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Since the discovery of symmetric helical interactions in the spin-orbit coupled single-band Hubbard model by Moriya and Kaplan, Shekhtman, Entin, Aharony et al. have successfully used this non-negligible symmetric helical exchange interaction to explain the weak ferromagnetism of La2CuO4. By using the non-Markovian quantum state diffusion method, the quantum discord of non-Markovian dynamics in the spin chain system that has Kaplan–Shekhtman–Entin-Wohlman–Aharony interactions and Dzyaloshinskii-Moriya interactions is studied. The effects of Kaplan–Shekhtman–Entin-Wohlman–Aharony interaction on the quantum discord under different external magnetic fields at zero and finite temperatures are discussed. The results show that the quantum discord in the system can be increased via the increasing of Kaplan–Shekhtman–Entin-Wohlman–Aharony interaction in the case of zero or uniform magnetic field, while the case is opposite under the nonuniform magnetic field. More importantly, the ideal discord state can be obtained by modulating the uniform magnetic field and Kaplan–Shekhtman–Entin-Wohlman–Aharony interaction. Moreover, the Markovian case and the effect of temperature on the quantum discord are also discussed, respectively.

Diamond has great potential applications in high-power, high-frequency semiconductor devices because of its wide band gap (5.5 eV), high thermal conductivity (22W/(cm·K)), and high carrier mobility (4500 cm2/(V·s) for electron, and 3800 cm2/(V·s) for hole). It has been widely considered as an ultimate semiconductor. From the analysis of our previous work, we find that the output current of field effect transistor based on hydrogen-terminated polycrystalline diamond is usually larger than that based on single crystal diamond, and that the preferential orientations of the polycrystalline diamond are mainly \begin{document}$ \langle 110\rangle $\end{document} and \begin{document}$ \langle 111\rangle $\end{document} shown by XRD results. Therefore, in order to further analyze the effect of surface orientation on the device performance of hydrogen-terminated diamond field effect transistor (FET), we study the devices fabricated respectively on the (110) plane and (111) plane single crystal diamond plates obtained from a single 3.5-mm-thick single crystal diamond grown by the microwave plasma chemical vapor deposition on the high-pressure high-temperature synthesized diamond substrate. Prior to processing the device, these diamond plates are characterized by atomic force microscope, Raman spectra and photoluminescence (PL) spectra. The results of Raman and PL spectra show that (110) plane and (111) plane plates originating from the same CVD single crystal diamond have no significant difference in optical property. Then the normally-on hydrogen-terminated diamond FET with a gate length of 6 μm is achieved. The device on (111) plane delivers a saturation drain current of 80.41 mA/mm at a gate voltage VGS = –4 V, which is approximately 1.4 times that of the device on (110) plane. Meanwhile, the on-resistance of the device on (111) plane is 48.51 Ω·mm, and it is only 67% of the device on (110) plane. Analyses of the capacitance-voltage show that the hole concentration of the gated device on (110) plane and (111) plane are 1.34 × 1013 cm–2 and 1.45 × 1013 cm–2, respectively, approximately at the same level. In addition, the hole density of the device on both (110) and (111) plane increase near-linearly with the increase of gate voltage from the threshold voltage to – 4 V, indicating that the control effect of the gate on the carrier in the channel is uniform. The possible reason for the higher saturation drain current as well as the lower on-resistance of the device on (111) plane is that its sheet resistance is lower.

A facile phosphine-promoted [2 + 3] cycloaddition of dialkyl azodicarboxylates with β,γ-unsaturated α-keto esters was developed, and a series of pyrazoline derivatives were obtained with good yields under mild conditions. Furthermore, the scope of the cyclizations was investigated.

Microflocs, which are the first-order aggregates of cohesive sediment, are formed during early-stage flocculation through random collisions in turbulent flow. This study proposes a numerical model to describe the non-equilibrium flocculation of cohesive sediments in homogeneous turbulent flows using the lattice Boltzmann method. The validity of the model is verified by analytical results. The influence of suspended sediment concentration and turbulence on the early-stage flocculation phenomena of cohesive sediments at the mesoscale is examined, and it is found that the number of microflocs increases with sediment concentration up to an optimum concentration of 2.0 kg/m^3, after which it decreases with sediment concentration. The mean settling velocities of the suspension sediments in the computational domain first increase with increasing shear rate, then decrease, and the optimum shear rate is approximately 17.6 s^-^1. Additionally, the turbulence-induced flocculation process can have an influence on the turbulent flow.

