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Density functional theory was employed to examine the adsorption and thermal evolution of nitrogen species on diamond(111) impacted by microwave N2 plasma. On bare domains of diamond, as represented by the models of C(111)-2 × 1 and graphite-like C(111), N2(ad) is identified as the major surface species; the desorption of N2(ad) proceeds on both models via a concerted process of breaking two C–N bonds. By contrast, there is evidence of the formation of (NH)2(ad) via the insertion reaction of microwave N2 plasma on hydrogenated domains of diamond, as represented by the models of C(111)-2 × 1-H and C(111)-1 × 1-H. Interestingly, contrasting dynamics of desorption of (NH)2(ad) are presented on these two models, that is, via sequential breaking of two C–N bonds on C(111)-2 × 1-H and via concerted breaking of both C–N bonds on C(111)-1 × 1-H. Our results demonstrate that the observed diversity of surface nitrogen species in composition, bonding, vibration, and desorption in prior experiments is linked to domains of a variety of surface terminations and reconstructions on diamond(111). [ABSTRACT FROM AUTHOR]

The authors implanted P atoms at 50 and 140-keV energies with respective fluences of 1 × 10 14 and 2 × 10 14 /cm 2 into diamond thin films synthesized by chemical vapor deposition on the type-Ib diamond substrate formed by high-pressure and high-temperature conditions. The occupational sites of implanted P atoms were determined in each processing stage of P implantation, ion-beam-induced epitaxial crystallization (IBIEC) annealing by 3-MeV-Ne 2 + ion irradiation at 750 ° C, and thermal annealing at 850 ° C in vacuum, by quantitatively comparing the random and channeling yields in Rutherford backscattering (RBS) measurements. In the analysis of RBS spectra, simulated distributions were fitted to the experimentally obtained spectra and we quantitatively identified the occupational sites and ratio of implanted P atoms. In addition, we investigated the diffusion phenomenon of implanted P atoms during annealing processes from the depth profile of scattered He ions. Consequently, the averaged occupational ratio in the substitutional lattice site was stably recorded around 50%. From the depth profile in the RBS spectra, thermal diffusion of implanted P atoms was clearly observed during the last thermal annealing after MeV-IBIEC annealing. We finally discuss the potentials of the MeV-IBIEC irradiation at relatively low temperatures applying to useful and credible annealing methods for electrical activation as well as recovery of damaged crystallinity. [ABSTRACT FROM AUTHOR]

In this work, nitrogen vacancy (NV) centers of high nitrogen diamond implanted with arsenic ions were investigated by photoluminescence spectroscopy. The transition of the NV center charge state was discussed by the regularly changing laser excitation power and measurement temperature following high-temperature annealing. After high-temperature annealing, the amorphous layer generated by arsenic ion implantation is transformed into a graphitization layer, resulting in a decrease in the NV yield. The electric neutral NV (NV0) center and negatively charged NV (NV−) center are affected by both radiation recombination and Auger recombination with increasing laser power. Accompanied by the increasing measurement temperature, the intensities of NV centers gradually decreased and eventually quenched. In addition, the charge states of NV− and NV0 centers were undergoing a transition. The zero phonon line positions of NV centers were also red shift, it was attributed to the dominant role of electron–phonon interaction in the temperature-dependent displacement of diamond energy gaps. The full width at half maxima of NV center were broadened significantly at higher temperatures. [ABSTRACT FROM AUTHOR]

Due to fascinating physical properties powered by remarkable progress in chemical vapor deposition of high-quality epilayers, diamond thin films attract great attention for fabrication of nitrogen-vacancy-based solid-state spin systems capable of operating in ambient conditions. To date, diamond heteroepitaxy via bias-enhanced nucleation is an unavoidable method for reliable wafer-scale film manufacturing. In this work, we analyze the coalescence phenomena in nitrogen doped, heteroepitaxial diamond epilayers, with a particular focus on their specific role in the annihilation of macroscopic crystal irregularities such as grain boundaries, non-oriented grains, and twinned segments. Here, we also report on the growth mechanism for the "primary" crystal orientation along with a predominant formation of two different types of boundaries highlighting the {011}-type as a main source of the crystal lattice irregularities. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate a hydrogen-terminated diamond (H-diamond) field-effect transistor (FET) with Al2O3/CeB6 gate materials. The CeB6 and Al2O3 films have been deposited by electron beam evaporation technique, sequentially. For the 4/8/12/15 μm gate length (LG) devices, the whole devices demonstrate distinct p-type normally off characteristics, and all the threshold voltage are negative; all the absolute values of leakage current density are 10−4 A/cm2 at a VGS of −11 V, exhibiting a relatively low leakage current density compared with CeB6 FETs, and this further demonstrates the feasibility of the introduction of Al2O3 to reduce the leakage current density; the maximum drain–source current density is −114.6, −96.0, −80.9, and −73.7 mA/mm, which may be benefited from the well-protected channel. For the 12 μm LG devices, the saturation carrier mobility is 593.6 cm2/V s, demonstrating a good channel transport characteristic. This work may provide a promising strategy for the application of normally off H-diamond FETs significantly. [ABSTRACT FROM AUTHOR]

Mn-doped diamond (111) layers were grown by microwave plasma chemical vapor deposition using bis(methylcyclopentadienyl)manganese as a Mn source. The Mn concentration ([Mn]) was intentionally controlled in the range between ∼1 × 1015 and ∼1 × 1017 cm−3 by regulating the Mn/C molar ratio in the gas phase within 0.15%–3.0%. When [Mn] > ∼1 × 1016 cm−3, the step edges of the growing surface changed from straight to a zigzag shape. Using a model based on the classic theory by Cabrera and Vermilyea, we show that this roughening of the step edges resulted from step pinning due to Mn atoms absorbed on the diamond surfaces. [ABSTRACT FROM AUTHOR]

We deduce equations to calculate coupling coefficients of diamond micro-ring resonators. The equations can be used universally at any wavelength but not limited to the transmission peaks/valleys, and can be adapted with triangular cross-sections and tapered waveguides. Consequently, we build three models in accordance to different diamond processing technologies. These models deal with ring resonators with either rectangular cross sections, or triangular cross sections, or with tapered bus for triangular cross sections. The calculated coupling coefficients can be well fitted by exponential decay functions of gap d. Due to geometrical limitations, triangular-cross-sectional diamond resonators are shown to have much smaller (factor 20) coupling coefficients than those of rectangular-cross-sectional resonators. A tapered bus is shown to be beneficial to increase the coupling coefficient. Besides the calculation of coupling coefficients, the method presented in the paper can also be used to calculate the bending loss of micro-ring resonators, as a complement to the existing methods. [ABSTRACT FROM AUTHOR]

