​Graphene/diamond heterostructures have attracted much attention by combining the high carrier mobility of graphene with the high phonon frequency of diamond. In this study, in situ graphene/diamond heterostructures were fabricated on single-crystal diamond (100) substrate using a nickel (Ni)-catalyzed high-temperature annealing method. The influence of Ni catalyst thickness (10-100 nm) on the number of graphene layers, surface morphology, and electrical properties was systematically investigated using Raman spectroscopy and conductive atomic force microscopy. Temperature-dependent electrical transport measurements from 2 to 400 K revealed an anomalous sharp drop in resistance to negative values near 100 K for the fabricated heterostructures, suggesting a possible signature of high-temperature superconductivity. High-resolution transmission electron microscopy (HRTEM) analysis further revealed the presence of an sp²-sp³ hybridized transition layer approximately 2 nm thick at the graphene/diamond interface. The unique bonding configuration and electronic structure of this interfacial region are likely key to inducing unconventional superconducting states, which warrants further verification by more rigorous transport and magnetic measurements.

Direct current (DC) arc plasma jet chemical vapor deposition (CVD) has emerged as an important technique for synthesizing high-quality diamond. Nevertheless, the central challenge of this technique stems from the interfacial mismatch between diamond and the substrate, which hinders the scalable synthesis of crack-free, high-quality diamond films. Here, we optimize the performance of the graphite substrate by sequentially depositing titanium (Ti) and molybdenum (Mo) layers via interfacial engineering. The Mo layer effectively resists erosion from energetic hydrogen (H) species in the DC arc plasma and promotes diamond nucleation. Simultaneously, Ti enhances adhesion at the graphite-Mo interface to improve resistance against stress during diamond deposition. Post-growth, Ti facilitates stress-induced interface fracture, allowing diamond films to self-separation. The Mo-Ti-Graphite (MTG) substrate enables the scaled production of large-area (5-inch), high-quality diamond films, achieving an impressive crack-free yield of similar to 80%. Systematic experimental and theoretical analyses reveal that the MTG substrate enhances diamond quality and elucidate the mechanism of self-separation. Consequently, this approach offers an effective route to the cost-effective, scalable fabrication of high-quality, crack-free diamond films.

This study employs microwave plasma chemical vapor deposition (MPCVD) to systematically investigate the synergistic effects of deposition temperature (793-925 °C) and methane concentration (0.5-2.0%) on the homoepitaxial growth of (111)-oriented single-crystal diamond. Through comprehensive characterization, the intrinsic relationships between process parameters and crystal surface morphology, crystalline quality, and internal stress were revealed. Results indicate that the growth rate increases significantly with rising temperature and methane concentration, reaching a maximum of 1.73 µm h-1. Under low temperature and low methane conditions, cracks and etch pits along the <110> direction were observed. These morphological features transitioned into wavy and eventually straight step-flow structures as process parameters were optimized, while sharp step structures emerged at high methane concentrations. XRD and Raman analyses demonstrated that samples grown in the medium-temperature range (861-875 °C) exhibited the best crystalline quality and the lowest stress, attributed to a balance between atomic migration capability and stress relaxation, which is crucial for high-quality epitaxial growth. This work provides key process windows and theoretical support for the controlled growth of (111) single-crystal diamond for electronic device applications.

