Abstract This work reports on defect engineering related to optical centers in diamond by ion implantation. In particular, we demonstrate that thermal diffusion of vacancies to a few micrometers in ...depth can be effectively suppressed provided these are electrically charged and located within the depletion region of an abrupt p + -n junction. The observed effect is complementary to the observations in the previous study (Favaro et al 2017 Nat. Commun. 8 15409) showing that charging of implantation-induced vacancies at such junction structures in diamond inhibits the formation of vacancy complexes in proximity to the targeted optical centers. In the present work we first generate vacancies near the surface of a low nitrogen doped CVD diamond substrate by He and C ion implantation before these are diffused by annealing at 1200 ∘ C into the bulk. In the next step the depth distribution of NV centers generated by trapping of these vacancies is analyzed on a micron scale. For precise tuning of the implantation conditions we derived data on the boron and nitrogen doping by step etching of planar p + resistors and p + -n- p + diode structures combined with electrical characterization and modeling. In the next step, tin-vacancy (SnV) centers were produced by 40 keV Sn implantation across the same junction structures at optimized conditions. In this way we observe an enhancement of the SnV yield and noticeable suppression of NV centers by diffusion and trapping of vacancies along the tracks of tin ions. Such ‘subsidiary’ NVs could significantly affect the emission of SnV and potentially other centers in the same spectral range.
Abstract
Advances in applications of nitrogen-vacancy (NV) spin centers in diamond for sensing and quantum metrology depend critically on the NV fabrication methods. One such technique combines ...epitaxial diamond growth and electron or ion irradiation (He, C, etc.), where NVs are activated by vacancy trapping at the nitrogen donor atoms upon thermal diffusion. In this work we study the efficiency of such method by analyzing NV depth profiles created by 340keV and also 4keV He irradiation in high purity CVD and HPHT diamond crystals and subjected to sequent annealing at 950◦C and 1200◦C temperatures. This analysis is coupled with the measurement of NV density in the bulk of CVD diamonds with nitrogen doping at low-ppb and low-ppm levels, exposed to MeV electrons in a wide range of the doses. For data analysis we developed an atomistic model based on probabilistic atomic jumps in a crystal lattice, which considers competitive trapping between di-(V
2
) or multi-vacancy defects compared to that of NVs. The efficiency of NV formation was defined as a ratio of the corresponding capture cross sections: σ
NV
vs. σ
V
2
. Applying this model to the experimental data, the σ
NV
/ σ
V
2
ratio was estimated about 0.1-to-0.5, where the activation energy of vacancy diffusion of about 1.7 eV was evaluated by 3-D localization of individual NVsin depth profiles in a confocal microscope and sampling their spin coherence properties (T
2
). In addition, we noted two subsidiary effects also discussed here: (i) reduction of NV density within the stopping range of the implanted He atoms after 1200◦ annealing and, (ii) partial suppression of NVs at near-surface areas visible only at low-dose electron exposures. The results of this study could be helpful to optimize the NV fabrication process reducing the density of “collateral” lattice damage.
The ability to optically initialize the electronic spin of the nitrogen-vacancy (NV) center in diamond has long been considered a valuable resource to enhance the polarization of neighboring nuclei, ...but efficient polarization transfer to spin species outside the diamond crystal has proven challenging. Here we demonstrate variable-magnetic-field, microwave-enabled cross-polarization from the NV electronic spin to protons in a model viscous fluid in contact with the diamond surface. Further, slight changes in the cross-relaxation rate as a function of the wait time between successive repetitions of the transfer protocol suggest slower molecular dynamics near the diamond surface compared to that in bulk. This observation is consistent with present models of the microscopic structure of a fluid and can be exploited to estimate the diffusion coefficient near a solid–liquid interface, of importance in colloid science.