This paper reports the energies and charge and spin distributions of the low-lying excited states in singlet and triplet N2V defects in diamond from direct Δ-SCF calculations based on Gaussian orbitals within the B3LYP, PBE0, and HSE06 functionals. They assign the observed absorption at 2.463 eV, first reported by Davies et al. [Proc. R. Soc. London 351, 245 (1976)], to the excitation of a N(sp3) lone-pair electron in the singlet and triplet states, respectively, with estimates of ∼1.1 eV for that of the unpaired electrons, C(sp3). In both cases, the excited states are predicted to be highly local and strongly excitonic with 81% of the C(sp3) and 87% of the N(sp3) excited charges localized at the three C atoms nearest neighbor (nn) to the excitation sites. Also reported are the higher excited gap states of both the N lone pair and C unpaired electron. Calculated excitation energies of the bonding sp3 hybrids of the C atoms nn to the four inner atoms are close to that of the bulk, which indicates that the N2V defect is largely a local defect. The present results are in broad agreement with those reported by Udvarhelyi et al. [Phys. Rev. B 96, 155211 (2017)] from plane wave HSE06 calculations, notably for the N lone pair excitation energy, for which both predict an energy of ∼2.7 eV but with a difference of ∼0.5 eV for the excitation of the unpaired electron. [ABSTRACT FROM AUTHOR]

Masers—the microwave analog of lasers—are coherent microwave sources that can act as oscillators or quantum-limited amplifiers. Masers have historically required high vacuum and cryogenic temperatures to operate, but recently, masers based on diamond have been demonstrated to operate at room temperature and pressure, opening a route to new applications as ultra-low noise microwave amplifiers. For these new applications to become feasible at a mass scale, it is important to optimize diamond masers by minimizing their size and maximizing the power of signals that can be amplified. Here, we develop and numerically solve an extended rate equation model to present a detailed phenomenology of masing dynamics and determine the optimal properties required for the copper cavity, dielectric resonator, and gain medium in order to develop portable maser devices. We conclude by suggesting how the material parameters of the diamond gain media and dielectric resonators used in diamond masers can be optimized, and how rate equation models could be further developed to incorporate the effects of temperature and nitrogen concentration on spin lifetimes. [ABSTRACT FROM AUTHOR]

Three sets of heteroepitaxial diamond crystals grown under nominally identical process conditions on Ir/YSZ/Si(001) substrates have been studied with respect to structural defects, chemical purity, and x-ray induced photoconductivity (PC). The dislocation density that varied systematically between 10 7 and 10 9 cm − 2 had a minor influence on dark conductivity and photoconductive gain G. In contrast, the substitutional nitrogen (N N ) and substitutional boron (N B ) defects, which are both present at very low concentrations (≤ 1 ppb), turned out to be the crucial factors controlling the electrical behavior. Small differences between both resulted in variations of the photocurrents by up to 5 orders of magnitude. The maximum in G of 0.75 × 10 4 was measured in the sample with highest dark conductivity. It could be explained conclusively within our model calculations on gain formation by N N ≤ N B . For low gain samples, we found N N > --> N B . However, the measured G values were far from theoretical predictions. This indicates a dominating role of additional traps. After x-ray switch-off, persistent photoconductivity (PPC) was observed in high gain samples. It was attributed to an energetic barrier hampering the recharging of nitrogen atoms by hole capture. As a possible source, strain fields generated by dislocations are suggested. [ABSTRACT FROM AUTHOR]

Detailed characterization of deep-level color centers requires understanding their electronic and atomic structure, which is most commonly investigated utilizing the Kohn–Sham density functional theory. Standard semilocal functionals based on the generalized gradient approximation (GGA) are inclined toward an imprecise quantitative description of defects' electronic structure. Hybrid functionals provide an improved prediction of electronic properties, albeit at a much higher computational cost. In this work, we test the newly developed Strongly Constrained and Appropriately Normed (SCAN) family of meta-GGA density functionals for selected color centers in diamond. In particular, we study nitrogen-, silicon-, germanium-, and tin-vacancy centers that have been recently investigated for their use in quantum technological applications. We show that SCAN and its derivatives, the rSCAN and r2SCAN functionals, significantly improve the calculated energies of optical transitions within the delta-self-consistent-field approach, almost reaching the accuracy of the hybrid Heyd–Scuseria–Ernzerhof (HSE) functional. In the case of the NV− center, we also show that the SCAN family of functionals improves the description of the adiabatic potential energy surfaces compared to both GGA and hybrid functionals, improving calculated luminescence lineshapes. As a result of these findings, we recommend using the SCAN family of functionals as a promising alternative for studying color centers in solids. [ABSTRACT FROM AUTHOR]

The advent of the new 5G communication standard has introduced demanding requirements for the performance of RF front-end filters, necessitating high frequency, large bandwidth, and other improved parameters. Consequently, researchers have been actively investigating the potential of surface acoustic wave resonators and film bulk acoustic resonators to address these needs, leading to the development of numerous novel structures. Through finite element simulation, a new heterogeneous stack structure Al/LN/diamond/Si with an interdigitated electrode resonant cavity is proposed. And the advantageous role of a diamond thin film in the surface acoustic wave resonant structure, including the excitation of high-frequency acoustic resonance modes and modulation of the electromechanical coupling coefficient has been studied. This structure holds promise for addressing the increasing demands for high-frequency, large-bandwidth RF front-end filters in the context of the new 5G communication standard. The results show that the central resonant frequency of the new structure resonator is 5284 MHz, the electromechanical coupling coefficient is 10.96%, and the Q factor value is 10 316, which has potential application value in the field of high-frequency filtering. [ABSTRACT FROM AUTHOR]

The properties of bulk contribution to sum-frequency generation reflected and transmitted by a finite layer in a multilayer system are described. The leading term is essentially due to the processes emitting in the transmission geometry, in particular for macroscopic layers. For such transmission processes, phase mismatch leads to the production of interference fringes when the layer thickness or a wavelength is tuned, which may be mistaken for resonant processes inside or at the surface of the material. Experimental evidence of such fringes measured from centrosymmetric bulks is provided for a diamond window in the far infrared and suggested for other materials in previously published data. The existence of a stationary point in the phase mismatch, related to the group velocity mismatch, is shown to be the source of another pseudo-resonant process in centrosymmetric calcium and barium fluorides, for which theoretical predictions reproduce the experimental observations. [ABSTRACT FROM AUTHOR]

