Diamond Crystals Research Articles

The morphological analysis of crystalline methadone: a novel combination of microscopy techniques

The aim: to evaluate combined microscopy techniques for determining the morphological and optical properties of methadone hydrochloride (MDN) crystals.
 Materials and methods: MDN crystal formation was optimized using a closed container method and crystals were characterized using polarized light microscope (PLM), scanning electron microscopy (SEM) and confocal microscopy (CM). SEM and CM were used to determine MDN crystal thickness and study its relationship with crystal retardation colours using the Michel-Levy Birefringence approach.
 Results: Dimensions (mean±SD) of diamond shaped MDN crystals were confirmed using SEM and CM. Crystals were 46.4±15.2 Vs 32.0±8.3 µm long, 28.03±8.2 Vs 20.85±5.5 µm wide, and 6.62±2.9 Vs 9.6±4.6 µm thick, respectively. There were significant differences between SEM and CM thickness measurements (U=1283, p<0.05), as the SEM exhibited thinner diamond crystals. The combined use of PLM and Michel-Levy chart enabled the observation of a predominantly yellow coloured MDN crystal, mean thickness at (428 nm) mean retardation value.
 Conclusion: The SEM was superior and successfully determined MDN crystal dimensions for the first time, whilst the CM results were affected by the Rhodamine dye staining process used for visualisation. The qualitative analysis of the crystallinity status of methadone hydrochloride optimally achieved using a combination of PLM and SEM techniques

Growth Story of One Diamond: A Window to the Lithospheric Mantle

A diamond plate cut out of a transparent, colorless octahedral diamond crystal of gem quality, with a small chromite inclusion in the core, sampled from the XXIII CPSU Congress kimberlite (Yakutia, Mirny kimberlite field, vicinities of Mirny city), has been studied by several combined methods: absorption spectroscopy at different wavelengths (UV-visible, near- and mid-IR); photoluminescence, cathodoluminescence, and Raman spectroscopy (local version) and lattice strain mapping; birefringence in cross-polarized light; and etching. The diamond plate demonstrates a complex growth history consisting of four stages: nucleation and growth to an octahedron → habit change to a cuboid → habit change to octahedron-1 → habit change to octahedron-2. The growth history of the diamond records changes in the crystallization conditions at each stage. The revealed heterogeneity of the crystal structure is associated with the distribution and speciation of nitrogen defects. The results of this study have implications for the information value of different techniques as to the diamond structure defects, as well as for the as yet poorly known evolution of the subcontinental lithospheric mantle in the Siberian craton, recorded in the multistage growth of the diamond crystal. At the time of writing, reconstructing the conditions for each stage is difficult. Meanwhile, finding ways for such reconstruction is indispensable for a better understanding of diamond genesis, and details of the lithosphere history.

Structural Evolution of C60 Molecular Crystal Predicted by Neural Network Potential

AbstractThe preparation of fullerene and a wide range of derivatives has attracted much attention in past decades. Understanding the structural evolution starting from fullerene is critical to guide the experimental exploration but has been paid less attention yet. Using ab initio molecular dynamics or global structural search algorithm accompanied with density functional theory calculations can give a glance of the potential energy surface (PES), but suffers high cost and low efficiency. Herein, by using neural network potentials and stochastic surface walking global structural search method, an accelerated energy calculation, and the higher efficient PES mapping starting from C60 molecular crystal are reported. The structural evolution is found to follow an order of molecular crystal → polymers → opened caged ordered structures → 3D) curved carbon and graphite under zero pressure. Under high pressures, e.g., 50 GPa, the evolution follows a pathway of fullerene → sp2 and sp3 hybrid carbon → sp3 amorphous carbon and crystal diamond. The electronic property calculation of the obtained structures in the evolution pathway shows a band gap depending on the order parameter of the generated structures, suggesting that more novel carbons can be potentially prepared in experiments, starting from C60.

