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We have demonstrated performance-improved vertical diamond Schottky barrier diode (SBD) by introducing a lanthanum hexaboride (LaB6) interfacial layer between Zr and diamond. The composition of LaB6 was characterized using X-ray photoelectron spectroscopy. The fabricated diamond SBD with LaB6 delivers a rectification ratio of $10^{{10}}$ , a Schottky barrier height (SBH) of 1.53 eV, a saturation current density of $1.82\times 10^{-{19}}$ A/cm2, and a shunt resistance of $2.67\times 10^{{12}} \,\,\Omega $ . These results indicate that with the inclusion of LaB6, diamond SBD exhibits improved SBH and reverse breakdown capability. Additionally, the trap-limited space-charge-limited current (SCLC) remains the determinant transport mechanism for diamond SBD with LaB6. Meanwhile, the interface states density is significantly reduced due to the effect of LaB6. These results suggest the great potential of vertical Zr/LaB6/p-diamond SBD as future high-performance power rectifiers.

In this communication, we propose a novel method to electrochemically modify hydrogen-terminated diamond surface in MISFETs with LiF dielectric at room temperature. The chemical reaction is 2F- + C–H+2h+→C–F + HF. According to measurement results of X-ray photoelectron spectroscopy on diamond, C–F bonds were produced after electrochemistry modification. A model was proposed to explain the electrochemistry modification on MISFETs. In this model, the theoretical electrolysis voltage of F− was calculated to be −3.8V, which was consistent with the experimental value of -5V.

A normally OFF hydrogen-terminated diamond (H-terminated diamond) field-effect transistor (FET) has been successfully achieved with Ti/TiO x gate materials. A 5-nm Ti film was deposited on H-terminated diamond by electron beam evaporation technique and then it was thermally oxidized in air at 120 °C for 10 h to form Ti/TiO x , which was confirmed by X-ray photoelectron spectroscopy. The threshold voltage of H-terminated diamond FET is −0.14 V at ${V}_{DS}$ of −8 V, indicating a normally OFF operation. The normally OFF property could be attributed to the difference of work difference between Ti and H-terminated diamond, which may deplete the hole carriers in H-terminated diamond 2-D hole gas (2DHG) conduction channel. The maximum mobility of H-terminated diamond FET is 313 cm2/Vs at ${V}_{GS}$ of −0.2 V. And, the fixed negative charge density is $3.37 \times 10 _{11}$ cm−2. The results demonstrate that Ti/TiO x H-terminated diamond FET is a good solution to fabricate normally OFF device with a simple fabrication process, undamaged 2DHG channel, and uncontaminated interface between Ti and TiO x gate materials, which may promote the development of normally OFF H-terminated diamond FET.

Fabrication of single crystal hydrogen-terminated diamond MOSFET with dielectrics of LiF/Al2O3 has been successfully carried out. After patterning source and drain electrodes, 60nm LiF/ 20nm Al2O3 were deposited as dielectrics. The output and transfer characteristics were investigated, indicating the typical p-type channel MOSFET. The on/off ratio was $\sim 10^{{9}}$ , which was high enough for practical applications. The fixed and trapped charge in LiF/Al2O3 were also examined. Based on the capacitance-voltage curves, the dielectric constant of LiF/Al2O3 was calculated to be 36.1, which was ascribed to the LiF supercapacitor structure. To the best of our knowledge, this LiF supercapacitor structure was first used in hydrogen-terminated diamond MOSFET to improve the dielectric constant.