Diamond has a great potential to be used in high-power, high-voltage and high-frequency semiconductor devices due to its wide band gap (5.5 eV), high breakdown field (> 10 MV/cm), high thermal conductivity (22 W/(cm·K)), and good carrier transport property. High-quality polycrystal diamond with large size wafers (up to several inches) is more easily obtained than the expensive monocrystal diamond plate with the size of only several mm2, and the good performance of electronic device on polycrystal diamond has been reported. So we fabricate a normally-on hydrogen-terminated polycrystal diamond field effect transistor with a 4-μm aluminum gate by using a gold mask process. The saturation drain current is 160 mA/mm, and the on-resistance is as low as 37.85 Ω ·mm. The maximum transconductance reaches 32 mS/mm, and the gate voltage range with the transconductance higher than 90% of its maximum value reaches 3 V (-2 V ≤ VGS ≤ -5 V). An Ohmic contact resistance of 5.52 Ω ·mm and a quite low square resistance of 5.71 kΩ/sq for the hydrogen-terminated diamond are extracted from the analysis of transmission line model measurement. On the basis of the analyses of the obtained results, the on-resistance of device dependent on gate voltage, and the capacitance-voltage data measured at the gate-source diode, we find that the hole sheet density under the gate reaches 1.56×1013 cm-2 at a gate voltage of -5 V, and the extracted effective mobility of the holes stays at about 170 cm2/(V·s) in the afore-mentioned gate voltage range with high transconductance. In summary, the high and broad transconductance peak and the low on-resistance are attributed to the relatively low gate-source and gate-drain series resistance, the high-density carriers in the channel, and the high-level mobility achieved over a large gate voltage range. The relevant research of finding proper dielectrics for the gate insulator and the passivation layer is under way to further improve the device performance.

To reveal the internal physics of the low-temperature mobility of two-dimensional electron gas (2DEG) in Al-GaN/GaN heterostructures, we present a theoretical study of the strong dependence of 2DEG mobility on Al content and thickness of AlGaN barrier layer. The theoretical results are compared with one of the highest measured of 2DEG mobility reported for AlGaN/GaN heterostructures. The 2DEG mobility is modelled as a combined effect of the scattering mechanisms including acoustic deformation-potential, piezoelectric, ionized background donor, surface donor, dislocation, alloy disorder and interface roughness scattering. The analyses of the individual scattering processes show that the dominant scattering mechanisms are the alloy disorder scattering and the interface roughness scattering at low temperatures. The variation of 2DEG mobility with the barrier layer parameters results mainly from the change of 2DEG density and distribution. It is suggested that in AlGaN/GaN samples with a high Al content or a thick AlGaN layer, the interface roughness scattering may restrict the 2DEG mobility significantly, for the AlGaN/GaN interface roughness increases due to the stress accumulation in AlGaN layer.

The mobility of the two-dimensional electron gas (2DEG) in AlGaN/GaN hetero- structures changes significantly with Al content in the AlGaN barrier layer, while few mechanism analyses focus on it. Theoretical calculation and analysis of the 2DEG mobility in AlGaN/GaN heterostructures with varied Al content are carried out based on the recently reported experimental data. The 2DEG mobility is modeled analytically as the total effects of the scattering mechanisms including acoustic deformation-potential, piezoelectric, polar optic phonon, alloy disorder, interface roughness, dislocation and remote modulation doping scattering. We show that the increase of the 2DEG density, caused by the ascension of the Al content in the barrier layer, is a dominant factor that leads to the changes of the individual scat- tering processes. The change of the 2DEG mobility with Al content are mainly de- termined by the interface roughness scattering and the alloy disorder scattering at 77 K, and the polar optic phonon scattering and the interface roughness scattering at the room temperature. The calculated function of the interface roughness pa- rameters on the Al content shows that the stress caused AlGaN/GaN interface degradation at higher Al content is an important factor in the limitation of the in- terface roughness scattering on the 2DEG mobility in AlGaN/GaN heterostructures with high Al content.

