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Single-photon emitters based on intrinsic defects in silicon carbide (SiC) are promising as solid-state qubits for the quantum information storage, whereas defect engineering in a controllable manner still remains challenging. Herein, the thermally-driven defect dynamic reaction in the ion implanted 4H-SiC has been exploited through the optical emission spectra of defects. For the heavy-ion (Si or Ar) implanted samples with abundant Frenkel pairs, the silicon vacancies (VSi) are energetically converted into the carbon antisite-vacancy pair (CSi-VC) upon annealing till 1300 °C for 30 min, accompanied with the gradual lattice recovery and local strain relaxation. The further temperature elevation dissociates the metastable CSi-VC into carbon antisite (CSi) and carbon vacancy (VC), as supported by the consequent quenching of the (CSi-VC)-related emission at 700 nm. Thus, the whole defect reaction is probed as the vacancy interconversion from VSi to VC with the byproduct of stacking faults. In contrast, the intermediate CSi-VC complexes are not energetically favorable during the annealing of the H-implanted sample, which results from the negligible generation of Frenkel pairs, as supported by the x-ray diffraction patterns and Raman scattering analysis. These findings provide guidance for defect engineering in SiC toward the creation of reliable single photon emitters.

At present, field grinding measurement devices are mainly adopted for DC synthetic electric field measurement. The sensor unit of the device is of a rotating blade structure, and the surface wind generated by rotation causes ion flow distortion, making it difficult to ensure the accuracy of measurement data. In order to optimize the sensing structure of measuring equipment, the vibration-type synthetic field sensing mode was obtained through selection analysis, the horizontal vibration sensor structure and data acquisition hardware circuit structure were proposed, and a vibration-type synthetic field measuring prototype was developed. Through the simulation comparison of the influence of vibration type and field grinding type on the electric field, it can be known that the internal field intensity of the upper and lower 1 mm planes of the equipment shell is basically uniform, and the field intensity of the square and the corner position of the equipment shell are distorted. The electric field distortion of the upper surface of the field grinding device and vibration device is 2.36-8.55 and 1.9-6.84, respectively. The higher the device is, the greater the distortion of the field intensity near the shell, and the distortion of the field grinding type is larger than that of the vibration type. Vibration equipment has less influence on the background field intensity when measuring the ground composite field intensity.

The morphologies of dislocation etch pits and dislocation deflections of on-axis 4H-SiC substrate etched by molten KOH were observed with the help of a microscope. Based on experimental observation and etch mechanism, a method for the identification of threading edge dislocations, threading screw dislocations (TSDs) and threading mixed dislocations was proposed. The details about the inner micro-structure of threading edge dislocations and TSDs were observed by laser scanning confocal microscope and scanning electron microscopy. The morphologies and the cross-sectional views of the basal plane dislocation formed by threading edge dislocation were observed and two models were formed to explain it.

We have studied the field-effect carrier transport of graphene on 4H silicon carbide substrate. In order to extract the electrical parameters, the top-gated field effect transistor has been fabricated. By fitting the measured results with Kim’s model, the field effect carrier mobility (µ) and the metal/graphene contact resistance (Rc) and the residual carrier concentration (n0) are derived to be 3382cm2/Vs, 2250Ω▪µm and 2.18×1013cm-2, respectively. It is noted that the large contact resistance did not affect the high field effect carrier mobility of our device. The high carrier mobility suggests that the SiC epitaxial graphene may be quite suitable for the future high speed electronic applications.

State-of-the-art AlGaN/GaN high electron mobility structures were grown on semi-insulating 4H-SiC substrates by MOCVD and X-band microwave power high electron mobility transistors were fabricated and characterized. Hall mobility of 2291.1 cm2/(V·s) and two-dimensional electron gas density of 9.954 × 1012 cm–2 were achieved at 300 K. The HEMT devices with a 0.45-μm gate length exhibited maximum drain current density as high as 1039.6 mA/mm and peak extrinsic transconductance of 229.7 mS/mm. The f T of 30.89 GHz and f max of 38.71 GHz were measured on the device. Load-pull measurements were performed and analyzed under (–3.5, 28) V, (–3.5, 34) V and (–3.5, 40) V gate/drain direct current bias in class-AB, respectively. The uncooled device showed high linear power gain of 17.04 dB and high power-added efficiency of 50.56% at 8 GHz when drain biased at (–3.5, 28) V. In addition, when drain biased at (–3.5, 40) V, the device exhibited a saturation output power density up to 6.21 W/mm at 8 GHz, with a power gain of 11.94 dB and a power-added efficiency of 39.56%. Furthermore, the low f max/f T ratio and the variation of the power sweep of the device at 8 GHz with drain bias voltage were analyzed.