The high-precision machining of polycrystalline diamond (PCD) remains fundamentally constrained by its ultrahigh hardness, exceptional wear resistance and crystallographic orientation anisotropy. This paper presents a synergistic surface engineering strategy of PCD integrating plasma pretreatment with short-duration chemical mechanical polishing (CMP). Morphological analyses revealed the eradication of deep mechanical scratches following plasma irradiation and a short-duration (15 min) of CMP, significantly reducing the average surface roughness Ra from 1.05 nm to 0.30 nm and Sa from 6.11 nm to 1.93 nm. Identical-location characterization confirmed that this global planarization was governed by reducing intergranular height disparities among distinct crystal planes and lowering the intragranular roughness. SF6/O2 plasma irradiation induced the formation of a nanoscale modified layer enriched in C-O, C--O, and C-F functional groups. This localized chemical modification structurally perturbs the diamond lattice, attenuating intrinsic C-C bond strength and facilitating the atomic-scale removal of carbon atoms during the short-duration CMP process. Furthermore, cathodoluminescence spectroscopy verified that the plasma pretreatment combined with short-duration CMP can effectively eliminate subsurface damage, originated from the pristine mechanical polishing. This work provides a novel route for the high-efficiency and high-quality processing of PCD.

Facing growing thermal challenges in electronics, diamond/carbon nanotube (CNT) composites offer a breakthrough heat-dissipation solution, yet the phonon transport across covalently bonded diamond/CNT interfaces remains poorly understood at the atomic scale. Based on our experimental synthesis results, we build the interfacial bonding structure model of the diamond/CNT composite materials for the first time and demonstrate the effects of covalent bonding and atomic interfacial structure on interfacial thermal conductance (ITC). The interfacial chemical bonding can significantly enhance ITC (by 4 to 73 times compared to unbonded interfaces, depending on the temperature and the number of bonds per unit diameter), with the most pronounced enhancement observed at 700 K. Increasing the number of bonds further improves ITC by exciting more delocalized phonons to participate in transport. Structural analysis reveals that the combination of diamond with the (111) crystal plane and zigzag CNTs yields the optimal thermal conductance, while phonon analysis shows that delocalized phonons in CNTs contribute more prominently to thermal transport. We design several diamond/CNT array structures, including aligned and crossed arrangements, and achieve ITC on the order of ∼100 GW/(m2 K), which is the highest value reported in the literature. Our research not only demonstrates a method for fabricating high-performance diamond/CNT composites with excellent heat-dissipation properties, but also paves the way for the design and preparation of novel carbon‑based materials.

The integration of high-thermal-conductivity diamond films onto silicon carbide (SiC) substrates offers a promising pathway for thermal management in high-power electronic devices. Here, we investigate the depth-dependent thermal conductivity of a similar to 5 mu m-thick diamond film grown on SiC by hot filament chemical vapor deposition (HFCVD) using square-pulsed source thermometry. Electron backscatter diffraction and transmission electron microscopy reveal pronounced grain coarsening from the nucleation interface to the film surface. By combining frequency-dependent thermal penetration with a depth-resolved thermal transport model, we quantitatively reconstruct the thermal conductivity profile. The thermal conductivity increases sharply from similar to 60 W m(-1) K-1 near the nucleation region to similar to 200 W m(-1 )K(-1 )at the surface, directly reflecting the underlying microstructural evolution. These results provide a physically grounded understanding of graded heat transport in HFCVD diamond and offer practical guidance for engineering diamond-based thermal management layers for next-generation power devices.

Single crystal diamond shows great potential for electronic devices, but dislocations and other structural defects remain common, severely limiting device performance. Here, we study the evolution of dislocation-related etch pits on (100) monocrystalline diamond surfaces using O/H plasma etching, which preferentially attacks weak chemical bonds around defects. Femtosecond laser marking enables precise relocation of the same microscopic region before and after homoepitaxial growth. By combining sequential atomic force microscopy (AFM) depth profiling with confocal Raman stress imaging, we track the propagation behavior of threading dislocations. Quantitative analysis of etch-pit depth evolution and Raman peak-shift distributions reveals that the stress field associated with a [001] edge dislocation propagates upward from approximately 20 µm below the substrate surface. At a depth of ∼10 µm above the substrate interface, the stress-field distribution exhibits a characteristic branching signature, suggestive of a transition from a single edge-type toward two mixed-type dislocation features. These dislocation trajectories continue into the CVD overgrowth layer. The proposed propagation pathway is a phenomenological model supported by consistent AFM and Raman data; direct crystallographic verification (e.g., TEM) remains for future work. This study demonstrates that the correlative etching-Raman protocol provides complementary insights into the three-dimensional propagation of dislocations in diamond.

