Properties Of Diamond Research Articles

Diamond etching with near-zero micromasking

The outstanding material properties of single-crystal diamond have been the origin of the long-standing interest in its exploitation for engineering of high-performance micro- and nanosystems. Etching and patterning diamond have proven challenging due to the hardness and chemical resistance of the material. In this work, the patterned etching process of single-crystal diamond has been investigated using the inductively coupled plasma etching technique. In order to avoid the micromasking phenomenon caused by the metal mask, this paper adopts the Ar/O2-Ar/Cl2/BCl3 two-step cycle etching process and investigates the effect of the Cl2/BCl3 gas ratio on the bottom morphology of single-crystal diamond grid grooves. A theoretical explanation is provided for the use of chlorine-based gases to eliminate micromasking and achieve a smooth etching surface. Finally, an Ar/O₂-Ar/Cl₂/BCl3 cyclic etching process for patterning single-crystal diamond with near-zero micromasking has been developed.

Microcrystalline and nanocrystalline structure of diamond films grown by MPCVD with nitrogen additions: Study of transitional synthesis conditions

This research explores the complex influence of nitrogen concentration and substrate temperature on the resultant properties of polycrystalline diamond (PCD) films grown by microwave plasma chemical vapor deposition (CVD). In particular, we investigated the growth parameters to find the exact conditions for changing the morphology of the resulting film from microcrystalline (MCD) to nanocrystalline (NCD). A series of 2 µm-thick polycrystalline diamond films was grown on Si substrates in methane-hydrogen–nitrogen gas mixtures with varied: (i) nitrogen concentration (0–2 %) and (ii) substrate temperature (700–1050 °C). Comprehensive characterization techniques, including scanning electron microscopy (SEM), micro-Raman spectroscopy, and X-ray diffraction, were employed to assess the morphological, structural, and spectroscopic properties of the films. The study reveals that even minor additions of nitrogen significantly modulate secondary nucleation, impacting both film morphology and phase composition. Furthermore, substrate temperature emerges as another critical parameter, influencing the growth kinetics and crystallite size. The comparison of the characteristics of grown PCD films allowed us to find conditions for the formation of NCD films with minimal surface roughness and maximal growth rate: nitrogen concentration [N2] ≈ 0.2–0.5 % and temperature T ≈ 850–900 °C. These findings can be used to optimize the CVD synthesis parameters of PCD films for applications as protective or friction-reducing layers, as well as for superhard cutting tools and optical devices.

Insights on the Bonding Mechanism, Electronic and Optical Properties of Diamond Nanothread-Polymer and Cement-Boron Nitride Nanotube Composites.

The success of composite materials is attributed to the nature of bonding at the nanoscale and the resulting structure-related properties. This study reports on the interaction, electronic, and optical properties of diamond nanothread/polymers (cellulose and epoxy) and boron nitride nanotube/calcium silicate hydrate composites using density functional theory modeling. Our findings indicate that the interaction between the nanothread and polymer is due to van der Waals-type bonding. Minor modifications in the electronic structures and absorption spectra are noticed. Conversely, the boron nitride nanotube-calcium silicate hydrate composite displays an electron-shared type of interaction. The electronic structure and optical absorption spectra of the diamond nanothread and boron nitride nanotube in all configurations studied in the aforementioned composite systems are well maintained. Our findings offer an electronic-level perspective into the bonding characteristics and electronic-optical properties of diamond nanothread/polymer and boron nitride nanotube/calcium silicate hydrate composites for developing next-generation materials.

Microstructure and Mechanical Properties of Diamond–Ceramic Composites Fabricated via Reactive Spark Plasma Sintering

In order to prepare diamond composites with excellent mechanical properties under non-extreme conditions, in this study, a diamond–ceramic composite was successfully prepared via reactive spark plasma sintering using a diamond–Ti–Si powder mixture as the raw material. The microstructures and mechanical properties of the diamond–ceramic composite sintered at different temperatures were studied. When the sintering temperature was 1500 °C, the diamond–ceramic composite exhibited a volume density of 3.65 g/cm3, whereas the bending strength and fracture toughness were high at 366 MPa and 6.17 MPa·m1/2, respectively. In addition, variable-temperature sintering activated the chemical reaction at a higher temperature, whereas lowering the temperature prevented excessive graphitisation, which is conducive to optimising the microstructure and mechanical properties of the composite.

