We report an ambient-pressure liquid-metal-assisted CVD strategy that enables shape-programmable growth of microscale diamond by coupling a liquid-metal Ga-In with ferrocene (Fe(C5H5)2) as a carbon precursor, nanodiamond seeds, and nanosilicon. Building on liquid-metal diamond synthesis, this approach pushes liquid-metal growth toward lower temperature (900°C, 1 atm) while enabling single-crystal diamonds to scale from ∼10µm to several tens of micrometers with well-developed faceting. Ferrocene decomposition supplies a sustained interfacial carbon flux captured and redistributed by the Ga-In melt toward seed-rich liquid-solid interfaces. Defect-rich nanodiamond provides the crystallographic template required for reliable sp3 nucleation despite low carbon solubility in Ga-In. Nanosilicon plays a complementary role by tuning interfacial kinetics and facet competition, enabling control of crystal habit: cubic (∼10µm), truncated-tetrahedral, and fully faceted octahedral diamonds are obtained by adjusting the nanosilicon: nanodiamond ratio, with octahedral crystals reaching ∼50µm. Crystal size is further scaled by regulating hydrogen flow: lowering the H2 rate increases carbon retention at the liquid-metal interface, raises supersaturation, and accelerates diamond deposition. Together, habit control and size scaling establish a practical route for facet regulation and size control under ambient pressure, offering tunable microscale single-crystal diamonds under mild conditions.

200 keV energy electron irradiation of single-crystal diamond: Quantification of vacancy and nitrogen-vacancy production

Wide-bandgap materials are central to next-generation high-power, radio-frequency, and quantum technologies, yet their performance is often limited by crystalline defects such as dislocations. Single-crystal diamond in particular exhibits exceptional electronic and thermal properties, however, accurately and scalably quantifying defect density remains challenging. Here, we present an integrated methodology for characterizing dislocation densities in diamond using high-resolution X-ray diffraction and validate it using complementary Raman spectroscopy, hydrogen etch-pit analysis, and Hall effect measurements. Central to this approach is a custom Python-based tool that processes X-ray rocking curves and reciprocal space maps. The framework is applied to four commercially available grades of diamond substrates, spanning a wide defect density range (∼105 to 108 cm-2). Consistent trends are observed across all characterization techniques, with electronic-grade diamond exhibiting the highest crystalline quality and lowest defect density. Application of the analysis tool to GaN samples further demonstrates its adaptability to other wide-bandgap material systems. Overall, this work establishes a robust, scalable, and versatile platform for high-throughput defect analysis in diamond and related wide-bandgap semiconductors.

Single-crystal diamond (SCD) has excellent mechanical, thermal and physical properties that rank among the highest of all substances. It has widespread applications in diverse fields such as cutting tools, optical windows, spintronics and power electronics. However, SCD is difficult to machine via mechanical processes due to its extremely high hardness. In recent years, laser processing has attracted attention since it enables non-contact efficient machining regardless of material hardness. In this study, femtosecond pulsed laser, which is considered to be capable of high-precision machining with low thermal effect, was used for micromachining of SCD, and the effects of laser irradiation parameters on the surface texture, roughness and profile geometry, as well as subsurface material structural changes, were investigated. It was found that even under femtosecond pulses thermal effect existed and that using a higher laser scanning speed was helpful to eliminate thermal cracks formation. The laser machined surfaces were covered with nanoscale periodical surface ripples with a surface roughness in the level of 0.10 μm Ra. Raman analysis of the SCD surface after laser machining showed that amorphous carbon and nanocrystalline graphite existed as a composite material. The graphitization depended on the laser fluence and hatching width and was particularly pronounced at low fluence and small hatching width. It was also demonstrated that acid cleaning could remove most of the graphite layer and reduce surface roughness. As samples, a few three-dimensional micro cavities with flat bottoms and sharp corners were created. This study demonstrates that femtosecond pulsed laser is a suitable method for machining micro three-dimensional shapes in SCD while it is important to optimize the laser machining conditions to avoid thermal damage and improve the surface quality. • Femtosecond pulsed laser micromachining characteristics of single-crystal diamond were investigated. • By increasing laser scanning speed, crack generation due to thermal effect was suppressed. • Flat surfaces with surface roughness of 0.10 μm Ra were successfully obtained under suitable conditions. • A laser-machined surface was covered with a layer of amorphous carbon and nanocrystalline graphite. • The graphite layer thickness and surface roughness depended on the overlap of the laser beam wings.