Optimal direction and propagation of mid-IR light inside rough and polished diamonds for highly-sensitive transmission measurements of nitrogen content

Optical transmission/absorption measurements in diamond provide a way for determining content of basic nitrogen defects, with their concentrations varying in different crystals by many orders of magnitude. In a traditional scheme of transmission measurement in many diamond crystals only a small fraction of incident light is transmitted and detected due to light refraction and multiple reflections. This significantly reduces signal-to-noise ratio, narrows the dynamic range of measured signal magnitudes and the corresponding range of measurable defects concentrations. In this work optimal input/output points and optical propagation paths of mid-IR light inside most characteristic forms of rough and faceted diamonds were searched and analyzed. Practical acquisition recommendations and measurement configurations are proposed, enabling to expand signal dynamic range by acquiring multiple mid-IR light reflection/transmission replica, using an integrating sphere and immersion material.

Structural Peculiarities of As-Grown Single Crystals of Boron-Doped Diamond

Structural Peculiarities of As-Grown Single Crystals of Boron-Doped Diamond

Selective Deposition of Mo2C-Containing Coatings on {100} Facets of Synthetic Diamond Crystals.

An efficient way to improve the properties of metal–diamond composites (mechanical strength, wear resistance, thermal conductivity) is the preliminary modification of the diamond surface to improve its wettability by the metal matrix. In the present work, Mo2C-containing coatings were deposited on the diamond crystals under different conditions: hot pressing (atmosphere of argon), spark plasma sintering (forevacuum), and annealing in air. The influence of the sintering parameters on the morphology and phase composition of the coatings deposited on diamond was studied. Mo2C-containing coatings were selectively deposited on the facets of synthetic diamond microcrystals by annealing of the latter with a molybdenum powder. Experiments were carried out to deposit coatings under different conditions: during hot pressing (argon atmosphere), spark plasma sintering (forevacuum), and annealing in air. The process parameters were the temperature, holding time, and concentration of molybdenum in the initial mixture. Experiments with a pre-oxidized molybdenum powder were also conducted. The coated diamond crystals were investigated by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The deposition was enabled by the gas phase transport of molybdenum dioxide, MoO2, contained in the starting powder. The following sequence of the coating formation stages was proposed. First, MoO2 sublimes and is adsorbed mainly on the {100} facets of diamond. Then, it is reduced to metallic molybdenum by carbon of the diamond, which further reacts with carbon to form the Mo2C carbide phase. These processes occurred during treatment of the mixtures in the hot press and the spark plasma sintering facility. When the mixture was annealed in air, no selective deposition was observed. During annealing, MoO3 particles adhered to the diamond surface.

Thermal history of diamond from Arkhangelskaya and Karpinsky-I kimberlite pipes

This work studies and compares the main morphological, structural, and mineralogical features of 350 diamond crystals from the Karpinsky-I and 300 crystals of the Arkhangelskaya kimberlite pipes. The share of crystals of octahedral habit together with individual crystals of transitional forms with sheaf-like and splintery striation is higher in the Arkhangelskaya pipe and makes 15 %. The share of cuboids and tetrahexahedroids is higher in the Karpinsky-I pipe and stands at 14 %. The share of dodecahedroids in the Arkhangelskaya and Karpinsky-I pipes are 60 % and 50 %, respectively. The indicator role of the nitrogen-vacancy N3 center active in absorption and luminescence is shown. Crystals with the N3 absorption system have predominantly octahedral habit or dissolution forms derived from the octahedra. Their thermal history is the most complex. Absorption bands of the lowest-temperature hydrogen-containing defects (3050, 3144, 3154, 3188, 3310 cm−1, 1388, 1407, 1432, 1456, 1465, 1503, 1551, 1563 cm−1), are typical for crystals without N3 system, where in the absorption spectra nitrogen is in the form of low-temperature A and C defects. The above mentioned bands are registered in the spectra of 16 % and 42 % of crystals from the Arkhangelskaya and Karpinsky-I pipes, respectively. The diamond of the studied deposits is unique in the minimum temperature (duration) of natural annealing. Based on a set of features, three populations of crystals were distinguished, differing in growth conditions, post-growth, and thermal histories. The established regularities prove the multi-stage formation of diamond deposits in the north of the East European Platform and significant differences from the diamonds of the Western Cisurals. The results suggest the possibility of the existence of primary deposits dominated by diamonds from one of the identified populations.