The polycrystalline diamond films have attracted considerable attention in the field of thermal management in high-frequency, high-power devices. However, non-uniform plasma distribution during the film fabrication process results in significant variations in film performance, which poses a substantial challenge to their practical application. To this end, the finite element method was employed to conduct a 3D simulation of non-uniform plasma distribution induced by structural anharmonicity in the MPCVD reactor. Research findings indicate that when the resonant cavity experiences geometric misalignments such as deflection or offset, leading to structural anharmonicity, the high power density region of the plasma will shift in a direction opposite to the change in structural resonance. The anharmonicity of the resonant cavity structure, which leads to a non-uniform plasma distribution, can be effectively compensated for by adjusting the structural resonant characteristic. For instance, when the resonant cavity antenna structure is deflected by 2 degrees, the plasma will demonstrate a significant shift. By translating the substrate along the direction of this plasma shift by 3 mm, it can be restored to its central axis position within the resonant cavity. This investigation provides a novel theoretical foundation and technical pathway for the regulation of plasma spatial uniformity.

Single-crystal diamond (SCD) represents an ideal material for optical components, owing to its exceptional physical and chemical properties. Nitrogen doping can enhance SCD growth rate and reduce cost, but degrade optical properties. Solving the problem is critical for expanding applications in optical systems. In this study, microwave plasma chemical vapor deposition (MPCVD) was employed to synthesize nitrogen-doped SCD at 31.71 mu m/h, followed by rapid vacuum annealing via Joule heating. This process improved both processing efficiency and optical performance, significantly increasing transmittance from ultraviolet to mid-infrared. After annealing at 2373 K for 2 min, the transmittance at 10.6 mu m increased from 56.41 % to 69.91 %. The optical enhancement originated from the transformation of nitrogen-related defects within SCD during heat treatment. Substitutional nitrogen (NS) associates with vacancies to form nitrogen-vacancy (NV) centers. NS0 decreased from 12.79 ppm at 1973 K to 2.41 ppm at 2173 K, stabilizing near 2.25 ppm. Other defects, including NVH, N2V-, vacancy clusters, N2VH, hydrogen-modified A-center and hydrogen-related defects, also decreased with higher annealing temperature. These defects decomposed, migrated, or merged at high temperatures, forming more complex nitrogen-related defects. This study addressed optical degradation in high-growth-rate nitrogen-doped SCD and supported industrial application of diamond optical components.

Diamond films prepared by conventional microwave plasma chemical vapor deposition （MPCVD） often face issues such as low growth rates，disordered grain orientations，and non-diamond phase defects，which limit further enhancement of their optical properties. This study introduces CO₂ as an auxiliary gas to deposit high-quality diamond films using the MPCVD method. Diamond film deposition is conducted by introducing different flow rates of CO₂， and the optical emission characteristics of the plasma under varying CO₂ flow rates are measured using optical emission spectroscopy （OES）. The crystallinity quality， grain orientation， surface morphology， and growth rate of the diamond films are characterized by XRD， Raman， and SEM. The results indicate that adding a certain amount of CO₂ （flow ratio of CO₂/CH₄=2/6） is conducive to obtaining diamond films with a high （110） preferred orientation （I₂₂₀/I₁₁₁=18.19）. An excessively high CO₂/CH₄ flow ratio intensifies the etching effect of oxygen-containing groups， reducing the degree of preferential grain orientation. The addition of an appropriate amount of CO₂ significantly improves the crystalline quality of the diamond， with the full width at half maximum （FWHM） of the diamond characteristic peak decreasing from 12.68 cm-1 to 8.26 cm-1. Furthermore， the addition of a suitable amount of CO₂ promotes diamond growth to some extent. Under the optimized flow ratio condition of CO₂/CH₄=2/6， this study successfully prepares a high （110） orientation （I₂₂₀/I₁₁₁=18.19） diamond film with a growth rate of 4 μm/h. After polishing， the self-standing diamond film achieves a transmittance of 71% at the 10.6 μm wavelength. Its transmittance in the long-wave infrared band approaches the theoretical value， meeting the requirements for applications such as long-wave infrared optical windows and extreme ultraviolet lithography machine windows.