For the wafer-scale fabrication of diamond devices, the growth of diamond substrates by heteroepitaxial chemical vapor deposition is the most promising option currently available. However, the transfer of growth and also structuring processes from small homoepitaxial to larger heteroepitaxial samples is not straightforward and requires adaptation. In this study, we present an approach for the fabrication of functional microstructures including pyramids and mesas as well as more complex structures with hollow centers. The associated methods were previously demonstrated by homoepitaxial growth and are now evaluated on heteroepitaxially grown diamond films. After optimizing the growth procedures to ensure a sufficient quality of the bare diamond substrates, precursor structures for overgrowth were fabricated by e-beam lithography and plasma etching. In the overgrowth of nanopillars, a truncated pyramidal shape was achieved. The characterization with scanning electron microscopy revealed the growth of higher-index facets. Nevertheless, photoluminescence spectroscopy reveals localized doping on the sides of the microstructures. In addition, optically detected magnetic resonance reaches a contrast of 6 % of one preferred nitrogen vacancy orientation per facet and a transverse relaxation time T 2 ∗ of 96 ns. [ABSTRACT FROM AUTHOR]

Control of the charge state of the nitrogen-vacancy (NV) center is crucial because of its instability and its transitions between the negative (NV–) and neutral (NV0) NV charge states under laser irradiation In this study, we fabricated an n-i-n junction, with an i-layer sandwiched between two phosphorus-doped n-layers; then, we measured the charge state of NV centers under steady state and laser irradiation in a known band structure where the Fermi energy changes gradually. The steady-state charge state measured by a nondestructive single shot exhibited stable NV– and NV0 signals when the Fermi level was even slightly above and below the transition level, respectively. This result indicates that the charge state can be significantly stabilized through band engineering. Both charge-state populations were observed only when the Fermi level was close to the transition level. Under continuous green laser irradiation, the ratio of NV– measured by the photoluminescence spectra changed gradually with the Fermi level in the depletion layer because of the balance between excitation from the laser and the supply of charge from the band. This outcome agrees reasonably with the calculated bands. Furthermore, we measured the PL spectra of the ensemble NV centers and discovered that their charge state can be well-controlled, as in the single NV center. The charge state of the i-layer at the interface can be stabilized by depositing a thin n-layer on the surface. These results would contribute significantly to improve sensor performance. [ABSTRACT FROM AUTHOR]

Quantum diamond magnetometers using lock-in detection have successfully detected weak bio-magnetic fields from neurons, a live mammalian muscle, and a live mouse heart. This opens up the possibility of quantum diamond magnetometers visualizing microscopic distributions of the bio-magnetic fields. Here, we demonstrate a lock-in-based widefield quantum diamond microscopy, achieving a mean volume-normalized per-pixel sensitivity of 43.9 nT μ m 1.5 / H z 0.5 . We optimize the sensitivity by implementing a double resonance with hyperfine driving and magnetic field alignment along the ⟨ 001 ⟩ orientation of the diamond. Additionally, we show that sub-ms temporal resolution (∼ 0.4 ms) can be achieved while keeping the per-pixel sensitivity at a few tens of nanotesla per second using quantum diamond microscopy. This lock-in-based diamond quantum microscopy could be a step forward in mapping functional activity in neuronal networks in micrometer spatial resolution. [ABSTRACT FROM AUTHOR]

Controllability of nitrogen doping, types of nitrogen-related defects, and their charge states in homoepitaxial diamond (001) crystals were investigated. For these purposes, 15N-doped 12C-enriched free-standing chemical vapor deposited diamond (001) crystals were grown through long-time growth using 12C-enriched methane as the carbon source gas and 15N-enriched molecular nitrogen as the nitrogen source gas. The formation of non-epitaxial crystallites and growth hillocks was suppressed by the application of the oxygen-adding growth condition. Nitrogen was incorporated uniformly into the crystals, with a concentration variation of less than 10%. About 70% of the total nitrogen was substitutional nitrogen in a neutral charge state Ns0. Hydrogen was incorporated at approximately the same concentration as nitrogen. Both NV and NVH centers were predominantly negatively charged defect structures, i.e., NV− and NHV− centers. The concentrations of NHV− centers were less than 5% of the total nitrogen concentration. Nitrogen concentration in diamond crystals was controlled by changing the N/C gas ratio over a wide doping range from 10 ppb to 10 ppm. Nitrogen incorporation efficiency was found to be (1.5 ± 0.5) × 10−4 in this study. [ABSTRACT FROM AUTHOR]

Nucleation is important in processing of good quality diamond crystals and textured thin films by microwave plasma enhanced chemical vapor deposition (MPECVD) for applications in quantum devices and systems. Bias-enhanced nucleation (BEN) is one approach for diamond nucleation in situ during MPECVD. However, the mechanism of diamond nucleation by BEN is not well understood. This paper describes results on the nucleation of diamond within a carbon film upon application of electric field during the BEN-facilitated MPECVD process. The nature of the diamond film and nuclei formed is characterized by SEM (scanning electron microscopy), Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM). The HRTEM images and associated diffraction patterns of the nucleation layer show that the diamond nuclei are formed within the carbon film close to the Si (100) substrate surface under the influence of microwaves and electric fields that lead to formation of the textured diamond film and crystal upon further growth. These results are expected to develop diamond films of optimum quality containing a nitrogen-vacancy center for application in quantum systems. [ABSTRACT FROM AUTHOR]

A series of high-pressure multi-anvil experiments were conducted in the MgO-Al 2 O 3 system between 15 and 50 GPa and at temperatures up to 2623 K, to determine the solubility of Al 2 O 3 in periclase in the stability fields of coexisting spinel, corundum, the Mg 2 Al 2 O 5 modified ludwigite phase, the MgAl 2 O 4 calcium ferrite phase, and the MgAl 2 O 4 calcium titanate phase. The Al 2 O 3 solubility in periclase is strongly temperature-dependent over the conditions investigated. Conversely, periclase Al 2 O 3 solubility exhibits a negative relationship with pressure. Experiments with up to 40 mol.% FeO in ferropericlase show Al 2 O 3 solubilities that are near identical to those of periclase, within experimental uncertainties. A simple thermodynamic model incorporating significant literature on ambient pressure measurements is able to describe periclase Al 2 O 3 solubility up to 40 GPa. This model is used to investigate the Al 2 O 3 contents of ferropericlase inclusions observed in natural diamonds, which vary up to 0.35 mol. %. Pressure–temperature curves along which particular inclusions formed can be produced if equilibrium can be assumed with Al-bearing minerals found in the same diamond. Alternatively, the maximum possible Al 2 O 3 content in ferropericlase can be determined for a certain pressure–temperature profile and inclusions with Al 2 O 3 contents that exceed this curve can be excluded from those conditions. To obtain such solubility curves, calculations are performed for periclase coexisting with the Al-rich phases spinel, garnet, bridgmanite and the MgAl 2 O 4 calcium ferrite phase. The calculations indicate that periclase, and by inference ferropericlase, Al 2 O 3 -contents cannot be greater than 0.5 mol.% under present day adiabatic mantle temperatures and go through a minimum at mantle transition zone conditions. This excludes a number of Al-rich ferropericlase inclusions found in natural diamonds from being formed in the transition zone, unless temperatures were super-adiabatic. This subset of inclusions likely formed either at the base of the upper mantle or the top of the lower mantle, but must have formed at near adiabatic temperatures. The majority of ferropericlase inclusions have Al 2 O 3 contents that would be consistent with formation in the transition zone at near slab temperatures, but could still have been formed at higher temperatures if Al 2 O 3 activities were low. [ABSTRACT FROM AUTHOR]