Effect of boron doping levels on the piezoresistive properties of boron-doped diamond films prepared by HFCVD

The exceptional piezoresistive properties of boron-doped diamond (BDD) films render them highly promising for pressure sensor applications. These properties are closely associated with the doping concentration, crystal structure, and substrate material. In this study, BDD films with varying boron concentrations (B/C=500-8000 ppm) were fabricated on silicon and diamond substrates using hot-filament chemical vapor deposition (HFCVD) equipment. The relationship between surface grain characteristics, grain boundaries, and gauge factor (GF) of BDD films deposited on different substrates was systematically examined. The concentration of boron doping significantly influenced the surface morphology, electrical resistivity, and GF of the BDD films. The grain size of BDD films initially increased as the boron doping concentration was raised from 500 ppm to 2000 ppm; however, it subsequently decreased when the boron doping content exceeded 2000 ppm. Moreover, we found that the piezoresistive impact of a BDD film is strongly correlated to its grain size; larger grain sizes result in higher GF values. Notably, compared to those on silicon substrates, the BDD films deposited on diamond substrates exhibited superior piezoresistive characteristics. Specifically at a doping concentration of 2000 ppm, a GF as high as 284 was achieved for the BDD film on a diamond substrate compared to only 140 for that on a silicon substrate.

Pentagonal Symmetry in Aperiodic Cyclic Multiply Twinned Nano- and Mesodiamonds.

This Review provides the first comprehensive overview of the structure and properties of exotic sp3-crystalline aperiodic cyclic multiply twinned nano- (10-100 nm) and meso- (up to 1 mm) diamond particles (MTPs) exhibiting pentagonal symmetry. It spans their independent experimental discoveries (1963, 1964, 1972, and 1983) and theoretical structural insights (1993) to recent advancements. The Review focuses on high-symmetry MTPs formed by the fusion of multiple cubic diamond fragments through [111] facets. The sp3 diamond lattice of individual fragments offers a vast range of MTP varieties. These particles are shown to be a special case of aperiodic crystalline solids with limited dimensions and rotational symmetry, leading to a breakdown of translational invariance. Detailed mathematical analysis of the MTPs' lattices highlights the crucial role of central cores in determining the symmetry and effective dimensions of these structures. Both structural and kinetic aspects of the formation mechanisms of pentagonal diamond particles are considered, revealing the main role of embryo seeds (low fullerenes, polyhexacyclo[5.5.1.12,6.18,12.03,11.05,9]pentadecane (C15), and polyheptacyclo[5.5.1.12,7.19,14.03,13.06,11]octadecane (C18)) in determining the MTPs' symmetry and structure. The effective dimensions of multiply twinned diamonds are shown to be limited by structural stress caused by the mismatch of perfect pentagonal and tetrahedral dihedral angles. The extraordinary mechanical and electronic properties of multiply twinned diamonds are discussed, highlighting that hexagonal interfaces between cubic diamond fragments may determine exceptional ultrahard and quantum characteristics. The MTP X-ray diffraction spectra reveal clear pentagonal patterns with single (diamond decahedrons or dodecahedrons) or ten (diamond icosahedra) central 5-fold axes. A comparative analysis of experimental structural data and simulations at different theoretical levels demonstrates a perfect correspondence of theoretical models with crystalline lattices.

Investigating the broom-like inclusions in type Ib diamond single crystal synthesized by high pressure high temperature

The exceptional properties of diamonds enable diverse applications. However, the applications are significantly hindered by its inclusions. In this study, a specific type of inclusion, broom-like inclusions, has been investigated. The broom-like inclusions in diamonds were synthesized through various high-pressure high-temperature (HPHT) experiments. The synthesis methods were optimized by adjusting the metal catalyst composition, synthesis temperature, Mg(OH)2 content, and nitrogen getter (Ti). The broom-like inclusion morphology and composition were physically characterized and analyzed using various methods. Optical microscopy and SEM were utilized to characterize the morphology and shape of the inclusions, while Raman spectroscopy and Fourier Transform Infrared Spectroscopy were employed to analyze the influence of the defects on the properties of diamonds and investigate the composition of the broom-like inclusions. Gaseous inclusions emerged as crucial for broom-like inclusion formation. They probably originated from residual gases like H2 and CH4. The investigation of broom-like inclusions within diamond crystals has led to the development of various synthetic methods for producing inclusion-free crystals. The findings of this study offer valuable insights into the nature and origin of these inclusions in diamonds, as well as provide strategies to mitigate their formation during production.

