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Eckstrom-Adcock iron carbide (Fe7C3) is considered to be the main constituent of the Earth’s inner core, owing to its low shear wave velocity. However, the crystal structure of Fe7C3 remains controversial and its thermoelastic properties are not well constrained at high temperature and pressure conditions. Based on the first-principles simulation method, we calculated the relative phase stability, equation of state, and sound velocity of Fe7C3 at core conditions. The results indicate that the orthorhombic phase of Fe7C3 is stable at core conditions. While Fe7C3 does reproduce the low shear wave velocity and high Poisson’s ratio of the inner core, its compressional wave velocity and density are 12% higher and 6% lower than those observed in seismic data, respectively. Therefore, we argue that carbon alone cannot completely explain the thermal properties of the inner core and the inclusion of other light elements may be required.

As a promising ultra-wide bandgap semiconductor material, gallium oxide (Ga2O3) is attracting an extensive attention of researchers due to its feasible growth process, appropriate bandgap of 4.4-5.3 eV allowing for deep-ultraviolet (deep-UV) detection, good physical and chemical stability, high breakdown field strength and electron mobility, etc. Different from the strict processes for controllable crystalline Ga2O3 (usually refer to stable monoclinic β-Ga2O3), amorphous Ga2O3 (a-Ga2O3) film can be prepared uniformly at low temperature on a large-area deposition substrate, suggesting great advantages such as low manufacturing cost and excellent flexibility, dispensing with high-temperature and high vacuum techniques. Thus, a-Ga2O3 extremely facilitates important applications in various applied fields. Therefore, in this concise review, we summarized several major deposition methods for a-Ga2O3 films, of which the characteristics were discussed. Additionally, potential methods to optimize the film properties were proposed by right of the inspiration from some recent studies. Subsequently, the applications of a-Ga2O3 thin films, e.g., in photodetectors, resistive random access memories (RRAMs) and gas sensors, were represented with a fruitful discussion of their structures and operating mechanisms.

In this paper, the dynamic self-heating effect (SHE) of silicon-on-insulator (SOI) MOSFETs is comprehensively evaluated by ultrafast pulsed I–V measurement. For the first time, it’s found that the complete heating response and cooling response of SHE for SOI MOSFETs are conjugated two-stage curves. We establish the effective thermal transient response model with stage superposition corresponding to the heating process. The systematic study of SHE dependence on workload shows that frequency and duty cycle have more significant effect on SHE in first-stage heating process than that in second stage. In the first-stage heating process, the peak lattice temperature and current oscillation amplitude respectively decrease by more than 25k and 4% with frequency increasing to 10M, and when duty cycle is reduced to 25%, the peak lattice temperature drops to 306k and current oscillation amplitude drops to 0.77%. Finally, the investigation of two-stage heating process provides a guideline for the unified optimization of dynamic SHE in terms of workload. As the operating frequency is raised to GHz, the peak temperature depends on duty cycle, and self-heating oscillation is completely suppressed.

Massive gas injection (MGI) is a traditional plasma disruption mitigation method. This method directly injects massive gas into the pre-disruption plasma and has been developed on EAST. Different noble gas injection experiments, including He, Ne, and Ar, were performed to compare the mitigation effect of plasma disruption by evaluating the key parameters such as flight time, pre-thermal quench (pre-TQ), and current quench (CQ). The flight time was shorter for low atomic number (Z) gas, and the decrease in flight time by increasing the amount of gas was insignificant. However, both pre-TQ and CQ durations decreased considerably with the increase in gas injection amount. The effect of atomic mass on pre-TQ and CQ durations showed the opposite trend. The observed trend could help in controlling CQ duration in a reasonable area. Moreover, the analysis of radiation distribution with different impurity injections indicates that low Z impurity could reduce the asymmetry of radiation, which is valuable in mitigating plasma disruption. These results provide essential data support for plasma disruption mitigation on EAST and future fusion devices.