The creation of modern CNC machines requires the development of the design of machine feed drives with specified performance criteria. Ensuring the characteristics of feed drives that meet these ...criteria is largely related to the reasonable choice of design and technological parameters of standing connections available in the design. It is shown that this task, due to the presence of several conflicting criteria and a significant number of variable design parameters (VDP), is the task of parametric multi-criteria synthesis of compounds. The stages of the procedure of parametric multi-criteria synthesis of stationary machine tools are considered. The design variables and the formation of permissible regions of their variation, determined by the presence of parametric, functional, and criterion constraints, are analyzed in detail. It is indicated that the determination of the solution search area (the Pareto region) is most conveniently performed by scanning using the LPτ -sequence. It is proposed, in connection with the complexity of describing the boundaries of the Pareto region, to use its approximation by the described hyper-parallelepiped. Since the area of the search for solutions is characterized by the fact that any solution belonging to it cannot be improved simultaneously by all criteria, it is proposed to use a generalized criterion, calculated during scanning, when selecting possible deviations of the VDP from nominal values. Calculations performed according to the proposed procedure for the left support of the running screw of the longitudinal feed drive of the CNC machine mod. 1P426DF3, allowed to determine the nominal values and deviations of each of the VDP standing connections.
The nature of the neutrino is one of the major open questions in experimental nuclear and particle physics. The most sensitive known method to establish the Majorana nature of the neutrino is ...detection of the ultra-rare process of neutrinoless double beta decay. However, identification of one or a handful of decay events within a large mass of candidate isotope, without obfuscation by backgrounds is a formidable experimental challenge. One hypothetical method for achieving ultra- low-background neutrinoless double beta decay sensitivity is the detection of single
Ba ions produced in the decay of
Xe ("barium tagging"). To implement such a method, a single-ion-sensitive barium detector must be developed and demonstrated in bulk liquid or dry gaseous xenon. This paper reports on the development of two families of dry-phase barium chemosensor molecules for use in high pressure xenon gas detectors, synthesized specifically for this purpose. One particularly promising candidate, an anthracene substituted aza-18-crown-6 ether, is shown to respond in the dry phase with almost no intrinsic background from the unchelated state, and to be amenable to barium sensing through fluorescence microscopy. This interdisciplinary advance, paired with earlier work demonstrating sensitivity to single barium ions in solution, opens a new path toward single ion detection in high pressure xenon gas.
The results of the analysis of the influence of various design parameters on the dynamics of the spindle knot of the machine-tool are presented. As a dynamic characteristic, the natural frequencies ...were chosen. When choosing a dynamic model, the features of spindle knots were taken into account, which do not allow to take full advantage of the rich experience accumulated for rotary systems. The first feature is that modern spindles are massive shafts with areas that are insignificantly different in diameter. This makes it possible to neglect gyroscopic forces when considering the spindle dynamics. The second feature is the asymmetric location of the center of mass relative to the supports. Another feature of the spindle knots is the need to provide high rigidity of the spindle unit in the processing area, whereupon the radial stiffness of the front support is usually several times higher than the rigidity of the back support. Based on a single-mass dynamic model with two degrees of freedom, which performs translational-angular oscillations, the influence of design parameters on the values of natural frequencies was analyzed. As the design parameters, the mass and the moment of inertia of the spindle, the rigidity of the supports, the inter-bearing distance, the position of the center of mass (mass distribution over the front and back supports) were chosen. It was found that the anisotropy of the elastic properties of the spindle supports creates a band of natural frequencies. This complicates the monitoring task, since it requires taking into account the orientation of the hodographs of rigidity and a clear fixation of the direction of control of the oscillations of the spindle. In order to increase the spindle's natural frequencies, an increase in the stiffnesses of the front and back supports, an increase in the distance determining the position of the back support relative to the center of mass, a reduction in the mass of the spindle and the moment of inertia can be envisaged during the design. It is noted that the fastening of the workpiece in the chuck of the machine-tool practically does not affect the values of the natural frequencies. The results of the analysis allow at the design stage to select rational design solutions for the projected machine, create a system for ensuring the predicted dynamic characteristics and organize monitoring of the technical condition of the equipment by a dynamic criterion.