Material removal mechanism in femtosecond laser-microstructured natural single-crystal diamond cutting tools by finite element simulation and experimentation

The heteroepitaxial growth of large-area thick single-crystal diamond is strongly limited by stress accumulation and crack formation during prolonged deposition. Laser-patterned templates have been demonstrated as an effective approach for obtaining crack-free free­standing diamond layers. In this work, the influence of laser grooves on the growth behavior of diamond films grown on Ir/YSZ/Si (001) substrates by microwave plasma chemical vapor deposition (MPCVD) is systematically investigated. Laser grooves introduced into a thin diamond seed layer generate a spatially non-uniform growth template. During the early growth stage, polycrystalline diamond forms inside the grooves, whereas the surrounding regions maintain stable (001)-oriented epitaxial growth. As deposition proceeds, the faster vertical growth of single-crystal diamond progressively overgrows the groove regions, leading to gradual groove filling and closure, ultimately forming a laterally continuous epitaxial diamond film. The buried grooves with polycrystalline diamond act as mechanically compliant zones that facilitate stress redistribution during thick-film growth, thereby suppressing crack formation and enabling the fabrication of millimeter-scale freestanding diamond layers with high crystalline quality. This work clarifies how laser-patterned templates regulate growth evolution and stress accom­modation during diamond heteroepitaxy, providing insights for the controlled growth of large-area thick single-crystal diamond films on highly mismatched substrates.

Chemical bonding evolution of near-surface nitrogen and defects in ultra-low-energy nitrogen implanted (100) single crystal diamond probed by synchrotron x-ray spectroscopies

Abstract In this study, the effects of feed and tool rake angle on surface pit formation and arithmetic mean roughness Sa of a TATB-based PBX simulant were systematically investigated through theoretical modelling, ultra-precision cutting experiments, and surface topography measurements. A feed-induced indentation fracture model for TATB particles was developed based on indentation fracture theory and contact mechanics to quantitatively predict the key characteristic parameters of surface pit formation. On this basis, a comprehensive predictive model for the arithmetic mean roughness Sa was established by integrating the surface pit component predicted by the above fracture model with the matrix residual profile component and the component associated with other influencing factors. Ultra-precision cutting experiments were performed using single-crystal diamond tools with different rake angles at feeds ranging from 1 µm/r to 16 µm/r, and surface topographies were measured using white light interferometry. The results indicated that surface pit depth increased monotonically with feed and stabilised at higher feed values, in agreement with theoretical predictions. The tool rake angle primarily influenced Sa by controlling plastic side flow in the matrix, with the −15° rake angle tool yielding optimal cutting performance. The predicted Sa values showed good agreement with experimental measurements, with an average relative error of approximately 5.42%, confirming the validity and reliability of the proposed models and providing a theoretical basis for process parameter optimisation in the ultra-precision cutting of TATB-based PBX materials.