Genetic link between saline and carbonatitic mantle fluids: The system NaCl-CaCO3-MgCO3 ± H2O ± Fe0 at 6 GPa

Melt inclusions in kimberlitic minerals and diamonds indicate that chlorides are important constituents of mantle carbonatite melts. Besides, alkaline chlorides are important constituents of saline high-density fluids (HDFs) found in diamonds from kimberlites and placers around the world. Continuous compositional variations suggest that saline and carbonatitic HDFs could be genetically linked. However, the essence of this link remains unclear owing to the lack of data on phase relations in the chloride-carbonate systems under pressure. Here we studied subsolidus and melting phase relations in the system NaCl–CaCO3–MgCO3 at 6 GPa and 1000–1600 °C using a Kawai-type multianvil press. We found that at 1000 °C, subsolidus assemblage consists of halite, magnesite, and aragonite. At higher temperatures, the stabilization of dolomite splits the subsolidus area into two partial ternary fields: halite + magnesite + dolomite and halite + dolomite + aragonite. The minimum on the liquidus surface corresponds to the halite-dolomite-aragonite ternary eutectic, situated at 1100 °C. The eutectic melt has Ca# 89 and contains 30 wt.% NaCl (26 mol% 2NaCl). The system has two ternary peritectics: halite + dolomite = magnesite + liquid located near the ternary eutectic and magnesite + dolomite = Mg-dolomite + liquid situated between 1300 and 1400 °C. Although under dry conditions incipient melting yields carbonate-dominated melt, the addition of water facilitates the fusion of NaCl and expands the liquid field to NaCl-rich compositions with up to 70 wt.% NaCl. The obtained results favor the idea that hydrous saline melts/fluids (brines) found as inclusions in diamonds could be a lower temperature derivative of mantle carbonatite melts and disagree with the hypothesis on chloride melt generation owing to the chloride-carbonate liquid immiscibility since no such immiscibility was established. We also studied the interaction of the NaCl–CaCO3–MgCO3 system with iron metal and found that carbonate reduction produces C-bearing species (Fe0, Fe-C melt, Fe3C, Fe7C3, C0) and wüstite containing Na2O, CaO, and MgO. Besides, a carbonate chloride compound, Ca2Cl2CO3, was established among the reaction products. The interaction between NaCl-bearing carbonate melt shifts its composition toward Mg-poor and NaCl-rich. Given the above, an alternative hypothesis can be proposed, according to which the interaction of alkaline chloride-bearing carbonate melts formed in the subduction zones with the reduced mantle should be accompanied by diamond crystallization and shift the composition of the melt from carbonatitic to alkali-rich saline.

Effect of phosphorus ion implantation on electrical conductivity and local lattice distortions in diamond

In this work, phosphorus ions have been implanted with various doses at an energy 100 keV on single crystal (100) diamond. We try to understand the local lattice distortions (disorder) induced in the implanted layer post annealing (at 850 °C) as a result of ion impact with the help of out-of-plane as well as in-plane XRD techniques and its corresponding effect on the electrical conductivity in diamond crystal. While a low dose of 1014cm−2 increases the lattice parameter along the out-of-plane direction and leads to formation of isolated point defects (mostly interstitials) in the lattice without introducing much disorder, a moderate dose of 1015cm−2 initiates the process of clustering of these defects in the implanted/defected layer. An out-of-plane tensile strain that is present in low dose case is eventually released with moderate dose implantations. With high doses of phosphorus in diamond, the crystallinity in the implanted layer drops, the damage propagates to the extent that it forms small amorphous pockets within this defected layer; although the lattice is not completely amorphous as it still retains the long range order as confirmed from X-ray absorption results. Our data indicate that the electrical transport in diamond is mainly due to substitutional phosphorus when implanted at low dose of 1014cm−2 and also highlights that damage or ‘localized amorphization’ takes place at a critical implantation dose of 1016cm−2 and therefore the critical phosphorus ion dose of 1015cm−2 (in 100 keV energy regime) i.e. a damage threshold of 8 × 1021vacancies/cm3 is the limit beyond which chances of amorphization is prevalent and the electronic properties in diamond are solely due to sp3 bond breakage.