Boron‐doped diamond is a wide‐bandgap semiconductor with excellent semiconductor properties, which is widely utilized in various applications. Till now, the thermodynamic rules governing the carrier transitions in this material have not been fully understood. In this research, the different luminescence behaviors of boron‐doped diamond under 193 nm pulse laser with high‐ and low‐ power density excitation are analyzed. Under high‐power density excitation (@≈63 kW cm−2), the emission intensity of excitons is nearly ten times higher than that of defect luminescence. Conversely, under low‐power density excitation (@≈1.4 kW cm−2, different emission peaks exhibit similar intensities, indicating a competitive relationship among them. Based on experimental and theoretical analyses, the difference is attributed to the thermodynamic distribution of carriers at varying excitation powers. Specifically, high excitation power brings an independent behavior of each emission peak, and the exciton emission is described by a phonon‐assisted radiation model; different from that, the competition among different emission centers under the condition of low excitation power cannot be neglected, and now the thermodynamic evolution of each emission peak is described by a carrier trapping‐dissociation model. [ABSTRACT FROM AUTHOR]

Diamond Schottky barrier diodes (SBDs) could theoretically operate at high voltage, high temperature, and high frequency and be potentially used in power electronics. However, the device breaks down prematurely and cannot operate stably at high voltages due to the edge electric field crowding. In this work, a vertical diamond SBD with a curved field plate (CFP) was prepared using a chemical reflow method, inductively coupled plasma etching, and electron-beam evaporation. This structure alleviates the electric field crowding at the edge of the Schottky electrode and results in a breakdown voltage and current density of 380 V and over 3000 A/cm2, respectively. After repetitive measurements, we found that the device can repeatedly breakdown at around 380 V. These results indicate that CFP structure diamond SBDs have great application in high-voltage and high-power electronic devices. [ABSTRACT FROM AUTHOR]

Excessive use of azithromycin (AZM) is associated with resistance and negative impacts on the environment. Therefore, this study aimed to develop an electrochemical sensor for AZM. The screen‐printed carbon electrode (SPCE) modified with boron‐doped diamond nanoparticle (BDDNP) and reduced‐graphene oxide (rGO) was successfully applied to measure the AZM concentration. The morphology of the modified electrode was characterized by scanning electron microscopy‐energy dispersive X‐ray (SEM‐EDX). Furthermore, the effect of electrochemical parameters, such as signal per background, scan rate, and selectivity was determined. The results showed that under optimum conditions, the plot of AZM demonstrated linearity in the range of 30–100 μM with a limit of detection (LOD) at 1.6 μM. The repeatability and recovery were also investigated, and the sensor was applied to real samples obtained from hospital wastewater. A remarkable 93.27 % recovery rate and excellent precision were recorded with an %RSD of 2.41 %. This study underscores the potential of SPCE modified with rGO/BDDNP for accurate and reliable measurement of AZM levels, showcasing great applicability in addressing the challenges associated with monitoring AZM in various environmental settings. [ABSTRACT FROM AUTHOR]

The phase relations of Al-bearing magnetite were investigated between 6–22 GPa and 1000–1550 °C using a multi-anvil apparatus. This study demonstrates that the spinel-structured phase persists up to ~9–10 GPa at 1100–1400 °C irrespective of the amount of hercynite (FeAl2O4) component present (20, 40, or 60 mol%). At ~10 GPa, the assemblage Fe2(Al,Fe)2O5 + (Al,Fe)2O3 forms and remains stable up to 16–20 GPa and 1200–1550 °C. Fe2(Al,Fe)2O5 adopts the CaFe3O5-type structure with the Cmcm space group. At 18–22 GPa and T > 1300 °C the assemblage Fe3(Fe,Al)4O9 + (Al,Fe)2O3 becomes stable. Fe3(Fe,Al)4O9 is isostructural with Fe7O9, having the monoclinic structure of the C2/m space group. At T <1300 °C, Fe3(Fe,Al)4O9 + (Al,Fe)2O3 gives way to the assemblage of a hp-Fe(Fe,Al)2O4 + (Al,Fe)2O3. This hp-Fe(Fe,Al)2O4 phase is unquenchable; a defect-bearing spinel-structured phase was recovered instead, and it contained numerous lamellae parallel to {100} or {113} planes and notably less Al than the initial starting composition. While low-pressure spinel can have a complete solid solution between Fe3+-Al, the post-spinel phases have only very limited Al solubility, with a maximum of ~0.1 cpfu Al in hp-Fe(Fe,Al)2O4, ~0.3 cpfu in Fe2(Fe,Al)2O5, and ~0.4 cpfu in Fe3(Fe,Al)4O9, respectively. As a result, the phase relations of Fe(Fe0.8Al0.2)2O4 can also be applied to bulk compositions richer in Al with the only difference being that larger amounts of an (Al,Fe)2O3 phase are present. Coexisting rhombohedral-structured phases demonstrate that the binary miscibility gap established at low pressure between hematite and corundum is still valid up to 20 GPa. Since iron oxides (e.g., magnetite) with variable Al contents are found in extraterrestrial rocks or as inclusions in diamond, constraints on their high-P-T-fO2 stability might help unravel their formation conditions. [ABSTRACT FROM AUTHOR]

There is an extensive range of carbon substances with poorly ordered structures that are not well understood. Yet they are important indicators of conditions of related geological processes. The carbon minerals include nanocrystalline graphite, natural analogs of glass-like carbon (GLC)—shungite and impact ultrahigh-pressure GLC, recently discovered ultranocrystalline diamond, as well as natural carbon nanocomposites of diamond, lonsdaleite, and graphite. Studying these natural carbon substances using a standard Raman approach with excitation by visible radiation may lead to a significant distortion of the understanding of their phase states. This paper presents in detail for the first time the spectral features of natural, poorly ordered, and multiphase sp2-sp3 carbon composites by multi-wave Raman spectroscopy using laser excitations from visible to ultraviolet light applied to natural low-ordered carbon substances—nanocrystalline graphite and shungite, nanocrystalline and ultranocrystalline diamond, and multiphase carbon aggregates. The carbon state resolution advantages of ultraviolet Raman spectroscopy for phase analysis of nanostructured and poorly ordered polycomponent carbon substances containing sp2- and sp3-carbons are presented. Raman spectroscopy with ultraviolet excitation can also be applied in the analysis of industrial carbon materials, such as glassy carbon and functional carbon nanocomposites, including ultranocrystalline diamond, lonsdaleite, and amorphous sp3-carbon components. [ABSTRACT FROM AUTHOR]