Molecular dynamics simulations were performed to investigate the nanometric cutting of polycrystalline oxygen-free copper using a single-crystal diamond tool. The effects of grain size, tool geometry (rake angle and edge radius), cutting speed, and ambient temperature on atomic migration, dislocation activity, and tool wear were systematically analyzed. The results indicate that material removal is dominated by cutting-induced amorphization and the formation of hcp-coordinated defect structures, while dislocation activity governs plastic deformation and cutting force fluctuations. A damaged subsurface layer, composed of amorphous structures, hcp-coordinated defects, and residual dislocations, is formed beneath the machined surface. Increasing grain size reduces grain-boundary-induced stress concentration and suppresses subsurface damage. A larger rake angle facilitates chip removal and reduces damage, whereas a larger edge radius intensifies dislocation activity and amorphization. Higher cutting speeds reduce lattice distortion and subsurface damage but increase stress concentration on the tool. Elevated temperature enhances atomic mobility, promoting amorphization and subsurface deformation while accelerating tool wear. These findings provide insight into the nanometric cutting behavior of polycrystalline copper and offer guidance for optimizing process parameters to improve surface integrity and tool life.

Single-crystal diamond has attracted much attention because of its wide bandgap and specific thermal and optical properties, which is suitable for the utilization on integrated photonic devices and power semiconductor devices. However, its extremely high hardness confines the processing ability of micro/nano structures, which is the main determinant of devices performance. Here, multimode patterning methods using ultrafast laser regulated in spatial-domain with high precision are proposed. Through designing of spatial beam phase, specific patterned micro/nano structures ranging from sub-micrometer scale to millimeter scale can be printed on diamond surface with improved efficiency. This provides a facile strategy for the fabrication of programmable patterns with sub-wavelength resolutions. The laser ablation and graphitization result can be precisely predicted by calculating free electron density and validated through patterning experiment. A diamond holographic element is designed and fabricated through the proposed method, which can project the reconstructed holographic image for display applications. This work presents a promising method for preparing of single-crystal diamond-based next-generation semiconductor devices and integrated photonic systems requiring precise light field control.

Investigation of etch pit filling during single crystal diamond growth using 3D geometric growth model

HTHP-induced color transition and NV center engineering in MPCVD single-crystal diamond: Defect mechanism and quantum-mechanical property synergy

Single-crystal diamond, as a substrate material of radiation detector for radiotherapy, has attracted growing attention because of its tissue equivalence and high radiation resistance. X-ray detectors were fabricated from single-crystal diamond with high nitrogen impurity content (N∼1017 atoms/cm−3) and low nitrogen impurity content (N∼1016 atoms/cm−3). Raman spectroscopy, photoluminescence spectroscopy (PL), and electron paramagnetic resonance spectra were used to characterize the change in defects of the three states, such as substrate, after metallization and after x-ray irradiation. The results indicate that the defects containing nitrogen change after x-ray irradiated diamond with high N content. Hence, detectors based on diamond with low N content exhibit less than 0.5% both the uncertainty of repeatability and nonlinearity, while detectors based on diamond with high N content exhibit more than 1% because of the change in NV− and NV0 centers. Boron doping was employed to compensate the defects as a secondary treatment. The results indicate that detectors based on boron-compensated diamond exhibit both the uncertainty in the repeatability and nonlinearity between 0.5% and 1%. This provides a new approach for low-cost fabrication of x-ray detectors.

applicability is largely because of the exceptional physical properties of diamonds, including their extreme hardness, high thermal conductivity, and excellent electrical insulation properties. Precise and efficient processing methods are essential for widespread industrial applications. However, because of the extreme hardness of diamonds, achieving precise processing remains a challenge. Diamond processing techniques can be broadly classified into contact and non-contact methods. Contact methods include mechanical polishing [7], chemical mechanical polishing [8], and dynamic friction polishing [9, 10] . These approaches involve physical contact and rely on mechanical, chemical, and/or thermal processes to remove materials. Contact methods, which are traditional and widely

Heteroepitaxial growth of (100) single-crystal diamond with reduced wafer bow via SiO₂ Nanospheres interlayer

Research on single-crystal diamond surface polishing process and material removal mechanism based on inductively coupled plasma etching reactions

