Hitoshi Sumiya

High-precision nanoscale temperature sensing using single defects in diamond.

Measuring local temperature with a spatial resolution on the order of a few nanometers has a wide range of applications in the semiconductor industry and in material and life sciences. For example, probing temperature on the nanoscale with high precision can potentially be used to detect small, local temperature changes like those caused by chemical reactions or biochemical processes. However, precise nanoscale temperature measurements have not been realized so far owing to the lack of adequate probes. Here we experimentally demonstrate a novel nanoscale temperature sensing technique based on optically detected electron spin resonance in single atomic defects in diamonds. These diamond sensor sizes range from a micrometer down to a few tens of nanometers. We achieve a temperature noise floor of 5 mK/Hz(1/2) for single defects in bulk sensors. Using doped nanodiamonds as sensors the temperature noise floor is 130 mK/Hz(1/2) and accuracies down to 1 mK for nanocrystal sizes and therefore length scales of a few tens of nanometers. This combination of precision and position resolution, combined with the outstanding sensor photostability, should allow the measurement of the heat produced by chemical interactions involving a few or single molecules even in heterogeneous environments like cells.

High-pressure synthesis of high-purity diamond crystal

High-purity type IIa diamond crystals of weight 1–2 carats, containing less than 0.1 ppm chemical impurities and few inclusions, have been successfully synthesized by a temperature gradient method at high pressures and temperatures. The concentration of nitrogen impurities in the diamond crystals was reduced to less than 0.1 ppm by adding an element of the IVa group to the solvent as a nitrogen getter. The boron impurity concentration was reduced to less than 0.1 ppm by using a high-purity graphite (<1 ppm impurities) as the carbon source. Nickel impurities were avoided by using an Fe-Co alloy system for the solvent. Furthermore, by adding elements which can reduce the formation of carbides such as TiC or ZrC in the solvent, inclusions of the carbide or the solvent metal in the diamond crystal were substantially decreased, and consequently good-quality type IIa diamond crystals were obtained even at a growth rate as high as 2–3 mg h−1.

Observation of discrete time-crystalline order in a disordered dipolar many-body system

Understanding quantum dynamics away from equilibrium is an outstanding challenge in the modern physical sciences. Out-of-equilibrium systems can display a rich variety of phenomena, including self-organized synchronization and dynamical phase transitions. More recently, advances in the controlled manipulation of isolated many-body systems have enabled detailed studies of non-equilibrium phases in strongly interacting quantum matter; for example, the interplay between periodic driving, disorder and strong interactions has been predicted to result in exotic ‘time-crystalline’ phases, in which a system exhibits temporal correlations at integer multiples of the fundamental driving period, breaking the discrete time-translational symmetry of the underlying drive. Here we report the experimental observation of such discrete time-crystalline order in a driven, disordered ensemble of about one million dipolar spin impurities in diamond at room temperature. We observe long-lived temporal correlations, experimentally identify the phase boundary and find that the temporal order is protected by strong interactions. This order is remarkably stable to perturbations, even in the presence of slow thermalization. Our work opens the door to exploring dynamical phases of matter and controlling interacting, disordered many-body systems.

Real-Time Background-Free Selective Imaging of Fluorescent Nanodiamonds in Vivo

Recent developments of imaging techniques have enabled fluorescence microscopy to investigate the localization and dynamics of intracellular substances of interest even at the single-molecule level. However, such sensitive detection is often hampered by autofluorescence arising from endogenous molecules. Those unwanted signals are generally reduced by utilizing differences in either wavelength or fluorescence lifetime; nevertheless, extraction of the signal of interest is often insufficient, particularly for in vivo imaging. Here, we describe a potential method for the selective imaging of nitrogen-vacancy centers (NVCs) in nanodiamonds. This method is based on the property of NVCs that the fluorescence intensity sensitively depends on the ground state spin configuration which can be regulated by electron spin magnetic resonance. Because the NVC fluorescence exhibits neither photobleaching nor photoblinking, this protocol allowed us to conduct long-term tracking of a single nanodiamond in both Caenorhabditis elegans and mice, with excellent imaging contrast even in the presence of strong background autofluorescence.