The structural elucidation of primary and secondary peroxidation products, formed from complex lipids, is a challenge in lipid analysis. In the present study, rare minor oxidized cerebrosides, ...isolated from the extract of a far eastern deep-sea glass sponge,
sp., were analyzed as constituents of a multi-component RP-HPLC (high-performance liquid chromatography on reversed-phase column) fraction using NMR (nuclear magnetic resonance) spectroscopy, mass spectrometry, GC (gas chromatography), and chemical transformations (including hydrogenation or derivatization with dimethyl disulfide before hydrolysis). Eighteen previously unknown β-D-glucopyranosyl-(1→1)-ceramides (
-
,
-
,
-
,
-
,
-
,
-
) were shown to contain phytosphingosine-type backbones (2
,3
,4
,11
)-2-aminoeicos-11-ene-1,3,4-triol (in
), (2
,3
,4
,13
)-2-aminoeicos-13-ene-1,3,4-triol (in
), and (13
*,14
*)-2-amino-13,14-methylene-eicosane-1,3,4-triol (in
). These backbones were
-acylated with straight-chain monoenoic (2
)-2-hydroxy acids that had allylic hydroperoxy/hydroxy/keto groups on C-17
in the 15
-23:1 chain (
-
), C-16
in the 17
-23:1 (
-
) and 14
-22:1 (
-
) chains, and C-15
in the 16
-22:1 chain (
-
). Utilizing complementary instrumental and chemical methods allowed for the first detailed structural analysis of a complex mixture of glycosphingolipids, containing allylically oxygenated monoenoic acyl chains.
We report the experimental studies of radiation on fundamental and third cyclotron harmonic from a Ka-band high-current relativistic gyrotron with a maximum output power of 40 MW. Helical electron ...beam is formed by the electron optics system based on using the kicker field for initiation of electrons' gyration and its subsequent pitching in increasing magnetic field. Based on the spectral measurements, we estimate indirectly the radiation power level at the third harmonic of the gyro-frequency as about −30 dB with respect to the first-harmonic radiation level. This estimation is in good agreement with the results of 3-D particle-in-cell (PIC) simulations.
The processing on CNC machines of parts of a complex profile with multipass shaping schemes is accompanied by multiple changes in the direction of movement of the working bodies (reverse) during the ...cutting process and at idle running. When reverse, loss of information is possible due to the presence of gaps in the chain of feed drive and elastic deformations determined by constant loads overcome by the drive. Permanent loads consist of cutting forces and friction in the feed drive chain. Information loss is defined as a position insensitive zone at a position. To determine the insensitive zone, a technique is proposed that takes into account the differential accounting of friction losses in the mechanical feed drive chain. To estimate the elastic deformations in the drive chain, design schemes are proposed and analytical dependencies obtained. Differentiated consideration of friction in determining the insensitive zone allows you to outline the main ways to improve feed drives. It is shown that the magnitude of the preload on the thrust bearings and the tensile forces of the lead screw during assembly do not have a significant effect on the size of the insensitive zone. Even less impact on the dead zone has a preload change in the transfer screw-nut rolling. It was determined that the main ways to reduce the insensitivity zone is to increase the rigidity of the screw-and-nut rolling transmission anchor to the machine carriage and reduce friction in the guides. In addition, an analysis of the layout decisions of the lead screw assembly (one-sided and two-sided termination) according to the insensitive zone criterion showed that the use of one-sided termination of the lead screw is more rational.
Silver is the most famous bactericidal element known from ancient times. Its antibacterial and antifungal effects are typically associated with the Ag ionization and concentration of Ag+ ions in a ...bacterial culture. Herein we thoroughly studied the influence of surface topography and roughness on the rate of Ag+ ion release. We considered two types of biocompatible and bioactive TiCaPCON-Ag films with 1 and 2 at. % of Ag and nine types of Ti surfaces with an average roughness varying in the range from 5.4 × 10–2 to 12.6 μm and different topographic features obtained through polishing, sandblasting, laser treatment, and pulsed electrospark deposition. It is demonstrated that the Ag+ ion release rates do not depend on the Ag content in the films as the main parameter, and it is other factors, such as the state of Ag agglomeration, surface topography and roughness, as well as kinetics of surface oxidation, that play a critical role. The obtained results clearly show a synergistic effect of the Ag content in the film and surface topography and roughness on Ag+ ion release. By changing the surface topographical features at a constant content of bactericidal element, we showed that the Ag+ ion release can be either accelerated by 2.5 times or almost completely suppressed. Despite low Ag+ ion concentration in physiological solution (<40 ppb), samples with specially fabricated surface reliefs (flakes or holes) showed a pronounced antibacterial effect already after 3 h of immersion in E. coli bacterial culture. Thus, our results open up new possibilities for the production of cost-effective, scalable, and biologically safe implants with pronounced antibacterial characteristics for future applications in the orthopedic field.
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