The inhomogeneous distribution of P1 centers in type 1b HPHT diamond samples allows multiple DNP mechanisms to occur within the same crystal, resulting in complex DNP spectra. At some crystal orientations, different DNP mechanisms can compete to drive hyperpolarization with different signs at the same applied microwave frequency. We perform microwave-irradiated DNP using both monochromatic and frequency-modulated microwave excitation to explore the competition between these DNP mechanisms in diamond at room temperature. We show that frequency-modulated DNP is a tool for suppressing certain DNP mechanisms while enhancing others in a single-crystal diamond sample. Frequency modulation also enables higher enhancement of the NMR signal beyond traditional monochromatic DNP under some conditions. In a powder sample, competing enhancement mechanisms can also arise from different crystallite orientations. At certain microwave frequencies, we observe that the DNP signal changes sign during the polarization build-up, even with monochromatic microwave irradiation. We do not observe this phenomenon in any single-crystal spectrum. We discuss both methods of selectively enhancing the different DNP mechanisms that drive 13C NMR signal enhancement.

Ultrathin single-crystal diamond (SCD) resonators offer exceptional potential for high-performance nanoelectromechanical systems (NEMS), but achieving sub-100nm thickness with low dissipation remains a major fabrication challenge. In this work, we develop a smart-cut-assisted thinning strategy to reliably fabricate SCD cantilevers with thicknesses down to ~50nm, representing the thinnest SCD NEMS cantilever achieved to date. Operating from 10kHz to 3MHz, these devices exhibit high-quality factors (∼5 × 104 at room temperature and ∼6 × 103 at 773 K). The resulting ultrathin resonators exhibit controllable geometries with resonance frequencies that closely follow the Euler-Bernoulli beam model, confirming high structural integrity. The cantilevers demonstrate robust thermal stability, with a low temperature coefficient of frequency of -10ppm/K. As a result, the ultrathin diamond cantilevers yield a force sensitivity of ∼10-17 N/Hz1/2 and a mass resolution of ∼5.89 × 10-20kg, close to that of a carbon nanotube cantilever. This work establishes the strategy for batch fabrication of ultrathin SCD NEMS resonators as a highly promising platform for next-generation high-sensitivity and robust nanomechanical sensing.

Diamond photonic crystal cavities offer exceptional properties for interfacing color centers in diamond to integrated photonic circuits. Leveraging Purcell enhancement of the color centers' emission into the zero-phonon line, the development of high quality, low mode volume single-crystal diamond resonators remains one of the key challenges for building diamond quantum networks. In this paper, we present both a robust, versatile photonic crystal design as well as a scalable fabrication process realizing suspended nanobeam cavities. Measurements of confocal microscopy with broadband excitation yield quality factors of more than 5000. We further demonstrate a fast and facile characterization of our structures based on confocal photoluminescence imaging. This method not only provides a more detailed look at the higher order modes within diamond nanobeam resonators but also serves as a non-destructive diagnostic of the modes' susceptibility to fabrication imperfections, providing critical feedback for scalable, high-yield integrated quantum photonic device development.

This Letter reports on a vertical, bulk-conducting photoconductive semiconductor switch (PCSS) fabricated on an intrinsic Type IIa single-crystal diamond substrate. Under near-bandgap excitation at 225 nm with a 20 μJ pulse, a strong photocurrent response of 17.1 A at 1 kV DC bias magnitude is obtained by (i) tuning the optical trigger wavelength to the “matched-absorption” window (224–235 nm) near the band edge, where the optical penetration depth becomes comparable to the 500 μm substrate thickness, and (ii) choosing the bias polarity ensuring electron-dominant conduction, given that electrons have a higher mobility than holes in diamond. The PCSS has an area-normalized responsivity of 54.2 mA W−1 cm−2 and an effective on-resistance of 8.48 Ω, with a fast 90%–10% transient fall time of 25 ns, attributed to carrier sweep-out. These results support vertical, bulk-conducting intrinsic diamond PCSS as a promising platform for high-power optical switching and provide new insight into intrinsic photoconductivity in diamond.