Development and IR spectroscopic Analysis of Composite Materials Based on Poly(Methyl Methacrylate) and Chitosan

Poly (methyl methacrylate) (PMMA) and chitosan composites were synthesized by means of the mechanochemical method. In addition, PMMA–chitosan films were obtained in polar (water) and non-polar (benzene) solvents. Obtained polymer composites were analyzed by the Fourier transform infrared spectroscopy method using the ATR attachment with diamond crystal. The presence of intermolecular hydrogen bonds in formation of PMMA and chitosan polymer composites was shown. С=О group of PMMA and OH and NH2 groups of chitosan molecule take part in the formation of hydrogen bonds.

Optical properties of He+-implanted and diamond blade-diced terbium gallium garnet crystal planar and ridge waveguides

Terbium gallium garnet (Tb3Ga5O12, TGG) crystal can be used to fabricate various magneto-optical devices due to its optimal Faraday effect. In this work, 400-keV He+ ions with a fluence of 6.0 × 1016 ions/cm2 are irradiated into the TGG crystal for the planar waveguide formation. The precise diamond blade dicing with a rotation speed of 2 × 104 rpm and a cutting velocity of 0.1 mm/s is performed on the He+-implanted TGG planar waveguide for the ridge structure. The dark-mode spectrum of the He+-implanted TGG planar waveguide is measured by the prism-coupling method, thereby obtaining the relationship between the reflected light intensity and the effective refractive index. The refractive index profile of the planar waveguide is reconstructed by the reflectivity calculation method. The near-field light intensity distribution of the planar waveguide and the ridge waveguide are recorded by the end-face coupling method. The He+-implanted and diamond blade-diced TGG crystal planar and ridge waveguides are promising candidates for integrated magneto-optical devices.

Crystal orientation and material type related suppression to the graphitization wear of micro diamond tool

According to the Hencky stress theorem and J-C constitutive equation, a cutting force model is established for the diamond turning process when using micro diamond tool, through which the stress distributions on tool rake face and flank face are calculated. A stress model is further developed to calculate the stress distribution on the cutting edge region by using the stress intensity factor theory of fracture mechanics, into which the influences of crystal orientation of rake and flank faces are integrated. With consideration of elastic modulus and defect density of diamond crystal, the critical stress for graphitization of diamond tool is also deduced in response to different crystal orientations and types of diamond material. Finally, cutting experiments are performed to validate the theoretical predictions. Results show that the experimental observations agree well with the theoretical predictions. Such satisfactory consistency confirms that the natural cape Ia diamond as tool material and the (100) crystal plane as tool faces can effectively inhibit the graphitization wear of micro diamond tool.

Reduced photothermal heating in diamonds enriched with H3 point defects

Solid-state laser refrigeration of semiconductors remains an outstanding experimental challenge. In this work, we show that, following excitation with a laser wavelength of 532 nm, bulk diamond crystals doped with H3 centers both emit efficient up-conversion (anti-Stokes) photoluminescence and also show significantly reduced photothermal heating relative to crystals doped with nitrogen–vacancy (NV) centers. The H3 center in diamond is a highly photostable defect that avoids bleaching at high laser irradiances of 10–70 MW/cm2 and has been shown to exhibit laser action, tunable over the visible band of 500–600 nm. The observed reduction of photothermal heating arises due to a decrease in the concentration of absorbing point defects, including NV-centers. These results encourage future exploration of techniques for H3 enrichment in diamonds under high-pressure, high-temperature conditions for the simultaneous anti-Stokes fluorescence cooling and radiation balanced lasing in semiconductor materials. Reducing photothermal heating in diamond through the formation of H3 centers also opens up new possibilities in quantum sensing via optically detected magnetic resonance spectroscopy at ambient conditions.

