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In this work, we fabricated a vertical diamond Schottky barrier diode (SBD) with a high breakdown electric field of 4.8 MV/cm and a forward current density of 2361 A/cm2. Compared with a regular diamond SBD, the breakdown electric field of SBD with a HfO2 field plate (FP) increased from 183 to 302 V, the current swing (ION/IOFF) was on the order of 1011. As the thickness of the HfO2 FP increased from 200 to 400 nm, the breakdown voltage of the SBD increased from 280 to 314 V, and the corresponding breakdown electric field increased from 4.5 to 5 MV/cm. We also measured the current–voltage characteristics at different temperatures to investigate the cause of the high on-resistance. As the measured temperature increased from 25 to 150 °C, the on-resistance of the device decreased from 4.7 to 1.7 mΩ·cm2. By studying the interface between HfO2 and the diamond, we found that HfO2 can reduce the interface state density of the Schottky contact. The interface state density of Zr/HfO2/diamond was lower than 1.5 × 1013 eV−1·cm−2. This work provides a simple strategy for realizing high-performance diamond SBDs.

The normally-off Yttrium (Y) gate hydrogen-terminated (H-terminated) diamond field effect transistor (FET) with 5 nm Al2O3 dielectric layer has been successfully fabricated and evaluated in this work. The threshold voltage is extracted to be - 0.21 V at drain source voltage of −10 V, and the normally-off mode should be caused by the low work function of Y. The saturated drain current (IDSsat) is - 16.14 mA/mm obtained at gate voltage (VGS) of - 2.5 V with 4 μm gate length and 100 μm gate width. The value of I DSsat I DSmax is relatively high compared with other normally-off H-terminated diamond FETs at the same gate voltage, and this is ascribed to the well-preserved two-dimensional hole gas channel. The maximum transconductance of the fabricated device is 7.97 mS/mm. The current on/off ratio is about 7 orders of magnitude with a subthreshold swing of 150 mV/dec. The maximum effective mobility is 233.08 cm2/V. The results contribute to the development of normally-off H-terminated diamond FETs significantly.

For realizing the heterogeneous integration of semiconductor materials and overcoming the heat dissipation problem of GaN-based high-power semiconductor devices, Mo/Au interlayers were applied to realize the room temperature bonding between Si and Si, GaN and Si, GaN and diamond, GaN HEMTs and diamond wafers in atmospheric air. Low voidage and high bonding strength were achieved. In addition, the temperature distributions and thermal resistances of the devices bonded on different substrates (sapphire, Si, SiC and diamond) with Mo/Au interlayers were calculated by numerical simulation.

The nitrogen vacancy (NV) center distribution in epitaxial lateral overgrowth (ELO) single crystal diamond layer grown on tungsten patterned HPHT substrate by microwave plasma chemical vapor deposition (CVD) system has been investigated. It has been found that in ELO diamond layer densities of NV0 and NV− center above the tungsten metal are enhanced. Meanwhile, in patterned high-pressure and high-temperature (HPHT) substrate the density of NV− center beneath the tungsten metal is much higher than that of NV0. The HPHT substrate does not contain NV centers before CVD growth, and there is almost no NV center in the region without tungsten metal after growth.

We investigate the contribution of four-photon bunching term in fourth-order double-slit interference intensity correlation based on two different detection schemes with a pseudo-thermal light source. It is clearly demonstrated that the resolution of intensity correlation is significantly enhanced by using of double-slit in both fourth-order and third-order intensity correlation. Meanwhile, the visibility of fourth-order correlation can be dramatically improved in contrast to the third-order due to the four-photon bunching term by contributing in the visibility of fourth-order correlation. The position and full width at half maximum of interference peaks of fourth-order intensity correlation are same as third-order. We also use two different scanning approaches to change the resolution and visibility of interference intensity correlation. In the first detection scheme, we scan three reference detectors along the same orientation and speed. In second detection scheme we scan two of three reference detectors in the same orientation, and speed of one reference detector is twice that of the other, and simultaneously moving the other two reference detectors with opposite orientation but identical speed. Those investigations can also be promoted to high order intensity correlation of thermal light.