A self-powered solar-blind ultraviolet (UV) photodetector (PD) was successfully constructed on a Ga2O3/Bi2WO6 heterojunction, which was fabricated by spin-coating the hydrothermally grown Bi2WO6 onto MOCVD-grown Ga2O3 film. The results show that a typical type-I heterojunction is formed at the interface of the Ga2O3 film and clustered Bi2WO6, which demonstrates a distinct photovoltaic effect with an open-circuit voltage of 0.18 V under the irradiation of 254 nm UV light. Moreover, the Ga2O3/Bi2WO6 PD displays excellent photodetection performance with an ultra-low dark current of ∼ 6 fA, and a high light-to-dark current ratio (PDCR) of 3.5 × 104 in self-powered mode (0 V), as well as a best responsivity result of 2.21 mA/W in power supply mode (5 V). Furthermore, the PD possesses a stable and fast response speed under different light intensities and voltages. At zero voltage, the PD exhibits a fast rise time of 132 ms and 162 ms, as well as a quick decay time of 69 ms and 522 ms, respectively. In general, the newly attempted Ga2O3/Bi2WO6 heterojunction may become a potential candidate for the realization of self-powered and high-performance UV photodetectors.

Exploring low-cost and high-performance catalysts for oxygen evolution reaction (OER) remains to be a great challenge. Iridium-based perovskite oxide has large potential in OER because of its intrinsic activity and outstanding physicochemical properties. In this study, iridium-doped strontium titanate (Ir-STO) solution is brushed on a Ti sheet by the traditional method to obtain the Ir-STO/Ti electrodes after being calcined at a high temperature. The microstructure and electrocatalysis properties of the Ir-STO are further modified by a facile and scalable NH3-plasma strategy. In addition to the doping of Ir, the NH3 plasma treatment further results in N-doping into Ir-STO, which enriches active species and causes oxygen vacancies near doped sites. The resulting N, Ir-STO/Ti electrode reveals excellent acidic OER activity with the lowest overpotential of 390 mV at 10 mA/cm2 and the smallest Tafel slope of 140 mV/dec after 10-min plasma treatment. Therefore, the great potential of activated N, Ir-STO/Ti is regarded as a catalyst for the OER, and thus making a new opportunity for developing other perovskite catalysts via NH3 plasma treatment.

Terbium gallium garnet (Tb3Ga5O12, TGG) crystal can be used to fabricate various magneto-optical devices due to its optimal Faraday effect. In this work, 400-keV He+ ions with a fluence of 6.0 × 1016 ions/cm2 are irradiated into the TGG crystal for the planar waveguide formation. The precise diamond blade dicing with a rotation speed of 2 × 104 rpm and a cutting velocity of 0.1 mm/s is performed on the He+-implanted TGG planar waveguide for the ridge structure. The dark-mode spectrum of the He+-implanted TGG planar waveguide is measured by the prism-coupling method, thereby obtaining the relationship between the reflected light intensity and the effective refractive index. The refractive index profile of the planar waveguide is reconstructed by the reflectivity calculation method. The near-field light intensity distribution of the planar waveguide and the ridge waveguide are recorded by the end-face coupling method. The He+-implanted and diamond blade-diced TGG crystal planar and ridge waveguides are promising candidates for integrated magneto-optical devices.

Dynamic states in mutual-coupled mid-infrared quantum cascade lasers (QCLs) were numerically investigated in the parameter space of injection strength and detuning frequency based on the Lang–Kobayashi equations model. Three types of period-one states were found, with different periods of injection time delay τ inj, 2τ inj, and reciprocal of the detuning frequency. Besides, square-wave, quasi-period, pulse-burst and chaotic oscillations were also observed. It is concluded that external-cavity periodic dynamics and optical modes beating are the mainly periodic dynamics. The interaction of the two periodic dynamics and the high-frequency dynamics stimulated by strong injection induces the dynamic states evolution. This work helps to understand the dynamic behaviors in QCLs and shows a new way to mid-infrared wide-band chaotic laser.