Effect of the codoping of N–H–O on the growth characteristics and defects of diamonds under high temperature and high pressure

Diamond crystals were synthesized with different doping proportions of N–H–O at 5.5 GPa–7.1 GPa and 1370 °C–1450 °C. With the increase in the N–H–O doping ratio, the crystal growth rate decreased, the temperature and pressure conditions required for diamond nucleation became increasingly stringent, and the diamond crystallization process was affected. [111] became the dominant plane of diamonds; surface morphology became block-like; and growth texture, stacking faults, and etch pits increased. The diamond crystals had a two-dimensional growth habit. Increasing the doping concentration also increased the amount of N that entered the diamond crystals as confirmed via Fourier transform infrared spectroscopy. However, crystal quality gradually deteriorated as verified by the red-shifting of Raman peak positions and the widening of the Raman full width at half maximum. With the increase in the doping ratio, the photoluminescence property of the diamond crystals also drastically changed. The intensity of the N vacancy center of the diamond crystals changed, and several Ni-related defect centers, such as the NE1 and NE3 centers, appeared. Diamond synthesis in N–H–O-bearing fluid provides important information for deepening our understanding of the growth characteristics of diamonds in complex systems and the formation mechanism of natural diamonds, which are almost always N-rich and full of various defect centers. Meanwhile, this study proved that the type of defect centers in diamond crystals could be regulated by controlling the N–H–O impurity contents of the synthesis system.

Microstructure changes of diamond and amorphous carbon under shear conditions

Diamond is an important tool material in ultra-precision machining. Many researches are conducted about the amorphous carbon (a-C) generated during diamond grinding. However, most of them are not able to clarify the transition mechanism of diamond crystal, which just focus on the amorphization results. This paper divides the amorphization process into three parts: peel, disorder and steady state based on the simulation results of molecular dynamics (MD) to obtain a deep understanding of the transitions under different shear conditions. The change laws of a-C composition in each part are obtained by mathematical deductions and the critical strains for transitions are calculated, finding that critical strain can unify the relationships between physical state, material properties, and amorphization in diamond. In addition, the similarities of microstructures between different a-C are analyzed to accelerate the MD modeling of fluidic a-C (fa-C) obtained by the grinding process. The results prove that different solid a-C (sa-C) convert into the same structure under the specific shear condition, but the conversion rate depends on sa-C density.

Ultrafast opto-magnetic effects induced by nitrogen-vacancy centers in diamond crystals

The current generation of quantum sensing technologies using color centers in diamond crystals is primarily based on the principle that the resonant microwave frequency of the luminescence between quantum levels of the nitrogen-vacancy (NV) center varies with temperature and electric and magnetic fields. This principle enables us to measure, for instance, magnetic and electric fields, as well as local temperature with nanometer resolution in conjunction with a scanning probe microscope (SPM). However, the time resolution of conventional quantum sensing technologies has been limited to microseconds due to the limited luminescence lifetime. Here, we investigate ultrafast opto-magnetic effects in diamond crystals containing NV centers to improve the time resolution of quantum sensing to sub-picosecond time scales. The spin ensemble from diamond NV centers induces an inverse Cotton–Mouton effect (ICME) in the form of a sub-picosecond optical response in a femtosecond pump–probe measurement. The helicity and quadratic power dependence of the ICME can be interpreted as a second-order opto-magnetic effect in which ensembles of NV electron spins act as a source for the ICME. The results provide fundamental guidelines for enabling high-resolution spatial-time quantum sensing technologies when combined with SPM techniques.

Protogenetic clinopyroxene inclusions in diamond and Nd diffusion modeling—Implications for diamond dating