Microstructure features of polycrystalline diamond synthesized directly from graphite under static high pressure

Recently, ultra-hard polycrystalline diamond was synthesized from graphite by direct conversion under static high pressure. This paper describes the microstructure features of thus formed polycrystalline diamond. Transmission electron microscopy and electron diffraction have revealed that the polycrystalline diamond has a mixed texture of a homogeneous fine structure and a lamellar structure. The former structure consists of fine-grained diamond particles of several tens of nanometers across, which are randomly oriented. The latter structure has bending diamond layers, which may reflect deformed shapes of locally layered graphite of starting material. The experimental results suggest that diamond particles in the homogeneous fine structure are transformed from graphite in the diffusion process, while diamond layers in the lamellar structure are formed in the martensitic process from graphite via the hexagonal diamond phase. It is also noted that significant grain growth occurred at a high temperature of ∼2700°C, and the lamellar structure was segmentalized to form new grain boundaries.

Crystalline perfection of high purity synthetic diamond crystal

Crystalline quality of high purity synthetic diamond crystals (type IIa) with impurities less than 0.1 ppm grown by a temperature gradient method under high-pressure and high-temperature has been investigated in detail. The crystal defects and internal strains of the synthetic type IIa diamonds were studied by double-crystal X-ray rocking curve measurement, polarizing microscopy, X-ray topography and Raman spectroscopy. The synthetic type IIa diamonds were found to have high crystalline quality with fewer crystal defects, less internal strain and less variation in defects among crystals than those of natural diamonds or synthetic type Ib diamonds. However, in the synthetic type IIa diamond crystal some line and plane defects were observed. It was found that by using strain-free and low defect crystals for the seeds, the line defects (dislocation bundles) could be removed, thereby improving the crystalline quality of the synthetic type IIa diamonds.

Mechanical properties of high purity polycrystalline cBN synthesized by direct conversion sintering method

Mechanical properties of high purity polycrystalline cBN sintered bodies synthesized by the direct conversion method under high pressure and high temperature have been investigated by hardness and transverse rupture strength (TRS) measurement in the temperature range of 20–1200 °C. It was confirmed that the hardness and TRS of the polycrystalline cBN depends strongly on the cBN grain size and the amount of residual (compressed) hBN in the sintered body. The fine-grained (<0.5 μm) and high purity (cBN > 99.9%) polycrystalline sintered body synthesized at 7.7 GPa, 2200–2400°C has highest hardness and TRS at any temperature. The TRS of the sintered body shows a positive temperature dependence up to 1200 °C. The high hardness and high TRS at high temperature of the fine-grained high purity polycrystalline cBN suggest that the sintered body has high potential in cutting tool uses.

Mechanical properties of synthetic type IIa diamond crystal

Abstract The mechanical behavior of synthetic type IIa diamond has been investigated by the Knoop hardness measurement and observation of the cleavage surfaces. It was clarified that the Knoop hardness in (100)〈100〉 of synthetic diamonds increases with decreasing of the nitrogen impurities concentration, and that the synthetic type IIa diamond, having few nitrogen impurities, has the highest hardness of synthetic diamonds. In addition, it was found that the Knoop hardness in (100)〈110〉 of synthetic type IIa diamond is extremely high, and the anisotropy in the hardness of the diamond is different from those of natural diamond and synthetic type Ib diamond. The cleavage surfaces of the synthetic type IIa diamonds were very smooth and showed remarkably regular cleavage patterns. These results indicate that there are very few impurities and crystal defects in the synthetic type IIa diamond, and also suggest that the diamond has high resistance to plastic flow.

Electronic structure of the negatively charged silicon-vacancy center in diamond

The negatively-charged silicon-vacancy (SiV

Subpicotesla Diamond Magnetometry

^-