An enhancement-mode hydrogen-terminated diamond field-effect transistor (FET) is realized by using a low work function gate material, namely, lanthanum hexaboride (LaB6). The reason for the enhancement mode should be that the electrons in the LaB6 layer flow into the two-dimensional hole gas (2DHG) channel and compensate the holes, such that the channel is shut down. The threshold voltages ( ${\mathrm {V}}_{\text {TH}}$ ) range from − 0.29 V to − 0.72 V with different gate lengths. The device with 2 $\mu \text{m}$ gate length shows a − 57.9 mA/mm maximum drain current density ( ${\mathrm {I}}_{\text {DSmax}}$ ) at ${\mathrm {V}}_{\text {GS}} =-$ 5 V. The on/off ratio is around 9 orders of magnitude, with a subthreshold swing of 130 mV. Effective mobility ( $\mu _{\text {eff}}$ ) as high as 195.4 cm2/ $\text{V}\cdot \text{s}$ is obtained from the device. This technique reveals undamaged 2 DHG characteristics, uncontaminated interface between LaB6 and aluminum gate metal, and a simple fabrication process, which will promote the development of enhancement diamond FETs.

We introduce a simple method with thermal annealing round gold disk for agglomeration to fabricate orderly arranged nanostructure arrays on diamond for single photon source applications. In the annealing process, the dependence of gold sphere size on disk thickness and diameter was investigated, showing that gold sphere diameter was decreased with decreasing gold disk thickness or diameter. The condition parameters of ICP etch were adjusted to obtain different nanostructure morphologies on diamond. The collection efficiency of nitrogen-vacancy (NV) center embedded in nanostructure as-fabricated could reach to 53.56% compared with that of 19.10% in planar case with the same simulation method.

In this paper, we successfully synthesized homoepitaxial diamond with high quality and atomically flat surface by microwave plasma chemical vapor deposition. The sample presents a growth rate of 3 μm/h, the lowest RMS of 0.573 nm, and the narrowest XRD FWHM of 31.32 arcsec. An effect analysis was also applied to discuss the influence of methane concentration on the diamond substrates.

Localized surface plasmon-enhanced diamond UV photodetectors with different Ir nanoisland arrays had been successfully fabricated. Three different Ir nanoisland arrays with the diameters of 20(D20), 30(D30) and 40(D40) nm were deposited on the diamond surface, respectively, and their height was 10 nm. Ti/Au metal electrodes were patterned on Ir nanoisland arrays area and bare diamond surface to form UV photodetectors. According to photoelectric performance test results, the responsivities of diamond photodetectors with Ir nanoislands were far greater than that of diamond photodetector, and the D40 showed the highest photocurrent and responsivity at 210 nm, and the D20 indicated the highest UV/vis rejection ratio. The results of simulated extinction spectra exhibited three resonance peaks at UV and visible region for each sample, indicating that D20 had the highest ratio of UV/vis, which was coincide with experiment results.

Investigation of influence of floating metal rings (FMRs) edge termination technique on the breakdown voltages of diamond Schottky barrier diodes (SBDs) has been carried out. Unintentionally doped P- drift layer was grown on HPHT boron doped diamond substrate by microwave plasma CVD system and treated by ultraviolet ozone. Then, Ti/Ni/Au electrode was deposited on the back side of the substrate to form ohmic contact. Zr/Ni/Au Schottky electrodes with different FMRs parameters, such as ring spacing (RS), ring width (RW) and ring number (RN), were deposited on the P- layer. The I–V measurement results show that breakdown voltages increase firstly and then decease with increasing of RS. The increases of RW and RN are beneficial to improve breakdown voltages. Moreover, FMRs structure can effectively improve breakdown voltages without deteriorating forward current density and rectification ratio of diamond SBDs.

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.

Direct determination of barrier height (ΦBH) value between Ir and single crystal (001) hydrogen-terminated diamond with lightly boron doped has been performed using x-ray photoelectron spectroscopy technique. 70 nm Ir islands were formed on hydrogen-terminated diamond surface using anodic aluminum oxide. The ΦBH value for lr/hydrogen-terminated diamond was -0.43 ± 0.14 eV, indicating that Ir was a suitable metal for ohmic contact with hydrogen-terminated diamond. The band diagram of lr/hydrogen-terminated diamond was obtained. The experimental ΦBH was compared with the theoretical ΦBH in this work.

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.