Abstract Diamonds are witnesses of processes that have operated in Earth's mantle over more than 3 b.y. Essential to our understanding of these processes is the determination of diamond crystallization ages. These cannot be directly determined on diamond, but they can be calculated using radiogenic isotopic systematics of suitable minerals included in a diamond. This method relies on the assumption that the mineral inclusions were in isotopic equilibrium with the diamond-forming medium. We evaluated the validity of Sm-Nd ages yielded by clinopyroxene inclusions by combining crystallographic orientation analyses and Nd diffusion modeling at the relevant conditions for Earth's cratonic mantle. We investigated the crystallographic orientation relationships (CORs) for 54 clinopyroxene inclusions within 18 diamonds from South Africa and Siberia. Clinopyroxene inclusions in some diamonds showed specific CORs with their hosts, indicating possible syngenesis. Other samples had clusters of clinopyroxene inclusions sharing the same orientation but no specific orientation relative to their hosts, indicating that the inclusions are older than the diamond (i.e., they are protogenetic). Diffusion modeling in the temperature range typical for lithospheric diamonds (900–1400 °C) showed that resetting of the Sm-Nd isotopic system in clinopyroxene grains larger than 0.05 mm requires geologically long interaction with the diamond-forming fluid/melt (>3.5 m.y. at average temperature of ~1150 °C). Depending on inclusion size and temperature regime, protogenetic clinopyroxene inclusions may not fully reequilibrate during diamond-formation events. We suggest that small clinopyroxene inclusions (<0.2 mm) that equilibrated at temperatures higher than 1050–1080 °C may be the most suitable for age determinations.

Complete analysis of dislocations in single crystal diamonds

In this study, we applied dislocation analysis to X-ray topography images to identify the complete dislocation information for two typical high-pressure high-temperature diamond crystals, IIa and Ib. Almost all dislocation line vectors of both crystals were identified for the first time. For IIa crystal, it was confirmed that up to 84% of the dislocations have 〈101〉 vectors. For Ib crystal, up to 71% of the dislocations have 〈112〉, 〈121〉, and 〈211〉 vectors. Both [110] and [1-10] with zero components of the c-axis are the major Burgers vectors. Regarding the types of dislocation, the major types were edge types, which were approximately 47% and 65% for IIa and Ib crystals, respectively. In addition, screw, 60° and 73° type on the IIa, and 30°, 35°, and 73° type on Ib were identified. Complete analysis of dislocations will give important information for the diamond growth and reduction of the dislocations.

Micro-scale abrasion investigations of single-crystal diamonds using nano-polycrystalline diamond wheels

A small grinding wheel of 3.2 mm in diameter was prepared from nano-polycrystalline diamond (NPD) obtained by direct conversion sintering under high pressure and high temperature. Using this NPD wheel as a grinding blade, a new useful method for investigating the micro-scale abrasive properties of single-crystal diamonds was developed. Since NPD has an extremely high hardness of about 130 GPa, the abrasive properties of various natural and synthetic single-crystal diamonds, whose hardness is usually around 70 to 125 GPa, can be appropriately evaluated. In addition, since the wheel diameter is very small, it is possible to measure the abrasion resistance in a minute region of several tens of μm in a diamond crystal. It was confirmed that the method can accurately evaluate the abrasive properties of minute regions of single-crystal diamonds using synthetic type IIa diamond. It was also demonstrated that it is possible to investigate how the abrasive properties of synthetic type Ib and natural type Ia diamonds change depending on the distribution of impurities or crystal defects in the crystals.

Enhanced stimulated Brillouin scattering utilizing Raman conversion in diamond

Cascaded Brillouin lasers based on guided-wave structures are applied across a range of important fields such as optical communications, microwave photonics, and sensing. However, restricted by the volume and available transmission range of the gain medium, the power output and wavelength diversity of guided-wave Brillouin devices are somewhat limited. In this work, we report the design and development of a cascaded Brillouin laser based utilizing a free-space optical layout with a diamond crystal as the Brillouin gain medium. A quasi-continuous-wave, 1 μm laser was used as the pump laser, and Raman wavelength conversion is used as an intermediate process to facilitate stimulated Brillouin scattering with a low threshold. When the output transmission of the diamond cavity is 0.37% and the incident pump power is 220 W, cascading of the Brillouin–Stokes field to the eighth Stokes and the seventh anti-Stokes orders was observed. By adjusting the cavity length, the order of the cascaded Brillouin laser output is controlled. A comprehensive analysis of the Brillouin generation process and the cascade of Stokes orders is undertaken for different incident pump powers and cavity lengths. This work is expected to enable practical applications of high-power Brillouin lasers and Brillouin frequency combs.