) substrate by CVD method using methane-hydrogen and methane-hydrogen-oxygen mixtures. By method of heating in vacuum with use of hydrogen analyzer AB-1 the concentration of hydrogen in the studied films was determined and the relationship between the content of hydrogen in the NCD film and its conductivity was estimated. It was shown that high-temperature processing in vacuum at temperature 6000 C leads to desorbtion of hydrogen from the films and a significant increase in their resistance.

This paper submits experimental results of a study directed towards the formation of Eu ions’ luminescent centers in CVD diamond films. A new approach is based on use of diamond nanoparticles with a surface modified with Eu ions for seeding at CVD growth. Nanocrystalline diamond films (NCD) doped with Eu have been grown from the gas phase on silicon substrates by microwave plasma-assisted CVD at a frequency of 2.45 GHz. The photoluminescence spectra clearly show several electronic transitions of the Eu3+ ions, which confirm the incorporation of Eu ions into the NCD film.

The creation of localized ensembles of nitrogen vacancy (NV) centers by nitrogen delta doping of chemical vapor deposition diamond with subsequent irradiation of the delta layer by an electron beam with electron energy of 200 keV and annealing at a temperature of 1200 °C is investigated. The concentration of created NV centers is determined as a function of the irradiation dose, and their spin properties are studied. The creation of 2D ensembles of NV centers with a surface density of ≈2500 μm−2 and spin coherence time T2 ≈ 33 μs is demonstrated.

A study of the process of diamond doping with silicon during CVD growth is presented. As a result, for the first time, a silicon-doped delta layer with a thickness of 5 nm and a depth localization accuracy of several nanometers was demonstrated.

This paper summarizes the results of studying the creation of localized ensembles of NV centers in a single-crystal diamond. The diamond was doped with nitrogen during its CVD growth. Due to the use of a microwave CVD reactor, in which a rapid (a few seconds) change in the composition of the gas mixture is realized, thin (nanometer thick) doped diamond layers were obtained, the position of which relative to the substrate surface is known with high accuracy. The possibility of forming a matrix of NV centers localized on the crystal surface is demonstrated. The results of studying the fluorescence of NV centers in such structures are presented.

Undoped nanocrystalline diamond (NCD) films less than 1 μm thick grown on Si (100) silicon by microwave plasma-assisted chemical vapor deposition at a frequency of 2.45 GHz are studied. To obtain diamond dielectric films with maximum resistivity the deposition of films in three gas mixtures is investigated: hydrogen-methane mixture, hydrogen-methane mixture with the addition of oxygen and hydrogen-methane mixture with the addition of an inert gas. A relationship has been established between the growth conditions, structural and electrical properties of NCD films. It is shown that for the use of NCD films as effective dielectrics preliminary high-temperature annealing of the films is required, for example, in vacuum at a temperature of 600°C for one hour.

Nitrogen-vacancy color centers in CVD diamond are promising candidates for many quantum applications. In particular, they can be used as sensors for electric and magnetic fields with high sensitivity and nanometer scale spatial resolution. When state readout is performed optically, only the NV− charge state can be used, therefore, it is important to have the maximum concentration of NV centers in the NV− state. In this work, the effect of combined nitrogen-phosphorus doping of diamond on the balance of charge states of NV centers is studied in a wide range of dopant concentrations and at different power of the laser used for photoluminescence excitation. It is shown that the use of a combination of doping with nitrogen and phosphorus makes it possible not only to ensure that NV centers in diamond predominantly exist in the NV− state, but also to stabilize the NV− state under conditions of high power of excitation laser. Cooling with liquid nitrogen allows to further increase the fraction of the NV− state. The obtained results may be applicable for a number of practical tasks, such as optimization of the sensitivity of magnetometers.

Undoped nanocrystalline diamond (NCD) films less than 1 μm thick grown on Si (100) silicon by microwave plasma-assisted chemical vapor deposition at a frequency of 2.45 GHz are studied. To obtain diamond dielectric films with maximum resistivity the deposition of films in three gas mixtures is investigated: hydrogen-methane mixture, hydrogen-methane mixture with the addition of oxygen and hydrogen-methane mixture with the addition of an inert gas. A relationship has been established between the growth conditions, structural and electrical properties of NCD films. It is shown that for the use of NCD films as effective dielectrics preliminary high-temperature annealing of the films is required, for example, in vacuum at a temperature of 600°C for one hour.

The effect of pulsed laser annealing on the formation of ohmic Mo/Ti contacts to diamond is studied. Using the method of secondary-ion mass spectrometry, it was shown that laser annealing of the contacts leads to effective diffusion of carbon atoms into the titanium layer and the formation of titanium carbide in the transition region with a diamond with a thickness of 15-20 nm. Rapid thermal annealing of the same contact system is accompanied by a sharp increase in the oxygen content in the titanium layer and in the transition layer with diamond and the formation of titanium oxide. In this case, the titanium carbide phase is not formed in the Ti-C transition layer. It was also shown that, in the used laser annealing mode, graphitization of the contact layer of diamond does not occur, which could drastically reduce the mechanical strength and adhesion of the contacts.

The possibility of controlled creation of NV centers at any given depth have a substantial potential for quantum information processing and sensor applications. Here we report on creation of localized NV centers using nitrogen delta doping during a chemical vapor deposition diamond growth process. Using confocal microscopy, we investigated optical properties of as grown NV centers in delta-doped layer, demonstrated availability of isolated space clusters of color centers in the layer, analyzed space distribution of these clusters, and using seconds-order correlation function measurements demonstrated that clusters contain from one to few color centers.

— The influence of pulsed laser annealing on the formation of ohmic molybdenum /titanium contacts to the diamond has been studied. Using the method of secondary ion mass spectrometry, it has been shown that the laser annealing of the contacts results in the effective diffusion of carbon atoms into the titanium layer and the formation of titanium carbide in the transition with a diamond region with a thickness of 15–20 nm. Rapid thermal annealing of the same contact system is accompanied by a sharp increase in the oxygen content in the titanium layer and the transition with a diamond layer and the appearance of titanium oxide. In this case, the titanium carbide phase is not formed in the titanium–carbon transition layer. It has been also shown that there is no graphitization of the diamond near-contact layer at the laser annealing mode used, which could have drastically reduced the mechanical strength and the adhesion of the contacts.

The results of a study of diamond p–i–n diode with a nitrogen‐doped intrinsic region on a substrate with the (001) orientation are presented. When the forward voltage is applied to the diode, a high current density of about 10 3 A cm −2 is obtained. Two narrow lines are detected in the electroluminescence spectrum of the p–i–n diode: one at a wavelength of 575 nm corresponding to the emission of the NV center (nitrogen‐vacancy color center) in a neutral charge state, and the second narrow line, which previously has not been observed in the electroluminescence spectra, at a wavelength of 533 nm. The line widths at room temperature are about 7 and 3 nm, respectively. By comparing the emission intensities of NV centers using the same optical registration system for electroluminescence and photoluminescence, the emission rate of NV centers during electroluminescence is estimated to be about 10 6 photon s −1 , which allows to consider a diode of such design as a possible candidate to create single‐photon sources.