Fabrication of hydrogen-terminated diamond (H-diamond) field-effect transistor (FET) with AlOx dielectric layer has been successfully carried out. The AlOx layer was formed by auto-oxidizing 6 nm Al film in the air at room temperature, and a FET without AlOx dielectric layer has also been fabricated for comparison. For both FETs, 100 nm Al layers were deposited as the gate electrodes, respectively. The leakage current density in FET with AlOx dielectric layer was four magnitude orders lower than that without AlOx dielectric layer at VGS = −5 V, indicating that AlOx dielectric layer could effectively reduce leakage current and prevent reverse ID in ID − VDS caused by defects on diamond surface. Distinct pinch-off characteristic with p-type channel was observed in ID − VDS measurement. The threshold voltage was −0.4 V at VDS = −15 V.

Fabrication of dual-termination Schottky barrier diode (SBDDT) by using oxygen-/fluorine-terminated diamond (OT-/FT-diamond) has been carried out on P-/P+ diamond. X-ray photoelectron spectroscopy (XPS) measurement was used to determine the chemical composition of OT-/FT-diamond surface treated by ultraviolet ozone and C4F8 plasma, respectively. The barrier heights of Au on OT-/FT-diamond were calculated to be 2.0 ± 0.12 and 2.39 ± 0.12 eV, respectively. Au film was patterned on the OT-/FT-diamond as the schottky electrode, and Ti/Au film were deposited on the backside of substrate as ohmic electrode, then a SBDDT was achieved completely. SBDDT exhibits better forward and reverse I-V characteristics based on the optimum OT-/FT-diamond (WO/WF) area ratio 0.2, which illustrates that the combination of dual surface termination is an efficient way to optimize the performance of diamond SBD.

China power grid has the characteristics of long-distance transmission architecture and significant strong DC systems and weak AC systems pattern. This makes the converter commutation failure difficult to avoid, which may accelerate deterioration or even destroy the stability of the AC and DC systems. Recently, a novel security measure with additional large-capacity synchronous condenser (SC) has been proposed and installed in the AC support systems of multi-infeed Ultra-HVDC to ensure AC systems voltage stability and prevent commutation failures. This paper deduces the mechanism of SC to suppress commutation failure, compares and analyzes the advantages of SC compared with other reactive power compensation devices as well. According to the characteristics of multi-outfeed and multi-infeed Ultra-HVDC system, the electromagnetic model considering AC grid structure is constructed, and the role of SC in practical application system is simulated and tested. It is proved that this method can effectively reduce the number of consecutive commutation failures and shorten the commutation failure time, which can be widely applied to practical projects.

Fabrication of normally-off hydrogen-terminated diamond field-effect transistors (FET) has been carried out by using 3 nm Al2O3 dielectric layer, which was formed by thermally oxidizing 3 nm Al in air. 100 nm Al was covered on the 3 nm Al2O3 dielectric layer to form Al/Al2O3 gate. The leakage current density of FET with 6 μm gate length kept smaller than 5 × 10− 7 A·cm− 2, while the gate voltages swept from 3 to − 5 V. The capacitance-voltage characteristic indicated low-trapped charge densities in Al2O3 dielectric layer. For comparison, FET with only 3 nm Al2O3 gate and with 100 nm Al/3 nm Al2O3 gate was fabricated, which showed normally-on and normally-off characteristic respectively, indicating that 100 nm Al/3 nm Al2O3 gate could deplete hole densities in FET channel due to the difference of work function between Al and hydrogen-terminated diamond.

Enhancement of ultraviolet absorption through localized surface plasmon resonance (LSPR) was realized by assembling of Pd nanoparticles on homoepitaxial diamond thin films. The result of UV–vis spectrum of Pd nanoparticles embedded in diamond surface demonstrated the LSPR at wavelength of 213 nm, resulting in the improvement of ultraviolet absorption in diamond. The diamond ultraviolet photodetectors with and without Pd nanoparticles were fabricated and investigated. The results showed that the photoresponse from photodetector with Pd nanoparticles was 57.28 mA/W under 210 nm light at 5 V, which was three orders higher than that of detector without nanoparticles, and the UV/viable rejection ratio can reach to 4 orders of magnitude. This excellent performance should be attributed to LSPR in Pd nanoparticles, which was further confirmed by finite difference time domain (FDTD) simulation.

