In this study, a single-crystal diamond (SCD) MEMS cantilever was fabricated using a buried graphite sacrificial-layer process. A region containing nitrogen-vacancy (NV) centers formed near the ion-implantation-induced defective layer was directly utilized as the stress-sensing region of the released cantilever, enabling dynamic stress sensing without the use of externally attached nanodiamonds. We investigated the relationship between the stress induced by the cantilever vibration and the peak shift of the fluorescence intensity of the optically detected magnetic resonance (ODMR) spectrum. By approximately aligning the static magnetic field with one of the four NV-center crystallographic axes, we were able to evaluate the dependence of the peak shift on stress. Our findings revealed that the peak shift can effectively detect uniaxial stress due to normal vibration. In addition, as the vibration amplitude increased, the magnitude of the ODMR peak shift also increased, showing a trend consistent with previously reported NV-center stress responses. Furthermore, the ODMR shift exhibited periodic modulation corresponding to the cantilever’s vibration phase. These results indicate that NV centers in micromachined SCD cantilevers can be used to detect vibration-induced dynamic bending stress.
Polycrystalline diamond films and coatings are widely used in optical components, thermal management, and cutting tools. Chemical vapor deposition (CVD) is widely used for their synthesis, while the initial nucleation stage largely determines the continuity and morphology of the diamond layer. Conventional nucleation is achieved by surface seeding with nanodiamond particles. An alternative approach is chemical nucleation, extensively studied for carbon-containing precursors and polymers, whereas nucleation on non-carbon particles remains comparatively unexplored. Here, lithium fluoride (LiF) particles were used as a model non-carbon system to study diamond nucleation and subsequent growth in CH4–H2 microwave plasma CVD. Surface morphology and Raman spectroscopy showed that LiF promotes localized formation of well-faceted diamond crystallites without conventional nanodiamond seeding. Increasing the substrate temperature to 900°C produced a nearly linear increase in nucleation density and enabled the formation of nearly continuous polycrystalline films, whereas further heating to 950°C promoted island-like growth despite increasing growth rate. Methane concentration mainly affected the growth regime: at CH4 contents of 10% and higher, secondary nucleation became pronounced, suppressing crystallite enlargement and promoting the transition from microcrystalline to nanocrystalline diamond. Raman analysis showed that substrate temperature had little effect on the sp3/sp2 ratio, although the diamond Raman line broadened at higher temperatures, whereas elevated methane concentrations increased the contribution of non-diamond carbon phases. These findings suggest that non-carbon chemical nucleation can provide a new perspective on diamond formation during CVD, including the emergence of diamond nuclei under conditions where diamond remains thermodynamically metastable.
Alumina (Al2O3) ceramics with complex geometry are widely used in aerospace thermal components, cutting tools, and catalyst supports because of their excellent thermal stability, corrosion resistance, and wear resistance. However, low ductility problem existed in such brittle material and influences its long-term stable service in extreme environments, especially under load-bearing conditions. Adding carbon material were considered as an effective method to improve mechanical properties of ceramics. In this work, diamond/Al2O3 composites were fabricated using digital light processing (DLP) additive manufacturing technology. Meanwhile, their microstructure, phase composition, and compressive properties were systematically investigated here. After sintering treatment, Al2O3 particles retained a well-defined morphology and unchanged phase composition, which had an average particle size of 6 μm. Diamond particles had an average particle size of 1 μm and transformed obviously from a crystalline structure to an amorphous state, accompanied by characteristic graphitization peaks. From mechanical properties testing results of DLP composites, the specimens exhibited elastic modulus of 331.23 ± 8.69 MPa and compressive strength of 46.19 ± 1.07 MPa. Specially, diamond/Al2O3 composites specimens had an increasing in elongation (27.26 ± 0.17%) compared with pure Al2O3 specimens. This indicated carbonized diamond particles had a positive effect on enhancing the ductility of Al2O3 ceramics. These scientific finding will provided an important reference for investigating additive manufacturing high-performance ceramics.
Boron and nitrogen co-doped diamond (BNDD) has attracted extensive research attention owing to its promising potential for n-type conductivity. However, boron–nitrogen (B–N)-related complexes in BNDD lead to highly complex optoelectronic properties, which hinders its practical applications. In this study, we present a systematic investigation of the electrical and optical properties of BNDDs with graded nitrogen doping, both in the as-grown state and after high-pressure high-temperature (HPHT) annealing. Nitrogen incorporation is found to sharply increase the resistivity of boron-doped diamond, dominated by enhanced hole scattering from nitrogen-associated defects and impurities. Following HPHT annealing, all BNDDs maintain stable p-type conduction with an elevated hole concentration, which benefits from the combined effects of neutral boron acceptor activation and intrinsic B–N complex dissociation. Strikingly, donor–acceptor pair (DAP) recombination luminescence appears concurrently with a drop in hole concentration in high-nitrogen BNDDs annealed above 2000 °C, directly confirming neutral nitrogen donor activation under HPHT conditions. This work provides a practical strategy for the performance modulation and optimization of BNDD, and reveals the activation effect of HPHT annealing on nitrogen impurities, providing a feasible path toward the realization of n-type diamond.