Accurate comparison of the fracture toughness of ultra-thick polycrystalline diamond plates by ISO standard method

Due to the difficulty in preparing ultra thick diamonds, current research on the mechanical properties of diamonds mostly focuses on thin samples, which cannot represent the true mechanical properties. In this study, DC arc plasma jet chemical vapour deposition method was used to deposit ultra-thick diamond plate measuring Ø125 mm × 6.5 mm. The size of 18 mm × 4 mm × 3 mm sample were prepared. The samples with dimensions of 18 mm × 4 mm × 3 mm were prepared. For the first time, fracture toughness test samples meeting the ISO 15732 requirements were prepared by using the single-sided beam pre-crack method. The accurate fracture toughness of ultra-thick diamond with pre-crack was obtained using the three-point bending method, 6.5 MPa·m1/2. Samples with sharp or blunt notch by laser cutting were used for comparison. The sharp notch sample had a value similar to that of the pre-crack sample, 6.3 MPa·m1/2. The value of the blunt notch sample was relatively large, 7.5 MPa·m1/2. The effects of defects and grain size on fracture toughness and the reasons for the differences in test results for different notches were analyzed. Overall, obtaining accurate fracture toughness values of ultra-thick diamond by ISO standard is crucial for industrial applications.

Low temperature preparation of the monolayer-graphene/diamond heterostructure with superior mechanical properties

There is increasing interest in the preparation of graphene-on-diamond (GOD) hybrids since it is expected to reveal a new horizon of mechanical applications if the beneficial properties of diamond and graphene are effectively combined. Herein, we demonstrated the atomistic scale events leading to the growth of graphene domains on the diamond during the annealing of the nickel catalyst and diamond substrate by combining experiments and theoretical calculations, including the mechanism transition from high-to low-temperature. Concurrently, the high-quality heterostructure of monolayer graphene on diamond was prepared at a low temperature (760 °C) by rapid thermal annealing technique under the guidance of theoretical insights, and an extraordinarily low coefficient of friction (0.021) was exhibited, representing a 91.1 % reduction against the pristine diamond. The adhesion tests confirmed that such an excellent self-lubricity benefited from the adhesion shield effect of as-grown graphene and the consequent reduction in adhesion energy. Furthermore, the corresponding hardness and elastic modulus were also improved by 14.1 % and 32.5 %, respectively. This investigation presents a great potential of the preparation/integration and application of the GOD heterostructure.

Ultrathin Boron Growth onto Nanodiamond Surfaces via Electrophilic Boron Precursors.

Diamond as a templating substrate is largely unexplored, and the unique properties of diamond, including its large bandgap, thermal conductance, and lack of cytotoxicity, makes it versatile in emergent technologies in medicine and quantum sensing. Surface termination of an inert diamond substrate and its chemical reactivity are key in generating new bonds for nucleation and growth of an overlayer material. Oxidized high-pressure high temperature (HPHT) nanodiamonds (NDs) are largely terminated by alcohols that act as nucleophiles to initiate covalent bond formation when an electrophilic reactant is available. In this work, we demonstrate a templated synthesis of ultrathin boron on ND surfaces using trigonal boron compounds. Boron trichloride (BCl3), boron tribromide (BBr3), and borane (BH3) were found to react with ND substrates at room temperature in inert conditions. BBr3 and BCl3 were highly reactive with the diamond surface, and sheet-like structures were produced and verified with electron microscopy. Surface-sensitive spectroscopies were used to probe the molecular and atomic structure of the ND constructs' surface, and quantification showed the boron shell was less than 1 nm thick after 1-24 h reactions. Observation of the reaction supports a self-terminating mechanism, similar to atomic layer deposition growth, and is likely due to the quenching of alcohols on the diamond surface. X-ray absorption spectroscopy revealed that boron-termination generated midgap electronic states that were originally predicted by density functional theory (DFT) several years ago. DFT also predicted a negative electron surface, which has yet to be confirmed experimentally here. The boron-diamond nanostructures were found to aggregate in dichloromethane and were dispersed in various solvents and characterized with dynamic light scattering for future cell imaging or cancer therapy applications using boron neutron capture therapy (BNCT). The unique templating mechanism based on nucleophilic alcohols and electrophilic trigonal precursors allows for covalent bond formation and will be of interest to researchers using diamond for quantum sensing, additive manufacturing, BNCT, and potentially as an electron emitter.