A 4×4 beta-phase gallium oxide (β-Ga2O3) deep-ultraviolet (DUV) rectangular 10-fingers interdigital metal-semiconductor-metal (MSM) photodetector array of high photo responsivity is introduced. The Ga2O3 thin film is prepared through the metalorganic chemical vapor deposition technique, then used to construct the photodetector array via photolithography, lift-off, and ion beam sputtering methods. The one photodetector cell shows dark current of 1.94 pA, photo-to-dark current ratio of 6×107, photo responsivity of 634.15 A⋅W−1, specific detectivity of 5.93×1011 cm⋅Hz1/2⋅W−1 (Jones), external quantum efficiency of 310000%, and linear dynamic region of 108.94 dB, indicating high performances for DUV photo detection. Furthermore, the 16-cell photodetector array displays uniform performances with decent deviation of 19.6% for photo responsivity.

Pyrite FeS2 exhibits an ultrahigh energy density (1671 W⋅h⋅kg−1, for the reaction of FeS2 + 4Li = Fe + 2Li2S) in secondary lithium-ion batteries, but its poor cycling stability, huge volume expansion, the shuttle effect of polysulfides, and slow kinetic properties limit its practical application. In this work, we synthesize a composite structure material CoS on FeS2 surface (FeS x @CoS, 1 < x ≤ 2) by using a cobalt-containing MOF to improve its cycle stability. It is found that CoS inhibits the side reactions and adsorbs polysulfides. As a result, the modified FeS2 shows a higher discharge capacity of 577 mA⋅h⋅g−1 (919 W⋅h⋅kg−1) after 60 cycles than 484 mA⋅h⋅g−1 (778 W⋅h⋅kg−1) of bare pyrite FeS2. This efficient strategy provides a valuable step toward the realization of high cycling stability FeS2 cathode materials for secondary lithium-ion batteries and enriches the basic understanding of the influence of FeS2 interfacial stability on its electrochemical performances.

We systematically investigate the four-wave mixing (FWM) spectrum in a dual-cavity hybrid optomechanical system, which is made up of one optical cavity with an ensemble of two-level atoms and another with a mechanical oscillator. In this work, we propose that the hybrid dual-cavity optomechanical system can be employed as a highly sensitive mass sensor due to the fact that the FWM spectrum generated in this system has a narrow spectral width and the intensity of the FWM can be easily tuned by controlling the coupling strength (cavity–cavity, atom–cavity). More fascinatingly, the dual-cavity hybrid optomechanical system can also be used as an all-optical switch in view of the easy on/off control of FWM signals by adjusting the atom-pump detuning to be positive or negative. The proposed schemes have great potential applications in quantum information processing and highly sensitive detection.

Van der Waals (vdW) heterostructures have attracted significant attention because of their widespread applications in nanoscale devices. In the present work, we investigate the electronic structures of germanane/antimonene vdW heterostructure in response to normal strain and an external electric field by using the first-principles calculations based on density functional theory (DFT). The results demonstrate that the germanane/antimonene vdW heterostructure behaves as a metal in a [−1, −0.6] V/Å range, while it is a direct semiconductor in a [−0.5, 0.2] V/Å range, and it is an indirect semiconductor in a [0.3, 1.0] V/Å range. Interestingly, the band alignment of germanane/antimonene vdW heterostructure appears as type-II feature both in a [−0.5, 0.1] range and in a [0.3, 1] V/Å range, while it shows the type-I character at 0.2 V/Å. In addition, we find that the germanane/antimonene vdW heterostructure is an indirect semiconductor both in an in-plane biaxial strain range of [−5%, −3%] and in an in-plane biaxial strain range of [3%, 5%], while it exhibits a direct semiconductor character in an in-plane biaxial strain range of [−2%, 2%]. Furthermore, the band alignment of the germanane/antimonene vdW heterostructure changes from type-II to type-I at an in-plane biaxial strain of –3%. The adjustable electronic structure of this germanane/antimonene vdW heterostructure will pave the way for developing the nanoscale devices.