Reaction-bonded boron carbide composites were fabricated by molten silicon infiltration of diamond-containing boron carbide preforms. The effects of diamond particle size on the microstructure, mechanical and tribological properties of reaction-bonded boron carbide composites were investigated. Fine diamond particles (≤7.7 µm) completely reacted with silicon generating nano silicon carbide particles, which bonded the boron carbide particles forming a 3-D ceramic skeleton and improving the flexural strength of the composites. Coarser diamond (≥24 µm) particles were retained protected by a dense SiC layer generated from the reaction of diamond and molten silicon. A "core-shell" structure with the retained diamond as the "core" and with the reaction formed silicon carbide as the "shell" formed. Relief structures were established on the composites' surface during the wear process, greatly reducing the friction coefficient and improving the wear resistance. [ABSTRACT FROM AUTHOR]

For high dielectric constant, conductive carbide ceramic fillers are scattered in polymer to fabricate composites. However, high conductivity of carbides will lead to high leakage conductance and dielectric loss. In this work, to balance dielectric properties, polymer/ZrC/diamond blends were prepared via complementation of fillers. To perform property comparison, polymer/ZrC blends were prepared. Crystal forms and micromorphology of fillers were confirmed. All blends were measured to obtain dielectric constant, dielectric loss and conductivity at various frequencies. Compared to polymer/ZrC blends, dielectric constant of ternary blends slightly decreases and dielectric loss sharply reduces. By analysing ternary blends, strong interaction at polymer/ZrC interface results in high dielectric constant and insulating diamond results in low-dielectric loss via greatly-decreased leakage conductance. Partner employment of ZrC and diamond is distinctive. Ternary blend loaded with 5 wt% ZrC and 3 wt% diamond exhibits well-balanced dielectric performances (dielectric constant ~ 35.3; dielectric loss ~ 0.48) at 100 Hz. This work will provide valid route for balancing dielectric properties of polymer/conductive carbide blends. [ABSTRACT FROM AUTHOR]

Polycrystalline diamond compacts (PDC) with three different substrate geometries and trimodal diamond particle formulation were fabricated. The properties of prepared PDC including Vickers hardness, toughness, wear performance, and thermal stability were evaluated. The microscopic features including morphology, elemental and phase composition, and residual stress state were systematically investigated. The optimal substrate contributing to best comprehensive properties of PDC was singled out. Discrepancies in the properties of PDCs with different substrate geometries were mainly in fracture toughness and impact toughness, with maximum and minimum values of 6.54 MPa m1/2/3120 J and 5 MPa m1/2/1680 J, respectively. The best wear performance was 5.88 mm2/60P. The results showed that the tendency of wear performance was consistent with toughness and thermal stability, showing a strong correlation. The substrate geometry affected the morphology and composition of the cobalt transition layer in the interface, which had a significant impact on its toughness. Differences in residual stress states induced by the interfacial geometries were also important determining PDC's impact toughness. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC)-bonded diamond materials, comprising approximately 50% diamond by volume, represent innovative composites with exceptional mechanical and thermal properties, including high hardness, wear and corrosion resistance, and elevated thermal conductivity. Despite these advantageous properties, the machining of these composites presents formidable challenges due to their extremely high hardness. Grinding with diamond tools is commonly employed among the limited viable machining methods. However, the efficiency of this process is hindered by high grinding forces, elevated temperatures, and significantly high tool wear. Additionally, the surface integrity, form, and dimensional accuracy of the workpiece are compromised by the effects of tool wear and high cutting forces. To address these technological constraints in the grinding of SiC-bonded diamond materials, a laser-assisted grinding process has been developed. Ultra-short pulsed laser radiations were effectively utilized to induce material ablation with controlled structural damages, enhancing the productivity and efficiency of the grinding process through reduced grinding forces, temperatures, and tool wear. Furthermore, this study investigated the influence of grinding tools' specifications, design variations, and parameters on key aspects such as grinding forces, surface quality, and tool wear. Substantial reductions of up to 70% in tangential grinding forces, 83% in normal grinding forces, and a modest improvement in surface roughness achieved. The surface integrity analysis revealed a damage-free ground surface when utilizing laser assistance. Furthermore, there was a substantial enhancement in the grinding ratio (G-ratio), achieving an increase of up to 247%, concurrently with a noteworthy improvement in the actual removal depth, reaching up to 99%, when compared to conventional grinding processes. Compared to the utilized segmented metal bonded diamond grinding wheel, the vitrified bonded diamond grinding wheel induced lower grinding forces and higher actual removal rates. [ABSTRACT FROM AUTHOR]

In this contribution, we are interested in the prediction of the macroscopic thermal conductivity of three-phasic composite materials such as wood fibers. The main idea is to make use of up-scaling such as homogenization to link the pore scale and the sample scale. The studied wood species incorporates three phases: the air, the lumen or matrix and the fibers. Image processing is preformed on a tomographic acquisition with high resolution of some micrometers. It serves to identify the present phases and generates the morphology mesh. The 2D diamond scheme is employed to discretize Fourier's model posed on the segmented morphology. The resulting algorithm is validated using an exact solution. Optimal numerical convergence rates of second order are recorded. The thermal conductivity is therefore estimated following the 2D orthotropic directions. An emphasis is set on the impact of the orientation of fibers on this thermal property. [ABSTRACT FROM AUTHOR]

Recent advances have shown the beneficial impact of adding nanoparticles to thermal oil. Diamond and boron nitride nanoparticles have superior thermal conductivity and excellent thermal and optical properties. In the current study, thermal conductivity, specific heat, and rheological behavior of diamond and boron nitride-based hybrid nanofluids in thermal oil are experimentally investigated for 0%, 0.2%, 0.4%, and 0.6% weight concentrations and a wide range of temperatures. The proportion between diamond and boron nitride utilized in the study is 1:1. A two-step method is applied to prepare stable hybrid nanofluids. The obtained data indicate that the hybrid nanofluids' thermal conductivity and specific heat enhance with increasing temperature and weight concentration. Almost 37.4% and 48.1% enhancement is observed in the thermal conductivity and specific heat, respectively, at 65 °C and 0.6% weight concentration. Thermal oil-based hybrid nanofluids display Newtonian behavior at low shear rates and an inverse relationship with temperature. Shear-thinning non-Newtonian behavior is observed at high shear rates and temperatures. A maximum increase in viscosity up to 22.0% is observed at 65 °C and 0.6% wt. concentration. The relative change indicates that all investigated properties have a significant impact, where the increasing trend of thermal conductivity and specific heat with increasing temperature and weight concentration of thermal oil-based hybrid nanofluids make them suitable for high-temperature heat transfer applications. [ABSTRACT FROM AUTHOR]

