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The growth of two-dimensional van der Waals magnetic materials presents attractive opportunities for exploring new physical phenomena and valuable applications. Among these materials, Fe3GeTe2 (FGT) exhibits a variety of remarkable properties and has garnered significant attention. Herein, we have for the first time created a nanomesh structure—a honeycomb-like array of hexagonal nanopores—with the zigzag pore-edge atomic structure on thin FGT flakes with and without oxidation of the pore edges. It is revealed that the magnitude of ferromagnetism (FM) significantly increases in both samples compared with bulk flakes without nanomeshes. Critical temperature annealing results in the formation of zigzag pore edges and interpore zigzag-edge nanoribbons. We unveil that the non-oxide (O) termination of the Fe dangling bonds on these zigzag edges enhances FM behavior, while O-termination suppresses this FM by introducing antiferromagnetic behavior through edge O–Fe coupling. FGT nanomeshes hold promise for the creation of strong FM and their effective application in magnetic and spintronic systems. [ABSTRACT FROM AUTHOR]

Strontium titanate [SrTiO3 (STO)], a perovskite oxide with an extremely high gate-tunable dielectric constant (ε) due to quantum paraelectric phases, is attracting considerable attention for yielding various physical phenomena when two-dimensional (2D) layers are integrated. Superconductivity is such a typical phenomenon. However, the influence of the STO substrates on enhancing transition temperatures (Tc) for (atomically) thin 2D flakes attached to them has been rarely investigated. Here, we report gate-tunable and gradual four-terminal resistance drops with critical onset T (TCR) and scanning tunneling spectroscopy (STS) spectra in devices comprising thin TaS2 flakes attached on monolayer hexagonal boron nitride (hBN) spacer/STO substrates. Observation of STS spectra confirms the presence of local superconducting gaps Δ (∼1.5 meV) with transition T (TΔC) three-times higher than previous reports of Tc under absent pressure and strong position dependence of Δ. Depending on Δ on back gate voltages (Vbg) and magnetic fields, there is a strong correlation between TCR and the onset Tc of superconductivity, implying an enhancement of approximately five times compared with the previous highest-onset Tc values without pressure as the applied Vbg increases. The high onset Tc and Δ are discussed based on screening of the long-range Coulomb interaction (CI) due to the high-ε of SrTiO3, while the short-ranged CI remains strong in the 2D limit, causing the superconductivity. Using a monolayer hBN/SrTiO3 substrate with Vbg opens doors to Tc enhancement in thin superconducting layers integrated on it and wide application due to the solid-state high-ε substrates. [ABSTRACT FROM AUTHOR]

Atomically thin two-dimensional transition-metal dichalcogenide materials with van der Waals integration provide various interesting optoelectronic characteristics that can be used to realize highly efficient flexible solar cells and photosensors. We previously reported in-plane lateral one-dimensional Schottky junctions (SJs) on few-atom-layer 2H-phase semiconductor-molybdenum disulfide by forming a 1T′-metal phase using laser beam (LB) irradiation and clarified their unique optoelectronic properties. Although the LB-derived 1T′/2H phase SJs provided efficient photocurrent generation, they had a large number of defects owing to the excess heat accumulation caused by the LB. Here, we observe partial electric hysteresis properties in photogenerated currents (Iphoto) on the SJs under reverse bias voltage regions and reveal that they are very sensitive to the voltage sweep direction and its switching (holding) time. The properties persist under dark ambient conditions for a few minutes, even after photo-irradiation is complete. The temperature dependence reveals that a defect-derived deep carrier trap-center, which is unique to the present 1T′ phase, can be the cause of these phenomena. A larger Iphoto and an increase in photogeneration efficiency are obtained by eliminating this trap center through thermal annealing. In contrast, it is expected that these hysteresis properties lead to atomically thin photo-memristor devices for opto-neuromorphic systems. [ABSTRACT FROM AUTHOR]

The authors have previously developed and proposed methods to estimate the in situ rock strength and moth wear while drilling with roller-cone bits [Karasawa et al., 2002, ASME J. Energy Resour. Technol. 124, pp. 125-132 (Pt. 1) 133-140 (Pt. 2)]. The purpose of this paper is to provide a follow-up to these two reports and to propose, for both previous methods, alternate techniques that can be more readily implemented in the field than those originally presented. The data presented in Part 1 of the previously mentioned work [I] were reanalyzed in order to find a new and simple parameter that can be used to estimate rock strength. This parameter uses only one set of data that consists of bit weight, torque, penetration rate, rotary speed, and bit diameter. It was also demonstrated that the effect of tooth wear on this new parameter is small. In addition, more practical methods, which employ two parameters, are derived and proposed to evaluate the tooth wear of rollercone bits.

New methods to estimate both the rock strength and tooth wear while drilling with roller-bits were developed and proposed in Part 1. These methods were derived from the results of drilling tests using milled-tooth type three-cone bits with different amounts of tooth wear. In this report, these methods were extended and applied to insert type three-cone bits. The validity of the test and data analyses techniques of Part 1 were confirmed for insert bits. The methods to estimate the tooth wear proposed in Part 1 were based on the drillability strength of rock. A new approach to determine the tooth wear is presented. This new approach could be more readily applied to evaluating tooth wear when compared to the previous methods based on the drillability strength of rock. [DOI: 10.1115/1.1482406]

This paper proposes new methods to estimate both the rock strength and tooth wear while drilling with roller-bits. Laboratory drilling tests were conducted to obtain the penetration rate, bit weight and torque using milled-tooth bits with different tooth wear (T0, T4, T7). Drilling media used for the tests were soft to medium-hard rocks whose uniaxial compressive strength ranged from 14 to 118 MPa. Based on the test results, a parameter, which presents the rock strength independent of the tooth wear, was first investigated. The investigation revealed that a parameter related to the axial energy and the rotary energy required to drill rock is effective to estimate the rock strength independent of the tooth wear. Second, methods to estimate the tooth wear were studied based on the same parameter that represents the rock strength. From the results of this study, methods to measure the tooth wear are proposed. [DOI: 10.1115/1.1482405]