Spectral and microstructural analysis of the effect of the Ga+ implantation on diamond: a CL-EELS study

Due to its capacity to achieve nanometre-scale machining and lithography, a focused ion beam (FIB) is an extended tool for semiconductor device fabrication and development, in particular, for diamond-based devices. However, some technological steps are still not fully optimized for its use. Indeed, ion implantation seems to affect the crystalline structure and electrical properties of diamond. For this study, a boron-doped ([B] ∼ 1017 atoms·cm−3) diamond layer grown by chemical vapour deposition was irradiated using Ga+ by FIB, with 1 nA current and 5, 20, and 30 keV of acceleration voltage. The Ga+ implanted diamond layer has been analysed through cathodoluminescence (CL) and scanning transmission electron microscopy (STEM)-related techniques. The beam penetration depth has been simulated by Monte Carlo calculations of both Ga+ (FIB) and e− (CL) beams at different energies. The comparative CL analysis of the layer as-grown and after implantation revealed peaks related to defects, such as A band, H3 centre, and defects present in the green band region. The STEM studies for the 30 keV implanted sample showed that the diamond lattice is affected by the damage, evidencing amorphisation in the layer with a sp2/sp3 ratio of 1.37, estimated by electron energy loss spectroscopy. Therefore, this study highlights the effects of the Ga+ implantation on the optical and structural characteristics of diamond, using different methods.

Light B Doping by Ion Implantation into High‐Purity Heteroepitaxial Diamond

The low‐concentration boron doping is performed from 1016 to 1018 cm−3 by ion implantation into heteroepitaxially synthesized large‐area diamond and electrical properties are investigated. Photoluminescence analysis is first carried out to clarify the optical properties of the heteroepitaxial diamond substrate. As a result, defect complexes of nitrogen‐vacancy and silicon‐vacancy are hardly detected in this substrate, suggesting that optically high‐purity diamond can be accomplished by heteroepitaxial growth. Then, the electrical properties of resistivity, mobility, carrier concentration, and conductive type by Hall effect measurements are investigated. For the samples with doping concentrations higher than 1016 cm−3, the electrical activation of implanted B acting as acceptors is confirmed. The compensation ratio for the sample with 3.5 × 1017 cm−3 concentration reaches 76%, indicating the presence of compensating donor‐like centers. With increasing the doping concentration to 3.5 × 1018 cm−3, the compensation ratio is significantly reduced to 35%. The observed mobility of the higher doped sample takes almost the ideal value observed for the sample doped by chemical vapor deposition process. It is suggested that the heteroepitaxial synthesis of large‐area and high‐purity substrates should contribute to the further development of the application to electronic, optical, and sensing devices in the future.

Multifunctional diamond‐based catalysts: Promising candidates for energy conversions in extreme environments—A mini‐review

AbstractIn order to properly utilize the abundant CO2 and water resources, various catalytic materials have been developed to convert them into valuable chemicals as renewable fuels electrochemically or photochemically. Currently, most studies are conducted under mild laboratory conditions, but for some extreme environments, such as Mars and space stations, there is an urgent need to develop new catalysts satisfying such special requirements. Conventional catalytic materials mainly focus on metals and narrow bandgap semiconductor materials, while the research on wide and ultrawide bandgap materials that can inherently withstand extreme conditions has not received enough attention. Given the robust stability and excellent physico‐chemical properties of diamond, it can be expected to perform in harsh environments for electrocatalysis or photocatalysis that has not been investigated thoroughly. Here, this review summarizes the catalytic functionality of diamond‐based electrodes with various but tunable product selectivity to obtain the varied C1 or C2+ products, and discusses some important factors playing a key role in manipulating the catalytic activity. Moreover, the unique solvation electron effect of diamond gives it a significant advantage in photocatalytic conversions which is also summarized in this mini‐review. In the end, prospects are made for the application of diamond‐based catalysts under various extreme conditions. The challenges that may be faced in practical applications are also summarized and future breakthrough directions are proposed at the end.