Koh-i-Noor and other world-famous diamonds such as Hope, Orloff, Great Mogul, Nizam, and Pitt, well-known in the industry as 'Golkonda Diamonds' are very well recognised for their rare colours, large carat sizes, and because of the paucity of nitrogen atoms majority of them have been classified as Type IIa diamonds. These renowned Golkonda diamonds were recovered from placers mined on the banks of the Krishna River in southern India; however, their primary source rocks (either kimberlites or lamproites) remain questioned and untraced. Precise identification of the primary sources of such large-sized, dominantly Type IIa diamonds (i.e., CLIPPIRS) is crucial for understanding their deep mantle origin, nature and timing of magmatism carrying them and essential from economic and geological perspectives. We employed a multidisciplinary approach incorporating xenocrystic mineral composition and bulk-rock geochemistry, field geological and remote sensing (GIS) studies to locate the probable primary sources of these renowned diamonds, know the origin of Type IIa Golkonda diamonds in southern India, and to understand the mechanism and timing of diamond transport and dispersal as placers in the Krishna River basin. Our study rules out the possibility of various lamproite occurrences of the Eastern Dharwar Craton and Banganapalle conglomerates as being sources of Koh-i-Noor and other Golkonda diamonds. The absence of Type IIa diamonds in the highly diamondiferous Late Cretaceous kimberlites of Wajrakarur likewise excludes them as source of Golkonda diamonds. Among southern India's two significant kimberlite fields, i.e., Wajrakarur and Narayanpet, compositions of indicator minerals from the Wajrakarur Kimberlite Field (WKF) reveal their ultimate diamond preservation potential, presence of strong diamondiferous mantle roots and deeper source regions, hence recognising them to be the potential sources of Golkonda diamonds. GIS and remote sensing tools were used to calculate moisture content, vegetation indices, and to locate paleo-channel of the Penner River, which was primarily responsible for the transportation of diamonds from their Mesoproterozoic (ca. 1.1 Ga) source rocks at Wajrakarur to their final sites of recovery, i.e., Kolluru and other mines situated on the banks of the Krishna River. The occurrence of alluvial placer deposits in Krishna River drainage system is analogous to the Orange River drainage system in South Africa. Both areas have diamonds sourced from primary kimberlite pipes, transported by rivers, and deposited in specific areas. Similarities in the origin, mechanism of diamond transport, dispersal and deposition have played a crucial role in significant diamond production from alluvial deposits in Krishna and Orange Rivers. [ABSTRACT FROM AUTHOR]

In multi-electrode devices, charge pulses at all the electrodes are induced concurrently by the motion of the excess charge carriers generated by a single ion. This charge-sharing effect is such that the pulse amplitude at each sensitive electrode depends on the device geometry, its overall electrostatic configuration, and the charge transport properties of the detecting material. Therefore, the cross-analysis of the charge pulses induced at each electrode offers implicit information on the position of the ion impact. In this work, we investigate the two-dimensional position sensitivity of a diamond detector fabricated by deep ion beam lithography. By exploiting the ion beam induced charge technique, the device was exposed to a 2 MeV Li+ ion micro-beam to map the spatial dependence of the charge collection efficiency (CCE) on the nominal micro-beam scanning position. The combination of the CCE maps revealed a two-dimensional position sensitivity of the device with micrometric resolution at the center of the active region. [ABSTRACT FROM AUTHOR]

We employed polarization-sensitive nonlinear optical microscopy to assess crystallinity of diamond microneedles. In the experiment, we mapped the coherent anti-Stokes Raman spectroscopy (CARS) signal in the vicinity of 1332 cm−1 diamond Raman peak over the needle length and demonstrated that the third-order nonlinear optical susceptibility remains the same at both micrometer-sized base and the nanoscale thin apex of the needle. This indicated the single-crystal nature of the diamond needle and allowed us to describe the results of the polarization CARS measurements in terms of the third-order nonlinear susceptibility of diamond. High crystallinity of the needle was also confirmed by measuring the linewidth of the zero-phonon line of the silicon-vacancy centers in diamond. [ABSTRACT FROM AUTHOR]

Polycrystalline diamond compacts (PDCs) with varying amounts of vanadium were successfully sintered. The mechanical and thermal performance tests showed that the abrasion resistance, impact toughness, and thermal resistance increased by 69%, 202.9%, and 30 °C, respectively. The improved performance can be attributed to the solid solution formed by V 8 C 7 with tungsten carbide (WC) as a reinforcing phase, which eliminated interfacial defects, improved residual stress, and reduced the thermal expansion coefficient. In summary, we successfully developed a novel method for fabricating high-performance PDCs to enhance abrasion resistance and thermal stability, while substantially improving impact resistance, and which have remarkable application prospects. [ABSTRACT FROM AUTHOR]

The beamline optics and endstations at branch B of the Versatile Soft X-ray (VerSoX) beamline B07 at Diamond Light Source are described. B07-B provides medium-flux X-rays in the range 45-2200 eV from a bending magnet source, giving access to local electronic structure for atoms of all elements from Li to Y. It has an endstation for high-throughput X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine-structure (NEXAFS) measurements under ultrahigh-vacuum (UHV) conditions. B07-B has a second endstation dedicated to NEXAFS at pressures from UHV to ambient pressure (1 atm). The combination of these endstations permits studies of a wide range of interfaces and materials. The beamline and endstation designs are discussed in detail, as well as their performance and the commissioning process. [ABSTRACT FROM AUTHOR]

Electroplated diamond wire sawing is widely used as a processing method to cut hard and brittle difficult-to-machine materials. Currently, obtaining the sawing capability of diamond wire saw through the wire bow is still difficult. In this paper, a method for calculating the sawing capability of diamond wire saw in real-time based on the wire bow is proposed. The influence of the renewed length per round trip, crystal orientation of sapphire, wire speed, and feed rate on the wire sawing capability has been revealed via slicing experiments. The results indicate that renewing the diamond wire saw, and reducing the wire speed and feed rate can delay the reduction in sawing capability. Furthermore, controlling the value of renewed length per round trip can make the diamond wire saw enter a stable cutting state, in which the capability of the wire saw no longer decreases. The sawing capability of diamond wire saw cutting in the A-plane of the sapphire is smaller than that of the C-plane, and a suitable feed rate or wire speed within the range of sawing parameters studied in this study can avoid a rapid decrease in the sawing capability of the wire saw during the cutting process. The knowledge obtained in this study provides a theoretical basis for monitoring the performance of the wire saw, and guidance for the wire cutting process in semiconductor manufacturing. In the future, it may even be possible to provide real-time performance parameters of diamond wire saw for the digital twin model of wire sawing. [ABSTRACT FROM AUTHOR]

