Nano‐polycrystalline diamond (NPD) Irifune et al. (2003), Nature (London), 421, 599 has been used to obtain a glitch‐free X‐ray absorption spectrum under high pressure. In the case of conventional ...single‐crystal diamond (SCD) anvils, glitches owing to Bragg diffraction from the anvils are superimposed on X‐ray absorption spectra. The glitch has long been a serious problem for high‐pressure research activities using X‐ray spectroscopy because of the difficulties of its complete removal. It is demonstrated that NPD is one of the best candidate materials to overcome this problem. Here a glitch‐free absorption spectrum using the NPD anvils over a wide energy range is shown. The advantage and capability of NPD anvils is discussed by a comparison of the glitch map with that of SCD anvils.
The effects of thermal annealing on stacking faults and dislocations in single-crystal diamonds with a low defect density were investigated by synchrotron X-ray topography. We compared the X-ray ...topography images before and after annealing under various diffraction conditions. We found that the stacking faults disappeared after annealing, and new dislocations appeared at the edges of disappeared stacking faults. These results indicate that the stacking faults were Shockley type, and they were sandwiched between two Shockley partial dislocations. Therefore, we concluded that the Shockley stacking faults disappeared as a result of the movement of the Shockley partial dislocations. Before annealing, the perfect dislocations were straight along the 21¯1 direction; annealing caused these dislocations to bend along the 11¯0 and 101 directions. We identified two dislocation shapes; upper bending and lower bending dislocations. An analysis based on contrast extinction criterion; indicated that the bending direction depends on the Burgers vector, for example, a dislocation with b=a/2101 moved along the 011¯ direction, and a dislocation with b=a/211¯0 moved along the 011 direction.
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•The annealing effects of diamond single crystal were investigated by synchrotron X-ray topography.•Shockley stacking faults were disappeared due to the movement of Shockley partial dislocations.•Dislocations with b=a/2〈110〉 were bent along the 〈110〉 direction.
Magnetic field sensors that exploit quantum effects have shown that they can outperform classical sensors in terms of sensitivity enabling a range of novel applications in future, such as a brain ...machine interface. Negatively charged nitrogen‐vacancy (NV) centers in diamond have emerged as a promising high sensitivity platform for measuring magnetic fields at room temperature. Transferring this technology from laboratory setups into products and applications, the total size of the sensor, the overall power consumption, and the costs need to be reduced and optimized. Here, a fiber‐based NV magnetometer featuring a complete integration of all functional components is demonstrated without using any bulky laboratory equipment. This integrated prototype allows portable measurement of magnetic fields with a sensitivity of 344 pT Hz−1/2.
Negatively charged nitrogen‐vacancy centers in diamond are a promising candidate for high sensitive magnetometers enabling wide range of applications. Transferring this technology into products, this sensor needs to be miniaturized and integrated such that it can be portably used without the requirement of bulky laboratory equipment. A portable prototype of a fiber‐integrated magnetometer with sub‐nanotesla sensitivity is demonstrated.
Abstract
Quantum sensors are known for their high sensitivity in sensing applications. However, this sensitivity often comes with severe restrictions on other parameters which are also important. ...Examples are that in measurements of arbitrary signals, limitation in linear dynamic range could introduce distortions in magnitude and phase of the signal. High frequency resolution is another important feature for reconstructing unknown signals. Here, we demonstrate a distortion-free quantum sensing protocol that combines a quantum phase-sensitive detection with heterodyne readout. We present theoretical and experimental investigations using nitrogen-vacancy centers in diamond, showing the capability of reconstructing audio frequency signals with an extended linear dynamic range and high frequency resolution. Melody and speech based signals are used for demonstrating the features. The methods could broaden the horizon for quantum sensors towards applications, e.g. telecommunication in challenging environment, where low-distortion measurements are required at multiple frequency bands within a limited volume.