Submicron lenses and cylinders exhibiting excellent properties in photodetector and quantum applications have been fabricated on a diamond surface by an inductively-coupled plasma (ICP) etching technique. During ICP etching, a layer containing 500 nm diameter balls of SiO2 was employed as mask. By changing the mixing ratio of O2, Ar and CF4 during ICP etching, several submicron structures were fabricated, such as cylinders and lenses. The simulation results demonstrated that such submicron structures on a diamond&rsquo, s surface can greatly enhance the photon out-coupling efficiency of embedded nitrogen-vacancy center.

Fabrication of microlenses on a diamond surface is an important way to enhance the performance of the embedded nitrogen vacancy (NV) center which is a promising single light source for quantum communication and quantum-based detection. In this work, lenses with a micrometer diameter were fabricated on a diamond surface by using the inductively coupled plasma (ICP) etching technique with a mask of polystyrene (PS) balls. First, 1 µm diameter PS balls were dispersed on the surface of deionized water. Then, the balls were transferred onto a diamond surface. Third, the sample was treated using the ICP technique to form microlenses. By increasing ICP etching time, the surface of fabricated microlenses became smoother. The simulation results demonstrate that the microlenses can greatly improve the photon collection efficiency of the embedded NV center and focus more excitation light to the NV center than bulk diamond.

The light out-coupling efficiency of top-emitting OLED devices with different micro-structures was investigated with the aid of software FDTD solutions. The micro-structures included surface grating, wavy shape and spherical micro lens respectively. The simulation results indicated that the micro-structure was helpful to improve the light out-coupling efficient of OLED. Further more a complex spherical crown surface micro-structure was designed. The light out-coupling efficient of top-emitting OLED with the complex spherical surface improved 14% compared that of the device with smooth surface and 6% compared with micro lens.

We report the generation of three-mode hybrid intensity-noise correlation and intensity-difference squeezing of spontaneous parametric four-wave mixing (SP-FWM) and fourth-order fluorescence (FL) signals in the heteronuclear-like (three-level Λ-type) molecular structure of a Pr3+:Y2SiO5 (Pr3+:YSO) crystal using the nonlinear cross-Kerr effect under a polarized dressing effect. In the semi-classical view of a Kerr nonlinear medium, the amplitude of two-mode hybrid correlations of this kind is subject to a limit determined by the hybrid maximally entangled state. Whereas the degree of correlation and squeezing is determined by the dressing effects of the input laser fields participating in the SP-FWM process. We also find that the variations in magnitude of three-mode hybrid intensity-noise correlation and intensity-difference squeezing are consistent with nonlinear cross-Kerr processes. Such a three-mode hybrid signal may have potential applications in long-distance communication, dense coding, all-optical communication and quantum storage on photonic chips.

As one of the key elements of high-power laser systems, the pulse compression multilayer dielectric grating is required for broader band, higher diffraction efficiency and higher damage threshold. In this paper, the multilayer dielectric film and the multilayer dielectric gratings(MDG) were designed by eigen matrix and optimized with the help of generic algorithm and rigorous coupled wave method. The reflectivity was close to 100% and the bandwith were over 250nm, twice compared to the unoptimized film structure. The simulation software of standing wave field distribution within MDG was developed and the electric field of the MDG was calculated. And the key parameters which affected the electric field distribution were also studied.

In this study, diamond pseudo-vertical architecture Schottky barrier diodes (PVSBDs) through the patterning tungsten growth method have been investigated. The forward current density is 16 A/cm2 at 5 V, and a rectification ratio is more than 5 orders of magnitude at ±5 V for diamond PVSBD. The reverse breakdown voltage is 640 V, and the corresponding electrical field is 4.57 MV/cm. These results are obtained by patterning tungsten (W) on the diamond surface as a blocking layer and growing a diamond epitaxial layer on the uncovered zone. A W/diamond ohmic contact was formed during the diamond epitaxial layer growth process. An aluminum film was used as a Schottky contact. Overall, the results illustrate that W patterned growth to fabricate PVSBD is efficient.