Target Detection of Diamond Nanostructures Based on Improved YOLOv8 Modeling.

Boron-doped diamond thin films exhibit extensive applications in chemical sensing, in which the performance could be further enhanced by nano-structuring of the surfaces. In order to discover the relationship between diamond nanostructures and properties, this paper is dedicated to deep learning target detection methods. However, great challenges, such as noise, unclear target boundaries, and mutual occlusion between targets, are inevitable during the target detection of nanostructures. To tackle these challenges, DWS-YOLOv8 (DCN + WIoU + SA + YOLOv8n) is introduced to optimize the YOLOv8n model for the detection of diamond nanostructures. A deformable convolutional C2f (DCN_C2f) module is integrated into the backbone network, as is a shuffling attention (SA) mechanism, for adaptively tuning the perceptual field of the network and reducing the effect of noise. Finally, Wise-IoU (WIoU)v3 is utilized as a bounding box regression loss to enhance the model's ability to localize diamond nanostructures. Compared to YOLOv8n, a 9.4% higher detection accuracy is achieved for the present model with reduced computational complexity. Additionally, the enhancement of precision (P), recall (R), mAP@0.5, and mAP@0.5:0.95 is demonstrated, which validates the effectiveness of the present DWS-YOLOv8 method. These methods provide effective support for the subsequent understanding and customization of the properties of surface nanostructures.

Fast, Efficient Tailoring Growth of Nanocrystalline Diamond Films by Fine-Tuning of Gas-Phase Composition Using Microwave Plasma Chemical Vapor Deposition.

Nanocrystalline diamond (NCD) films are attractive for many applications due to their smooth surfaces while holding the properties of diamond. However, their growth rate is generally low using common Ar/CH4 with or without H2 chemistry and strongly dependent on the overall growth conditions using microwave plasma chemical vapor deposition (MPCVD). In this work, incorporating a small amount of N2 and O2 additives into CH4/H2 chemistry offered a much higher growth rate of NCD films, which is promising for some applications. Several novel series of experiments were designed and conducted to tailor the growth features of NCD films by fine-tuning of the gas-phase compositions with different amounts of nitrogen and oxygen addition into CH4/H2 gas mixtures. The influence of growth parameters, such as the absolute amount and their relative ratios of O2 and N2 additives; substrate temperature, which was adjusted by two ways and inferred by simulation; and microwave power on NCD formation, was investigated. Short and long deposition runs were carried out to study surface structural evolution with time under identical growth conditions. The morphology, crystalline and optical quality, orientation, and texture of the NCD samples were characterized and analyzed. A variety of NCD films of high average growth rates ranging from 2.1 μm/h up to 6.7 μm/h were successfully achieved by slightly adjusting the O2/CH4 amounts from 6.25% to 18.75%, while that of N2 was kept constant. The results clearly show that the beneficial use of fine-tuning of gas-phase compositions offers a simple and effective way to tailor the growth characteristics and physical properties of NCD films for optimizing the growth conditions to envisage some specific applications.

Improving Trace Detection of Methylene Blue by Designing Nanowire Array on Boron-Doped Diamond as Electrochemical Electrode

In this study, a boron-doped diamond nanowire array (BDD-NWA)-based electrode is prepared by using a microwave plasma chemical vapor deposition system and treated with inductively coupled plasma reactive ion etching. The BDD-NWA electrode is used for trace detection of methylene blue, which has a wide linear range of 0.04–10 μM and a low detection limit of 0.72 nM. Both the superhydrophilicity (contact angle ~0°) and the dense nanowire array’s structure after the etching process improve the sensitivity of the electrochemical detection compared to the pristine BDD. In addition, the electrode shows great repeatability (peak current fluctuation range of −3.3% to 2.9% for five detection/cleaning cycles) and stability (peak current fluctuation range of −5.3% to 6.3% after boiling) due to the unique properties of diamonds (mechanical and chemical stability). Moreover, the BDD-NWA electrode achieves satisfactory recoveries (93.8%–107.5%) and real-time monitoring in tap water.