A novel DC-assisted fast hot-pressing (FHP) powder sintering technique was utilized to prepare Al/Diamond composites. Three series of orthogonal experiments were designed and conducted to explore the effects of sintering temperature, sintering pressure, and holding time on the thermal conductivity (TC) and sintering mechanism of an Al-50Diamond composite. Improper sintering temperatures dramatically degraded the TC, as relatively low temperatures (≤520 °C) led to the retention of a large number of pores, while higher temperatures (≥600 °C) caused unavoidable debonding cracks. Excessive pressure (≥100 MPa) induced lattice distortion and the accumulation of dislocations, whereas a prolonged holding time (≥20 min) would most likely cause the Al phase to aggregate into clusters due to surface tension. The optimal process parameters for the preparation of Al-50diamond composites by the FHP method were 560 °C-80 MPa-10 min, corresponding to a density and TC of 3.09 g cm−3 and 527.8 W m−1 K−1, respectively. Structural defects such as pores, dislocations, debonding cracks, and agglomerations within the composite strongly enhance the interfacial thermal resistance (ITR), thereby deteriorating TC performance. Considering the ITR of the binary solid-phase composite, the Hasselman–Johnson model can more accurately predict the TC of Al-50diamond composites for FHP technology under an optimal process with a 3.4% error rate (509.6 W m−1 K−1 to 527.8 W m−1 K−1). The theoretical thermal conductivity of the binary composites estimated by data modeling (Hasselman–Johnson Model, etc.) matches well with the actual thermal conductivity of the sintered samples using the FHP method. [ABSTRACT FROM AUTHOR]

For single crystal diamond (SCD) to gain practical use in technical applications including solid state electronics, thin (< $1 ~\mu \text{m}$), doped epitaxial SCD layers with very low (<1 nm) surface roughness are required. Conventional SCD chemical mechanical polishing (CMP) processes are insufficient to meet the requirements of such applications because the material removal rate (MRR) is often characterized inappropriately, and the material removal uniformity is seldom considered. In this study, chemical vapor deposition (CVD) growth of two lightly boron doped (p-) epilayers was performed on 3° misoriented (100) high pressure high temperature substrates of 4.5 x $4.5 mm^{2}$ area. A subsequent 8-hour oxidative CMP process utilizing potassium permanganate and a novel self-leveling holder design decreased the average surface roughness from 3.83 nm and 1.57 nm to 0.20 nm and 0.16 nm for the two samples, respectively. MRRs were determined by evaluating five circular wear monitor structures in each sample by atomic force microscopy before and after the CMP process. The average MRRs were found to be 38.6 nm/hr and 37.3 nm/hr for the two samples. The purpose of this study is to demonstrate a CMP process suitable for polishing thin SCD epilayers to meet the needs of solid-state electronics applications. [ABSTRACT FROM AUTHOR]

Global bandwidth scarcity and escalation in energy consumption in the next-generation wireless communication sector has motivated the research and exploration of non-orthogonal multiple access (NOMA) powered with radio frequency (RF) energy harvesting. With the motivation of taking advantage of energy efficiency (EE) as well as spectral efficiency, this article focuses on analysing the performance of an autonomous and energy-efficient RF-powered multi-device diamond relay network in an Internet of things (IoT) environment using an improved adaptive NOMA (A-NOMA) protocol. Here, the IoT relay devices within a certain selection range employ NOMA, and the rest adopt orthogonal multiple access (OMA) functionality for information decoding. A-NOMA transmission technique determines the best multiple access protocol on the basis of maximum achievable sum rate (ASR). Closed form expressions of ASR and EE have been derived under Rayleigh fading environment and validated through extensive Monte Carlo simulations. Using the expressions, the overall sum rate of the proposed system has been evaluated and a noticeable improvement in ASR has been obtained for the investigated framework over similar system models devised using OMA and NOMA. In addition, bit error rate analysis has been carried out and compared with the existing benchmarks. Lastly, an in-depth analysis on EE with respect to ASR has also been performed. Simulation results demonstrate the effectiveness of our investigated model over the existing state of art and unveil interesting trade-off between EE and ASR. [ABSTRACT FROM AUTHOR]

AISI 420 is primarily used for optic molds manufactured through ultraprecision machining with single-crystal diamond tools. Tool wear rapidly occurs due to the diffusion of diamond and iron atoms when cutting ferrous metals with diamond tools. In the machining of optic molds, the diamond tool is uniformly replaced, regardless of the tool status after use for some time due to the difficulty in predicting tool life. This practice results in the wastage of expensive single-crystal diamond tools and reduces productivity. This study addressed the aforementioned issue by developing a tool-life model through theoretical analysis of the effective contact ratio between the tool and the workpiece and a cutting experiment with high-frequency ultrasonic vibration. In addition, the effectiveness of ultrasonic vibration cutting on the suppression of diamond tool wear was demonstrated by measuring tool wear after the cutting experiments. [ABSTRACT FROM AUTHOR]

The corrosion resistance of Cu/Diamond composite materials, a combination of copper and diamond, was investigated in aqueous conditions. A 3.5 % NaCl neutral salt spray was employed to assess the corrosion performance of the composite, considering factors such as surface appearance, corrosion rate, and corrosion depth. The results revealed that corrosion predominantly occurred within the copper matrix, while the diamond and interface components remained resistant to corrosion. Micro-galvanic corrosion was identified as the primary corrosion mechanism. Additionally, the incorporation of 5 % diamond particles led to a notable improvement in corrosion resistance, reaching 93.7 %. Although the salt spray environment did induce some changes in the composite surface, it did not significantly impact the overall properties of the composite. [ABSTRACT FROM AUTHOR]

In this study, diamond/silicon carbide (SiC) composites were prepared by liquid Si infiltration. The effects of the infiltration temperature on the densification, diamond graphitization, and thermal conductivity of the composites were investigated. The effects of the diamond content on the thermal conductivity and bending strength were also explored. X‐ray diffraction and Raman spectroscopy detected diamond graphitization at an infiltration temperature of 1480°C. Almost no graphitized diamond was observed due to reactions between silicon and carbon to form SiC at infiltration temperatures higher than 1480°C. As the infiltration temperature increased, graphitized diamond was consumed, and the thermal conductivity of the composite rose. The thermal conductivity and bending strength of the composites depended on the diamond content, reaching values of 257 W/m K and 237 MPa, respectively, for the sample with a diamond content of 17.9 vol.%. The higher bending strength was mainly ascribed to the high diamond content and well‐bonded interface. [ABSTRACT FROM AUTHOR]