In this study, a NiO/diamond UV-photodetector has been fabricated and investigated. A single crystal diamond (SCD) layer was grown on a high-pressure-high-temperature Ib-type diamond substrate by using a microwave plasma chemical vapor deposition system. NiO films were deposited directly by the reactive magnetron sputtering technique in a mixture gas of oxygen and argon onto the SCD layer. Gold films were patterned on NiO films as electrodes to form the metal-semiconductor-metal UV-photodetector which shows good repeatability and a 2 orders of magnitude UV/visible rejection ratio. Also, the NiO/diamond photodetector has a higher responsivity and a wider response range in contrast to a diamond photodetector.

The pulse compression multilayer dielectric grating (MDG) is one of the key elements of high-power laser systems. Mixed metal multilayer dielectric gratings(MMDG) with wider spectrum and higher diffraction efficiency are gradually becoming hot topic in chirped pulse compressor. In this paper, we studied the reflection and diffraction characteristics of pulse compression grating, i.e MMDG. First the thin-film structure, which would be applied to MMDG, was designed by combining characteristic matrix method and global optimization algorithm and the influence of the metal thickness and the number of layer film to reflectivity was also analyzed. Grating design software based on reflectivity vector theory (RCW)was developed to analyze the diffraction characteristic of MMDG. Combining generic algorithm and RCW, the optimization design of MMDG is studied. Comparing the diffraction efficiency of before and after optimization design, the highest diffraction efficiency is higher than 99% and bandwidth of MMDG is over 200nm, 50nm wider than that of MDG.

In this paper, we do some research on the interior period microstructure of transparent materials induced by a femtosecond laser of 800-nm wavelength. By adopting a nonlinear propagation physical model of femtosecond laser pulses and considering the spherical aberration effect(SA), we analyze the influence of nonlinear effects such an self-focusing, GDV, MPA, plasma defocusing and interface aberration on femtosecond laser propagation in transparent materials. Meantime, in the case with nonlinear effects and interface aberration, we research the influence of fs laser power, pulse width, numerical aperture and focusing depth on period microvoid. Simultaneously, compared with simulating results in different focusing lens numerical aperture, we find that big numerical aperature and deep focusing more easily produced period voids.

The broadband mid-IR grating is required in the infrared spectrophotometer to keep the instrument compact. In this paper the optimization design of a type of broadband grating is studied by the rigorous diffraction grating electromagnetic theory. As a differential vector method, the rigorous coupled wave analysis (RCWA) has been widely used for the analysis and the design of diffractive structures. In this paper, firstly, the diffraction efficiency properties of the traditional broadband dual-blaze grating were analyzed by RCWA. Then a simple structure grating with broadband spectrum can be obtained to the dual-blaze grating. It is interesting that the designed grating only had one blazed angle which is more easily to made compared to dual-blaze grating. The optimization grating structure parameters were given. According to our design example of broadband, mid-IR metal grating, the grating with grating period 10.0μm and blazed angle 22 degree can obtain more than 80% diffraction efficiency within the whole broadest spectrum 8~18μm. The optimization design result demonstrates this simple structure grating is with broadband spectrum and more easily to produce than the dual-blaze gratings.

DPL coupling system was researched in this paper. First, the mathematic model of 3D and 2D light transmission in hollow duct was analyzed and compared. Then the 3D simulation software for all rays of the coupling system -lens duct was developed. The influence of various structural parameters of the hollow lens duct to the energy and the beam distribution were discussed with the help of developed software. The structural parameters such as the duct length, the lens radius, the size of the input and output ends were researched and were optimized to get higher efficiency and better beam distribution. Finally, the energy conversion efficiency and the beam spatial distribution of before and after optimization were compared. The results showed that the efficiency and the distribution of energy were well improved after the optimization.

In this paper the rigorous coupled wave analysis (RCWA) was used to analyze the grating diffraction efficiency properties. First, the RCWA must to be improved to avoid instability when the grating period and grating groove depth are relatively large especially for TM mode incident wave. Then the global optimization method-genetic algorithm was used to optimize the grating profile to achieve high diffraction efficiency. Based on the improved RCWA the grating optimal design software(GODS) was developed with the aid of the genetic algorithms (GA). The optimized structure parameters of several typical grating profiles in arbitrary incident angle were given by GODS within short time once the optimal control parameters were selected.