Dry etching using oxygen plasma was conducted on a single-point cutting tool made of nano-polycrystalline diamond to clarify the shapeable cutting edge radius (CER). The CER of the tool was measured ...by atomic force microscopy (AFM). The cantilever employed was made of single crystal silicon and had a tetrahedral shape with a probe tip radius of 4 to 10 nm. The CER can be identified by subtracting the probe tip radius from a measured CER when the probe tip radius is fixed at a certain value. Dry etching tests revealed that the measured CER decreased and converged to a constant value equivalent to the probe tip radius with increasing etching time. Utilizing this phenomenon, a standard tool suitable for calibrating the probe tip radius was fabricated. The CER and the variation in the CER of the standard tool were less than 0.1 nm. This calibration using the standard tool made it possible to identify the CER from the measured CER. It became clear that the CER converged to less than 0.1 nm, and the variation in converged CER was less than 0.5 nm. Hence, it can be concluded that the shapeable CER that can be formed by dry etching using oxygen plasma is less than 0.5 nm.
A research project was conducted to develop a grinding tool made of nano-polycrystalline diamond adaptable to fabricating a microdimple array (MDA) mold composed of a huge number of microdimples with ...a diameter of 30 μm, zero flattening, and a surface roughness of less than 10 nmRz on a surface of cemented carbide with a hardness of 2620 Hv. Eight spiral grooves twisted clockwise and counterclockwise and 7 μm in width and depth were formed on a hemispherical working surface with a radius of 0.1 mm to increase the ratio of actual depth of cut (ADC) that represents a specific grinding force. A set of a grinding test, the fabrication of MDA composed of 2107 microdimples and the measurement of the ADC by forming 18 microdimples before and after the MDA fabrication, was performed twice to evaluate the wear resistance of the grinding tool. The grinding test using the grinding tool with grooves twisted counterclockwise revealed that the tool enabled us to increase the ADC by 1.5-fold, compared with the tool without grooves, and that 4214 micrpdimples with a diameter flattening of less than 0.01 and a surface roughness of less than 10 nmRz were successively fabricated. Although it was difficult to fabricate these 4214 microdimples without any diameter change, the standard variation of the microdimple diameter was 0.07 μm when the ADC of the grinding tool became stable with the fabrication of more than 3000 microdimples.
For quantum sensing, it is vital to develop an efficient technique for determining the quantum state of the sensor. We optimize the weighting of the photoluminescence intensity for readout of the ...spin state of the nitrogen-vacancy (NV) center in diamond. We find that adopting a physical model that considers the optical transitions and relaxations of the NV center allows for an efficient readout. Our method improves the signal-to-noise ratio of the readout by 5.4% in a short time of 3 s, while the existing methods typically require 1 min of integration time. We also show that our technique enhances the readout of the nuclear spin memory. The demonstrated way is helpful for a wide range of measurements, from a few minutes to several days.
The polishing mechanisms and surface damages of mechanically and chemically polished diamond crystals were investigated. A metal bonded diamond wheel was used for mechanical polishing, while an SiO2 ...wheel was used for chemical polishing. After polishing, samples underwent surface treatment with hydrogen plasma to exhibit negative electron affinity. SEM observation revealed that the scratches consisted of dark cracks with cleavage facets. Dark contrast was observed around the cracks on the hydrogen terminated diamond surface, indicating that carriers excited by primary electrons were eliminated by crystal defects around the cracks. The polishing rate increased nonlinearly with the rotating speed of the SiO2 wheel. The difference of polishing rate of the (100) surface between the direction and the direction became smaller when using the SiO2 wheel than when using the metal bonded diamond grinding wheel. The polishing rates became more isotropic, suggesting that the wear reactions of the diamond and the SiO2 wheel were mainly chemical. Although abrasion traces were also observed by optical microscopy on the sample polished by an SiO2 wheel, dark contrast due to lattice distortion or crystal defects was not observed by SEM. This result shows that the sample surface and subsurface chemically polished by the SiO2 wheel had very little damages.
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•The mechanical and the chemical polishings of diamonds were investigated.•A metal bonded diamond wheel and an SiO2 wheel were used for the mechanical and the chemical polishing.•The mechanical polishing damages were seen by SEM by terminating the type IIa diamond with hydrogen.•The anisotropy of the chemical polishing rates was smaller than that of the mechanical ones.•The diamond surface chemically polished by the SiO2 wheel had very little damages.
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