Silicon-based manifold microchannel heat sinks (MMHSs) have demonstrated strong heat dissipation capability but show clear performance limitations under extreme heat fluxes. Diamond, with its exceptional thermal conductivity, offers a promising pathway toward managing ultra-high heat fluxes. However, studies on diamondbased MMHSs that integrate manifold architectures for efficient fluid delivery remain relatively limited. Here, we present a fully diamond-based embedded manifold microchannel heat sink (FDMMHS) for ultra-high heat flux thermal management. Two configurations with channel widths of 100 mu m and 50 mu m were fabricated and tested using heat sources of 1 mm x 1 mm and 3.4 mm x 3.3 mm, respectively. The 1 mm x 1 mm hotspot sustained a record high heat flux of 10,000 W center dot cm-2 with a temperature rise of 120 K, while the larger 3.4 mm x 3.3 mm heat source handled 1000 W center dot cm-2 with only a 42 K temperature rise. The corresponding effective convective heat transfer coefficients reached 1.3 x 105 W center dot m-2 center dot K-1 (50 mu m channels, large heat source) and 3.5 x 104 W center dot m-2 center dot K-1 (100 mu m channels, small heat source), among the highest values reported for single-phase microfluidic cooling. These results highlight the synergistic advantages of diamond's superior thermal conductivity and manifoldbased flow routing architectures. The FDMMHS demonstrates good potential for compact electronic systems requiring reliable heat management. It also provides a foundation for further optimization through advanced diamond microfabrication.

Hydrogen-terminated diamond (H-diamond) has emerged as a promising dopant-free p-type semiconductor owing to its distinctive surface conductivity. However, the development of H-diamond-based electronic devices remain constrained by their limited carrier mobility and poor environmental stability. In this work, we developed an innovative approach through conformal deposition of an amorphous carbon (a-C) layer on H-diamond surfaces via microwave plasma chemical vapor deposition. This engineered interface establishes a highly conductive channel exhibiting an unprecedented hole mobility exceeding 1470 cm(2)V(-1) s(-1), while maintaining optimal carrier density (similar to 10(12) cm(-2)) and remarkably low sheet resistance (2300 Omega/square). The modified surface demonstrates exceptional environmental stability, retaining its electrical properties for over two months under ambient conditions while maintaining excellent conductivity at elevated temperatures up to 575 K. Comprehensive characterization through photoluminescence spectroscopy, ultraviolet photoelectron spectroscopy, and comparative vacuum/ambient Hall measurements reveals a charge transfer doping mechanism predominantly mediated by the adsorbed a-C layer, with secondary contributions from ambient molecular species. This breakthrough provides critical insights for designing stable, high-performance H-diamond-based electronic systems for advanced applications in extreme environments.

The growing mechanism of diamond structure on Ti-coated carbon fiber (CF) surfaces and the corresponding progression of sp2-to-sp3 hybridization are clarified in this work. The critical factor governing the sp2-sp3 hybridization transition was determined to be hydrogen etching-induced topological defects at carbon nanowall (CNW) edges using microwave plasma chemical vapor deposition (MPCVD) in conjunction with multi-technique characterization. The process manifests three distinct stages: vertical CNW growth, nanodiamond nucleation transition, and epitaxial growth of cellular nanodiamond (C-ND). The hydrogen etching of prismatic CNW surfaces produces Stone-Wales defects, which cause localized lattice distortions and produce sp3-hybridized active sites, according to microscopic examination. The graphite-to-diamond phase transition is driven by these structural changes; quantitative EELS research confirms 68.06 % sp3 hybridization in advanced development stages. The essence of the structural shift from graphite to diamond is made clear by the defect-induced hybridization transition process. Additionally, it serves as an approach for designing carbon fiber-diamond composite electrode structures.