When Harley Quinn (Margot Robbie) dressed as Lorelei (Marilyn Monroe) from 1953 film Gentlemen Prefer Blondes performs "Diamonds are a Girl's Best Friend" in Cathy Yan's 2020 film Birds of Prey (and the Fantabulous Emancipation of One Harley Quinn), links are drawn between 70 years of film history and women's representation on screen. In this article, I put various iterations of "Diamonds" into dialogue to explore how this moment in Birds of Prey might be understood. I consider this scene as central to understanding Quinn's "emancipation," with the representation of women's security and control over their lives key themes in the history of this scene. The return to this song throughout the histories of film and video enables a sense of solidarity across time, acknowledging the systemic problems that remain unresolved, and contemplation of this can alter the ways we understand characters and texts, past, present, and future. [ABSTRACT FROM AUTHOR]

Here we have performed single-crystal X-ray diffraction (SCXRD) experiments on two high-quality crystal platelets of (Al,Fe)-bearing bridgmanite (Mg0.88 F e 0.065 3 + F e 0.035 2 + Al0.03)(Al0.11Si0.90)O3 (Fe10-Al14-Bgm) up to 64.6(6) GPa at room temperature in a Boehler-Almax type diamond-anvil cell. Refinements on the collected SCXRD patterns reveal reliable structural information of single-crystal Fe10-Al14-Bgm, including unit-cell parameters, atomic coordinates, and anisotropic displacement parameters. Together with Mössbauer and electron microprobe analyses, our best single-crystal refinement model indicates that the sample contains ~6.5 mol% Fe3+, 3.5 mol% Fe2+, and 3 mol% Al3+ in the large pseudo-dodecahedral site (A site), and ~11 mol% Al3+ in the small octahedral site (B site). This may indicate that Al3+ in bridgmanite preferentially occupies the B site. Our results show that the compression of Fe10-Al14-Bgm with pressure causes monotonical decreases in the volumes of AO12 pseudo-dodecahedron and BO6 octahedron (VA and VB, respectively) as well as the associated A-O and B-O bond lengths. The interatomic angles of B-O1-B and B-O2-B decrease from 145.2–145.8° at 4.2(1) GPa to 143.3–143.5° at 64.6(6) GPa. Quantitative calculations of octahedral tilting angles (Φ) show that Φ increases smoothly with pressure. We found a linear relationship between the polyhedral volume ratio and the Φ in the bridgmanite with different compositions: VA/VB = –0.049Φ + 5.549. Our results indicate an increased distortion of the Fe10-Al14-Bgm structure with pressure, which might be related to the distortion of A-site Fe2+. The local environmental changes of A-site Fe2+ in bridgmanite could explain previous results on the hyperfine parameters, abnormal lattice thermal conductivity, mean force constant of iron bonds and other physical properties, which in turn provide insights into our understanding on the geophysics and geochemistry of the planet. [ABSTRACT FROM AUTHOR]

Diamond possesses extremely excellent properties, which make it a potentially transformative material in an extensive range of applications. Herein, diamonds were synthesized in a FeNiCo–C system with B2S3 as an additive by a temperature-gradient growth method at high temperature and high pressure (HPHT) conditions. The effects of the B2S3 additive in the FeNiCo–C system on diamond crystallization were characterized using Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements. FTIR result shows the presence of positive-charged N+ in the diamond crystal synthesized with the B2S3 additive, and its concentration was estimated to be around 30 ppm. Moreover, the XPS measurements confirm that N+ can combine with boron to form a B–N bond. Furthermore, the Hall effect result indicates that the resistivity of the diamond crystal synthesized with B2S3 was reduced to 3.89 × 10 Ω cm, whereas, the resistivity of the diamond synthesized with the same weight of B2S3 additive along with Ti/Cu as the nitrogen removal agent dropped sharply to 2.51 × 10−1 Ω cm. [ABSTRACT FROM AUTHOR]

Single-crystal diamond possesses exceptional physical and optical properties, rendering it an ideal platform for integrated quantum optics. The direct integration of broadband-sensitive and high-performance single-photon detectors on diamond holds significant implications for the realization of integrated diamond quantum optical circuits. In this study, we polished the diamond surface with RMS (root mean square) below 0.6 nm suitable for the deposition and patterning of NbN thin films through ion beam etching. Subsequently, we fabricated superconducting nanowire single-photon detectors directly on the polished diamond substrates and characterized for their electrical and optical properties. The NbN-SNSPD exhibited a high critical current density (2 MA cm−2), a saturated quantum efficiency (QE) below 2.5 K, and a maximum value of QE up to 88% at 4 K. These findings offer a promising solution for fully integrated quantum optical chips on single-crystal diamond substrates. [ABSTRACT FROM AUTHOR]

The multilevel encoding (MLE) scheme is an effective method for improving the anticounterfeiting encryption capabilities of physically unclonable functions (PUFs). However, owing to the correlation between encoding layers, the encoding capacity (EC) is difficult to improve by orders of magnitude. Herein, four noncorrelated structures in the diamond crystal structure (carbon–carbon single bond, defect luminescence structures, spin structures, and electron energy distribution structures) are considered for MLE. First, the microdiamonds containing nitrogen‐vacancy (NV) color centers are embedded into polydimethylsiloxane (PDMS) to fabricate PUFs. Using an optical imaging system, four codable images of four noncorrelated structures are read. The noncorrelation of the four‐level encoding structure is verified by calculating the Hamming distance (0.496 ± 0.02). The results show that EC exponentially improves to 24×10 000/(100 pixels)2. Furthermore, the encoding method based on the energy level does not depend on physical structure parameters, such as the size and position of the spin structure. Thus, it is protected from structural modeling attacks, resulting in high security. Moreover, PUF labels based on PDMS flexible substrates can be employed for various flexible applications. In the proposed scheme, the information is encrypted by a four‐level two‐dimensional (2D) barcode and decoded by self‐developed PUF authentication software. The proposed scheme presents a way for developing next‐generation PUFs with super‐high EC. [ABSTRACT FROM AUTHOR]

Diamonds produced using chemical vapor deposition (CVD) have found many applications in various fields of science and technology. Many applications involve polycrystalline CVD diamond films of micron thicknesses. However, a variety of optical, thermal, mechanical, and radiation sensing applications require more bulky CVD diamond samples. We report the results of a magnetic resonance and structural study of a thick, sizable polycrystalline CVD diamond disc, both as-prepared and treated with e-beam irradiation/high-temperature annealing, as well as gamma irradiation. The combination of various magnetic resonance techniques reveals and enables the attribution of a plentiful collection of paramagnetic defects of doublet and triplet spin origin. Analysis of spectra, electron, and nuclear spin relaxation, as well as nuclear spin diffusion, supports the conclusion of significant macro- and micro-inhomogeneities in the distribution of nitrogen-related defects. [ABSTRACT FROM AUTHOR]