N–B co-doped SiC, as an excellent candidate for white LEDs, were prepared by the physical vapor transport growth method. Doping type and concentrations of fluorescent SiC crystals were examined by Raman spectroscopy and secondary ion mass spectroscopy measurements. The band-to-band excitation mechanism of donor and acceptor pairs (DAPs) luminescence in f-SiC has been clarified based on excitation spectroscopic measurements. The luminescence intensity of DAPs decreases with the increase of excitation source energy due to the absorption when excitation source energy is greater than 3.7 eV. Moreover, the threshold energy and the optimal excitation wavelength did not change with the carrier concentration, while the photoluminescence emission intensity increased with the decrease of carrier concentration. When the excitation power increased from 2 to 44 mW, the luminescence intensity can be well fitted by the power dependence I = aP γ , the higher the B doping concentration, that is, the lower the carrier concentration, the intensity is more sensitive to the excitation power change. At same time, the luminescence peaks of high doping concentration samples shift to the high energy with high excitation power. The shifts and the underlying mechanism have been discussed.

The control of blue Smoke in coal-fired power plants is of great significance to the atmospheric environment. The emission of SO3 from coal-fired power plants is an important factor of blue Smoke production, which mainly comes from boiler combustion and selective catalytic reduction (SCR) denitration. When the content of SO3 in the flue gas is too high, it will cause problems such as dust accumulation, low-temperature acid corrosion, increased air preheater resistance, and degraded performance of the electric precipitator, which will affect the economical efficiency and safety of the unit. In this paper, the causes of blue Smoke in coal-fired power plants are analyzed, the conversion rate of SO3 is calculated and verified, and technical measures to control colored plumes are proposed.

The development of thermal power units in China is restricted. In the process of transformation, coupled biomass power generation is the main direction of the transformation in the fuel sides. This paper introduces the constraints of thermal power units, the main ways of coal-fired coupling power generation, the technical route of coupling biomass in all of 84 pilot thermal power units and the problems faced by coupled biomass power generation. On this basis, some suggestions on the application of coal-fired coupling power generation in enterprises are put forward.

After the ultra-low emission reform of the coal-fired power plant, the ammonia slip at the outlet of the Selective Catalytic Reduction(SCR) denitrification device increases, resulting in abnormal air preheater resistance, which affects the economic and safety of the unit. The optimized adjustment test was carried out on the ammonia injection system of the SCR denitration device for 600 MW coal-fired unit. Under the premise of meeting the ultra-low emission of the unit, the NOx and ammonia escape at the outlet of the denitration device are controlled by adjusting the ammonia injection manual door to reduce the NOx distribution deviation of the outlet. The test shows that the standard deviation of the NO concentration distribution at the outlet of the reactor A reduced from 27.72% before adjustment to 12.53% after adjustment. The standard deviation of the NO concentration distribution at the outlet side B decreased from 55.78% before adjustment to 14.52% after adjustment. The uniformity of the NOx distribution in the outlet zone of the reactor is significantly improved, thereby effectively controlling the escape of ammonia.

In recent years, convolutional neural networks have attracted much attention due to their powerful image feature learning capabilities. However, in many cases, the network exhibits shortcomings such as difficulty in training and adjustment, and time-consuming training. This paper combines clustering and constrained Boltzmann machines to propose a multi-scale feature mapping method based on clustering convolution. Experiments were carried out on Cifar-10 and lung X-ray images. This method not only shortened the time but also improved the accuracy. Therefore, the proposed method is superior to the traditional feature extraction method.

Yb3+ : NaGd(WO4)2 single crystal with dimensions O30 × 60 mm2 has been grown by the Czochralski method. XRPD experimental results show that the as-grown Yb3+ : NaGd(WO4)2 crystal belongs to the tetragonal system and the I41/a space group. The high crystalline quality of the as-grown Yb3+ : NaGd(WO4)2 crystals was confirmed by HRXRD. The effective segregation coefficient of the Yb element in Yb3+ : NaGd(WO4)2 crystal growth was measured to be 0.812 using the x-ray fluorescence method. Subsequently, the thermal properties were systematically studied by measuring the thermal expansion, specific heat and thermal diffusion coefficients. The density of the as-grown Yb3+ : NaGd(WO4)2 crystal at 22 °C was measured by using the buoyancy method with a resulting value of 7.143 g cm−3 and almost linearly decreases as the temperature increases due to the thermal expansion. Comparing the thermal properties of several tungstate crystals, we find that the Yb3+ : NaGd(WO4)2 crystal possesses relatively larger anisotropic thermal expansion and specific heat but smaller thermal conductivity than those of other tungstate crystals.

A 1.3 µm passively Q-switched Nd:KLu(WO4)2 laser under direct 880 nm pumping is reported. Graphene on a silicon carbide is used as the saturable absorber. Stable Q-switched laser pulses are obtained at the central wavelength of 1355.3 nm. Under an absorbed pump power of 14 W, the average output power, pulse repetition rate and single pulse energy are 890 mW, 135 kHz, and 6.6 µJ, respectively.

We reported graphene as a passive Q-switcher in a neodymium-doped lutetium vanadate (Nd:LuVO4) crystal laser. The maximum average output power, pulse repetition rate, and pulse width were 474 mW, 795 kHz, and 56.2 ns, respectively, with the graphene used as the passive Q-switcher by using its saturable absorbing property and with its substrate SiC used as the output coupler by using its high refractive index. Our results illustrate the feasibility of using graphene as a Q-switcher for solid-state lasers.