High-quality epitaxial Bi1-xSbx (BiSb) films were formed by two-step growth using molecular beam epitaxy. The use of two-step growth, which involves lower-temperature growth at ~150 °C followed by ...higher-temperature (~250 °C) growth, and lattice-matched substrates such as BaF2 (111) are key to obtain high-quality BiSb films. The composition of the BiSb films can also be systematically tuned using this growth procedure. The epitaxial BiSb films showed higher crystallinity (full width at half maximum: ~0.69°) and higher mobility (~2100 cm2/Vs), which indicate that sufficient quality films were obtained. Such films are expected to pave the way for the fabrication of electronic devices using topological BiSb.
•High-quality epitaxial BiSb films were formed by using molecular beam epitaxy.•Two-step growth and the use of lattice-matched substrates are necessary.•The BaF2 (111) substrate is one of the best substrates for the growth of BiSb films.
The formation of high-quality graphene layers on diamond was achieved based on a high-temperature annealing method using a Cu catalyst. Typical features of monolayer graphene were observed in the ...Raman spectra of layers formed by annealing of Cu/diamond heterostructures at 950°C for 90min. The coverage ratio of these graphene layers on diamond was estimated to be on the order of 85% by Raman mapping of the 2D peak. The sheet hole concentration and mobility values of the layers were estimated to be ~1013cm−2 and ~670cm2/Vs, respectively. These values are comparable to those previously observed for high-quality graphene layers on SiC.
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•The formation of high-quality graphene layers on diamond was achieved based on a high-temperature annealing method.•Typical features of monolayer graphene were observed in the Raman spectra of layers on diamond.•The sheet hole concentration and mobility values of the layers were estimated to be ~1013 cm−2 and ~670 cm2/Vs.
The identification of human CD34-negative (CD34(-)) hematopoietic stem cells (HSCs) provides a new concept for the hierarchy in the human HSC compartment. Previous studies demonstrated that CD34(-) ...severe combined immunodeficiency (SCID)-repopulating cells (SRCs) are a distinct class of primitive HSCs in comparison to the well-characterized CD34(+)CD38(-) SRCs. However, the purification level of rare CD34(-) SRCs in 18 lineage marker-negative (Lin(-)) CD34(-) cells (1/1000) is still very low compared with that of CD34(+)CD38(-) SRCs (1/40). As in the mouse, it will be necessary to identify useful positive markers for a high degree of purification of rare human CD34(-) SRCs. Using 18Lin(-)CD34(-) cells, we analyzed the expression of candidate positive markers by flow cytometric analysis. We finally identified CD133 as a reliable positive marker of human CB-derived CD34(-) SRCs and succeeded in highly purifying primitive human CD34(-) HSCs. The limiting dilution analysis demonstrated that the incidence of CD34(-) SRCs in 18Lin(-)CD34(-)CD133(+) cells was 1/142, which is the highest level of purification of these unique CD34(-) HSCs to date. Furthermore, CD133 expression clearly segregated the SRC activities of 18Lin(-)CD34(-) cells, as well as 18Lin(-)CD34(+) cells, in their positive fractions, indicating its functional significance as a common cell surface maker to isolate effectively both CD34(+) and CD34(-) SRCs.
High-temperature and high-voltage characteristics of Cu/diamond Schottky diodes were investigated. Cu Schottky diodes showed clear rectification up to ~700°C. The current–voltage characteristics of ...the diodes at 400°C were almost unchanged after keeping them for 30h, implying they have high stability at ~400°C. The diodes showed specific on-resistance and breakdown voltage of 83.4mΩcm2 and 713V at 400°C, respectively, which are comparable to reported highest values for diamond Schottky diodes and close to the theoretical limit for 6H-SiC at several hundred °C. These results indicate that Cu/diamond Schottky diodes are promising for high-temperature power applications.
•High-temperature and high-voltage characteristics of Cu/diamond Schottky diodes were investigated.•Cu/diamond Schottky diodes showed clear rectification up to ~700°C and have high stability at ~400°C.•The diodes showed specific on-resistance and breakdown voltage of 83.4mΩcm2 and 713V at 400°C.
The high-temperature characteristics of diamond Schottky diodes fabricated using Ag or Ni on in-situ boron-doped diamond were examined. Up to 600°C, Ag Schottky diodes exhibited a high rectification ...ratio of the order of 104. Even at ~750°C, their rectification ratio was about 10, indicating that diamond field effect transistors with Ag Schottky diodes can operate at this temperature. In contrast, Ni Schottky diodes did not show clear rectification above 600°C. An analysis of the I–V curves indicated that the Ag Schottky diodes have a higher rectification ratio than the Ni Schottky diodes at high temperatures due to their higher barrier heights (ϕB=~2.0 and ~0.7eV for Ag and Ni, respectively).
•We fabricated Schottky diodes and examined their high temperature characteristics.•Even at ~750°C, rectification ratio of Ag Schottky diodes was of the order of 10.•Schottky diodes with higher barrier heights worked at higher temperature.
We measured a set of π±Σ∓, π0Σ0, and π−Σ0 invariant mass spectra below and above the K¯N mass threshold in K−-induced reactions on deuteron. The measured πΣ mass spectral shape is well reproduced via ...the two-step mechanism, i.e., a neutron knocked out at a forward angle from a deuteron by an incident K−, with the K¯ recoiled backward reacting with the residual nucleon to produce π and Σ. We deduced the S-wave K¯N→πΣ and K¯N→K¯N scattering amplitudes in the isospin 0 channel in the framework of a K¯N and πΣ coupled channel. We find that a resonance pole corresponding to Λ(1405) is located at 1417.7−7.4+6.0 (fitting errors)−1.0+1.1 (systematic errors) + −26.1−7.9+6.0 (fitting errors)−2.0+1.7 (systematic errors) i MeV/c2, closer to the K¯N mass threshold than the value determined by the Particle Data Group.
While the electrical current manipulation of antiferromagnets (AFMs) has been demonstrated, the extent of the studied AFM materials has been limited with few systematic experiments and a poor ...understanding. We compare the electrical current switching of the exchange-bias field (Hex) in AFM-Mn3AN/ferromagnet-Co3FeN bilayers. An applied pulse current can manipulate Hex with respect to the current density and FM layer magnetization, which shifts exponentially as a function of the current density. We found that the saturation current density and exponential decay constant τ increase with the local moment of AFM Mn atoms. Our results highlight the effect of the AFM local moment to electrical current switching of Hex, although it has a near-zero net magnetization, and may provide a facile way to explore the electrical current manipulation of AFM materials.
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