Gallium nitride (GaN) high-electron-mobility transistors are constrained by localized self-heating, which compromises reliability and limits power scaling. While diamond integration offers a superior thermal management solution, minimizing the thermal resistance of the near-junction passivation layers remains a critical challenge. This work demonstrates an effective top-side thermal management strategy by fabricating a GaN/AlN/diamond heterostructure, replacing the conventional low-thermal-conductivity SiN passivation. Enabled by a thin AlN interlayer, this architecture achieves an ultra-low thermal boundary resistance of 6.5 m2 & centerdot;K GW-1. Consequently, under a high power density of 24 W mm-1, transient thermal analysis reveals a significant peak junction temperature reduction of similar to 30 degrees C compared to standard SiN-passivated devices. Cross-sectional TEM and energy-dispersive x-ray spectroscopy confirm atomically abrupt interfaces without interdiffusion, validating the structural integrity. These results underscore the efficacy of eliminating the thermal barrier in the near-junction region, establishing a viable pathway for realizing the full potential of diamond-enhanced GaN electronics.

The 14N(p,1)15O reaction plays a crucial role in studies of hydrogen burning. Irradiation-resistant nitride targets are essential for extending direct measurements of this reaction to lower energies. In this work, we fabricated nitride targets using filter cathodic vacuum arc (FCVA) and low-pressure chemical vapor deposition (LPCVD) techniques. The thickness and chemical composition of the targets, as well as the impurity levels of the TiN targets, were evaluated through corresponding reaction measurements. The results indicate that FCVAfabricated TiN targets exhibit the best comprehensive performance. The deterioration of the TiN targets under the bombardment of a similar to 2 mA proton beam was investigated by monitoring the yield curves. The reduction rates of the atomic areal density for these targets were found to be in the range of 0.084-0.16%/C. The prepared TiN targets successfully advanced the measurement of 14N(p,1)15O reaction to Ep = 110 keV in a ground laboratory, which will enable further extension to Ep = 70 keV at the Jinping Underground Nuclear Astrophysics facility (JUNA) in the future.

Diamond exhibits exceptional physical and electronic properties, making it one of the most promising materials for high-frequency and high-power semiconductor devices. However, the application of diamond semiconductor devices requires an extremely low surface roughness (<1 nm). The surface finishing of super-hard diamond is complex and time-consuming, limiting their applicability to large-scale industrial production. In this study, the efficient polishing behavior of single-crystal diamond was developed based on a self-developed multi-component high-efficiency chemical mechanical polishing (CMP) slurry. An atomically ultra-smooth surface on single-crystal diamond was achieved within a short time, with a 50% improvement in efficiency compared to a commercial slurry. After 12 hours of polishing, the surface roughness over an area of 5 μm2 was reduced from Ra = 1.48 nm to Ra = 0.0866 nm. The effective removal of the subsurface damage layer was verified by cathodoluminescence (CL) analysis of the diamond. Particle size distribution, zeta potential, and XPS analyses demonstrated that the chemical synergy between SiO2 and Si in the self-developed multi-component slurry introduced more dissociable silanol groups. This increased the absolute zeta potential and significantly enhanced the electrostatic repulsion between abrasive particles to form a stable dispersion system. Simultaneously, the coupled chemical oxidation of the slurry enabled the rapid removal of the damaged layer predominantly in the form of Si–O–C species, thereby achieving a rapid reduction in roughness during the initial polishing stage. This work creates favorable conditions for advancing surface processing technologies for diamond semiconductors and technical support for the fabrication of high-performance diamond-based devices.