Considering the problem generated by cyber attack threat on C4ISR system structure, a modeling and simulation method on C4ISR system structure effect based on statistical parameter of complex network is proposed. Firstly, the concept about C4ISR system structure effect is first presented, and two different structure effects are proposed: system structure damaged effect and structure efficiency reduction effect, Secondly, the cyber attack means faced by wired Network and battle wireless network are analyzed, then revealing the generation mechanism of system structure effect, and the system structure attack modeling is also established, Thridly, according to the system structure connectivity and running efficient, the math modeling is established on system structure effect based on connectivity rate, connectivity coefficient and information efficiency parameters. Finally, in the simulation environment, considering the area joint air defense combat command information system as the experiment object, the system structure effect test is developed according to set different attack strategy.

In the GaN-based heterostructures, this paper reports that the strong electric fields induced by polarization effects at the structure boundaries complicate the electric–static equilibrium and the boundary conditions. The basic requirements of electric–static equilibrium for the heterostructure systems are discussed first, and it is deduced that in the application of the coupled Schrodinger–Poisson model to the heterostructures of electric–static equilibrium state, zero external electric field guarantees the overall electric neutrality, and there is no need to introduce the charge balance equation. Then the relation between the screening of the polar charges in GaN-based heterostructures and the possible boundary conditions of the Poisson equation is analysed, it is shown that the various boundary conditions are equivalent to each other, and the surface charge, which can be used in studying the screening of the polar charges, can be precisely solved even if only the conduction band energy is correctly known at the surface. Finally, through the calculations on an AlGaN/GaN heterostructure with typical structure parameters by the coupled Schrodinger–Poisson model under the various boundary conditions, the correctness of the above analyses are validated.

It was reported by Shen et al that the two-dimensional electron gas (2DEG) in an AlGaN/AlN/GaN structure showed high density and improved mobility compared with an AlGaN/GaN structure, but the potential of the AlGaN/AlN/GaN structure needs further exploration. By the self-consistent solving of one-dimensional Schrodinger–Poisson equations, theoretical investigation is carried out about the effects of donor density (0–1×1019 cm−3) and temperature (50–500 K) on the electron systems in the AlGaN/AlN/GaN and AlGaN/GaN structures. It is found that in the former structure, since the effective ΔEc is larger, the efficiency with which the 2DEG absorbs the electrons originating from donor ionization is higher, the resistance to parallel conduction is stronger and the deterioration of 2DEG mobility is slower as the donor density rises. When temperature rises, the three-dimensional properties of the whole electron system become prominent for both of the structures, but the stability of 2DEG is higher in the former structure, which is also ascribed to the larger effective ΔEc. The Capacitance–Voltage (C−V) carrier density profiles at different temperatures are measured for two Schottky diodes on the considered heterostructure samples separately, showing obviously different 2DEG densities. And the temperature-dependent tendency of the experimental curves agrees well with our calculations.

Diamond has been considered as an ultimate semiconductor, which has great potential applications in high power, high frequency semiconductor devices. Up to now, the twodimensional hole gas (2DHG) induced on the hydrogenterminated diamond surface is used most popularly to form electric conduction in diamond semiconductor at room temperature, due to the obstacle caused by lacking of easily-ionized dopants. A 200-nm-thick single crystalline diamond is grown by microwave plasma chemical vapor deposition on the type-Ib high-pressure high-temperature synthesized diamond substrate. Then the sample is treated in hydrogen plasma atmosphere to achieve hydrogen terminated diamond surface. The sample is characterized by X-ray photoelectron spectroscopy and atomic force microscope. After that, the normally-on hydrogen-terminated diamond field effect transistors are achieved. The device with a gate length of 2 μup m delivers a saturation leakage current of 96 mA/mm at gate voltage VGS=-6 V, at which, however, the gate leakage current is too large. The saturation current reaches 77 mA/mm at VGS=-3.5 V with safety. The device shows typical long-channel behavior. The gate voltage varies almost linearly. In the saturation region of the device, the transconductance (gm) increases near-linearly to 30 mS/mm with the increase of the gate voltage in a range of 5.9 V. Analyses of the on-resistance and capacitance-voltage (C-V) data show that the 2DHG under the gate achieves a density as high as 1.99×1013 cm-2, and the extracted channel carrier density and mobility are always kept increasing with VGS negatively shifting to -2.5 V. The nearlinearly increasing of gm in a large VGS range is attributed to high 2DHG density, quite a large gate capacitance (good gate control), and increased mobility. The relevant researches of improving the carrier mobility in the channel and of finding proper gate dielectrics to improve the forward gate breakdown voltage are underway.