Improving frictional state at fretting interfaces through the covalent structure of diamond–graphite–graphene

This study proposes a novel approach based on the covalent structure of diamond–graphite–graphene (CDGG) to integrate the outstanding properties of diamond, graphite, and graphene, synergistically improving frictional behavior of fretting interfaces. The results demonstrated that in-situ CDGG significantly reduced the alternating stress at the contact interface, the friction coefficient decreased by 40–62 % over pristine diamond coatings under gross slip regime, accompanied by a shorter running-in period. The counterpart pair wear corresponding to in-situ CDGG was lower, and no delamination caused by metal adhesion. The surface graphene/graphite exhibited good frictional toughness, effectively absorbing the relative displacement at contact interface, enabling CDGG to exhibit partial slip regime under higher loads and smaller displacement amplitudes.

Low-Cost Preparation of Diamond Nanopillar Arrays Based on Polystyrene Spheres.

Diamond nanopillar arrays can enhance the fluorescence collection of diamond color centers, playing a crucial role in quantum communication and quantum sensing. In this paper, the preparation of diamond nanopillar arrays was realized by the processes of polystyrene (PS) sphere array film preparation, PS sphere etching shrinkage control, tilted magnetron sputtering of copper film, and oxygen plasma etching. Closely aligned PS sphere array films were prepared on the diamond surface by the gas-liquid interfacial method, and the effects of ethanol and dodecamethylacrylic acid solutions on the formation of the array films were discussed. Controllable reduction of PS sphere diameter is realized by the oxygen plasma etching process, and the changes of the PS sphere array film under the influence of etching power, bias power, and etching time are discussed. Copper antietching films were prepared at the top of arrayed PS spheres by the tilted magnetron sputtering method, and the antietching effect of copper films with different thicknesses was explored. Diamond nanopillar arrays were prepared by oxygen plasma etching, and the effects of etching under different process parameters were discussed. The prepared diamond nanopillars were in hexagonal close-rowed arrays with a spacing of 800 nm and an average diameter of 404 nm, and the spacing, diameter, and height could be parametrically regulated. Raman spectroscopy and photoluminescence spectroscopy detection revealed that the prepared diamond nanopillar array still maintains polycrystalline diamond properties, with only a small amount of the graphite phase appearing. Moreover, the prepared diamond nanopillar array can enhance the photoluminescence of diamond color centers by approximately 2 times. The fabrication method of diamond nanopillar array structures described in this article lays the foundation for quantum sensing technology based on diamond nanostructures.

Strained diamond for quantum sensing applications

Apart from being an extraordinary optical and electronic material, diamond has also found applications in quantum mechanics especially in quantum sensing with the discovery and research development of various color centers. Elastic strain engineering (ESE), as a powerful modulation method, can tune the quantum properties and improve the performance of diamond quantum sensors. In recent years, deep ESE (DESE, when >5% elastic strain, or >σ ideal/2 is achieved) has been realized in micro/nano-fabricated diamond and shows a great potential for tuning the quantum mechanical properties of diamond substantially. In this perspective, we briefly review the quantum properties of diamond and some of the corresponding sensing applications carried out with ESE, and look at how DESE could be applied for further tuning the quantum sensing properties of diamond with desired applications and what the critical challenges are.

Diamond-Like Carbon (DLC) Coatings : Classification, Properties, and Applications

This paper presents the most recent and important research trends on the friction and wear properties of diamond like carbon (DLC) coatings deposited on different types of materials. For this the invention, methods, techniques, and design related to this area are discussed. The different trends of tribological properties of materials under different operating conditions are observed. In this article, an attempt is made to provide an opportunity for the future researchers to identify the recent trend of these areas. It is expected that the applications of these results will contribute to the improvement of different concerned mechanical processes. This review article also includes some patents relevant to the method of producing a DLC film.