The formidable challenge of performance inhomogeneity hinders the application of large-diameter chemical vapor deposition (CVD) diamond wafers in high-reliability semiconductor and thermal management systems. This work elucidates the origin of the radial gradient in fracture strength within 8-inch freestanding diamond films prepared by direct current arc plasma jet CVD. Through a combination of high-speed imaging with optical filters, we quantitatively correlate the arc zonation (center, main, edge) with the spatial distribution of H-gamma and C-2 radicals. The results reveal that the region where the arc trunk contacts the substrate (radial position similar to 80 mm) exhibits the highest atomic hydrogen concentration, leading to the finest grain size, the lowest density of mesoscopic pores (as characterized by OM and Micro-CT), and consequently, the peak fracture strength of 1348.1 MPa. XFEM simulation confirms that pores act as potent stress concentrators for crack initiation. Crucially, by engineering the plasma morphology into an inverted "T" shape through multi-field coupling, we achieved a homogenized distribution of active species. This optimization yielded a wafer with a high average strength of 972.0 MPa and exceptional uniformity, reducing the strength deviation from 69.4% to 6.8%. This study provides a definitive process-structure-property relationship and a practical plasma-uniformity engineering strategy for manufacturing high-performance, large-area diamond wafers.

A laser-assisted post-growth processing route is demonstrated for thick DC arc jet CVD-grown polycrystalline diamond (PCD) plates intended for optical and photonic applications. Deep nanosecond laser cutting is used for planar removal of growth-related layers from both sides of the plate and for rapid leveling of the initially rough growth surface. This step is followed by mechanical polishing, which provides the final low-roughness optical surface. Optical interferometry shows that mechanical polishing reduces the surface roughness from the sub-micrometer level after laser cutting to an RMS value of approximately 15 nm, eliminating grain-related surface relief and strongly reducing surface scattering losses. Raman spectroscopy indicates temporary laser-induced surface disorder after cutting, which is fully removed by subsequent polishing, confirming elimination of the laser-affected layer. UV-Vis absorption reveals nitrogen-related coloration with an estimated nitrogen concentration of approximately 12 ppm, while transmission measurements demonstrate a progressive increase in optical transparency from the as-grown to laser-cut and polished states across the UV-Vis and IR spectral ranges. Room-temperature thermal conductivity remains high, k similar to (1.6 +/- 0.3) & times; 10(3) W m(-1) K-1, confirming preservation of bulk material quality. The combined laser-mechanical processing sequence is completed within 24 h and enables conversion of thick as-grown CVD PCD into double-side polished plates suitable for high-power optical windows, laser systems, and thermal photonic components.

Graphene/diamond heterostructures have attracted much attention by combining the high carrier mobility of graphene with the high phonon frequency of diamond. Here, Ni-catalyzed graphene/diamond heterostructures were formed on single-crystal diamond (100) substrate after a rapid high-temperature annealing. The influence of Ni catalyst thickness (10–100 nm) on graphene layers, surface morphology, and electrical properties was systematically investigated. Raman spectroscopy and conductive atomic force microscopy were firstly employed for its surface characterization. An increase in Ni catalyst thickness leads to a corresponding increase in the surface conductivity of the graphene/diamond heterostructures. Temperature-dependent electrical transport measurements from 2 to 400 K revealed an anomalous sharp drop in resistance near 100 K for the fabricated heterostructures. High-resolution transmission electron microscopy (HRTEM) analysis further revealed the presence of an sp²-sp³ hybridized layer at the graphene/diamond interface. The unique bonding configuration and electronic structure of this interfacial region may be responsible for inducing unconventional superconducting transport. However, further verification is required through more rigorous measurements. Our findings open up new opportunities for exploring exotic quantum phenomena at carbon-based heterointerfaces.