We propose schemes to realize quantum state transfer and prepare quantum entanglement in coupled cavity and cavity–fiber–cavity systems, respectively, by using the dressed state method. We first give the expression of pulses shape by using dressed states and then find a group of Gaussian pulses that are easy to realize in experiment to replace the ideal pulses by curve fitting. We also study the influence of some parameters fluctuation, atomic spontaneous emission, and photon leakage on fidelity. The results show that our schemes have good robustness. Because the atoms are trapped in different cavities, it is easy to perform different operations on different atoms. The proposed schemes have the potential applications in dressed states for distributed quantum information processing tasks.

We theoretically investigate the quantum enhanced metrology using two-mode squeezed twin-Fock states and parity detection. Our results indicate that, for a given initial squeezing parameter, compared with the two-mode squeezed vacuum state, both phase sensitivity and resolution can be enhanced when the two-mode squeezed twin-Fock state is considered as an input state of a Mach–Zehnder interferometer. Within a constraint on the total photon number, although the two-mode squeezed vacuum state gives the better phase sensitivity when the phase shift φ to be estimated approaches to zero, the phase sensitivity offered by these non-Gaussian entangled Gaussian states is relatively stable with respect to the phase shift itself. When the phase shift slightly deviates from φ = 0, the phase sensitivity can be still enhanced by the two-mode squeezed twin-Fock state over a broad range of the total mean photon number where the phase uncertainty is still below the quantum standard noise limit. Finally, we numerically prove that the quantum Cramér–Rao bound can be approached with the parity detection.

We present a method to extend the operating wavelength of the interband transition quantum well photodetector from an extended short-wavelength infrared region to a middle-wavelength infrared region. In the modified InAsSb quantum well, GaSb is replaced with AlSb/AlGaSb, the valence band of the barrier material is lowered, the first restricted energy level is higher than the valence band of the barrier material, the energy band structure forms type-II structure. The photocurrent spectrum manifest that the fabricated photodetector exhibits a response range from 1.9 μm to 3.2 μm with two peaks at 2.18 μm and 3.03 μm at 78K.

Four-wave-mixing (FWM) process is examined by using density matrix formalism in a periodically-driven atomic medium. Numerical result shows that FWM signals can be controlled by selecting different dynamic parameters of the probe field and strengths of the inner-dressing fields. It is also shown that the controllable FWM process is dominantly influenced by the evolution of atomic population difference and two-photon coherence. This dynamic and inner-dressing control of FWM is probably used for optimizing the optical nonlinear process and information processing.

Magnetic oxide semiconductors are significant spintronics materials. In this article, we review recent advances for homogeneous and inhomogeneous magnetic oxide semiconductors. In the homogeneous magnetic oxide semiconductors, we focus on the various doping techniques including choosing different transition metals, codoping, non-magnetic doping, and even un-doping to realize homogeneous substitution and the clear magnetic origin. And the enhancement of the ferromagnetism is achieved by nanodot arrays engineering, which is accompanied by the tunable optical properties. In the inhomogeneous magnetic oxide semiconductors, we review some heterostructures and their magnetic and transport properties, especially magnetoresistance, which are dramatically modulated by electric field in the constructed devices. And the related mechanisms are discussed in details. Finally, we provide an overview and possible potential applications of magnetic oxide semiconductors.

We investigate the sensitivity of phase estimation in a Mach–Zehnder interferometer with photon-subtracted two-mode squeezed vacuum states. Our results show that, for given initial squeezing parameter, both symmetric and asymmetric photon subtractions can further improve the quantum Cramér–Rao bound (i.e., the ultimate phase sensitivity), especially for single-mode photon subtraction. On the other hand, the quantum Cramér–Rao bound can be reached by parity detection for symmetric photon-subtracted two-mode squeezed vacuum states at particular values of the phase shift, but it is not valid for asymmetric photon-subtracted two-mode squeezed vacuum states. In addition, compared with the two-mode squeezed vacuum state, the phase sensitivity via parity detection with asymmetric photon-subtracted two-mode squeezed vacuum states will be getting worse. Thus, parity detection may not always be the optimal detection scheme for nonclassical states of light when they are considered as the interferometer states.