Boron implanted edge terminations have been demonstrated to enhance the breakdown voltages and stabilities of diamond Schottky barrier diodes (SBDs). The edge terminations were achieved by boron implant to form nonconductive amorphous regions under the edges of the Schottky contacts. Direct current measurements show the implanted regions did not contribute to the forward currents and high current densities of about 4000 A/cm2 were obtained at −5 V. By using boron implanted edge terminations, although an increase in leakage currents was observed, the average breakdown voltage of the devices was significantly improved from 79 V to 125 V, which is increased by more than 50%. In addition, the breakdown voltages of the devices without edge terminations degraded quickly after each repeating measurement, whereas the devices with edge terminations became much more stable and no obvious drop in breakdown voltages was observed.

In this study, we report ultraviolet photoresponse enhancement of diamond photodetector by applying patterned diamond film design and two-step growth process. Diamond stripes are fabricated on the surface and interdigitated electrodes are set perpendicular to them. Before second step growth, surface defects induced during etching process affect the responsivity of supra-band gap light. After second step growth, the surface defects are suppressed, then the responsivity of photodetector on diamond strips are larger than that of photodetector on continuous diamond film. The larger responsivity could be attributed to the quasi-one-dimensional carrier transport and large surface to volume ratio. In additionally, a large electrode space is helpful in enhancing ultraviolet photoresponse while suppressing the visible response.

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.

Interface fracture often occurs in systems of soft substrate and hard coatings during the service process, which is related to the weak interface strength and the unstable expansion of cracks along the interface induced by the residual thermal stress. The residual thermal stress mainly comes from the mismatch of thermal physical properties between matrix and hard coatings. In this study, a gradient carburized layer was prepared on TC4 substrate before the deposition of TiN(Ti) coatings using double glow plasma carburization. And then the mono- and multilayer TiN(Ti) coatings were synthesized on the carburized layer, forming composite hard coatings. The effect of substrate carburizing on properties of coatings was studied. The results show that the composite coatings' hardness can be increased nearly 2 times and the bonding strength is enhanced to over 80 N, compared with that of mono-and multilayer TiN(Ti) coatings. Also the interface brittle fracture tendency is restrained obviously by the hardened substrate, and the coordinative deformation ability of the coating at extra load is optimized. The composite coating composed of pre-carburized layer and TiN hard coating shows a higher strength and toughness.

The electrical properties, surface morphology and interface characteristics of W/p-diamond contact before and after annealing have been investigated. It is shown that the as-fabricated W/p-diamond contact exhibited non-linear behavior. After annealing at a temperature higher than 400 °C, the W/p-diamond contact showed ohmic behaviour. The specific contact resistance of W/p-diamond was 8.2 × 10−4 Ω·cm2 after annealing at 500 °C for 3 min in a N2 ambient, which was extracted from fitting the I-V relationship of TLM. It is noted that the RMS roughness increases with the annealing temperature increasing, which could be ascribed to the formation of WOX by the reaction of W and oxygen at high temperature. The XPS measurement showed that the barrier height of the W/p-diamond is 0.45 ± 0.12 eV after annealing at 500 °C. Furthermore, the formation of defects at the W/p-diamond interface, probably created by the formation of tungsten carbide during rapid thermal annealing, should be responsible for the ohmic formation of W/p-diamond after annealing at high temperature.

Epitaxial lateral overgrowth (ELO) of diamond films on patterned Ir/(0 0 1)HPHT-diamond substrates have been carried out by microwave plasma CVD system. Ir/(0 0 1)HPHT-diamond substrates are fabricated by photolithographic and magnetron sputtering technique. The morphology of the as grown ELO diamond film is characterized by optical microscopy and scanning electronic microscopy. The quality and stress of the ELO diamond film are investigated by surface etching pit density and micro-Raman spectroscopy. Two ultraviolet photodetectors are fabricated on ELO diamond area and non-ELO diamond area prepared on same substrate, and that one on ELO diamond area indicates better photoelectric properties. All results indicate quality of ELO diamond film is improved.

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.

A diamond-based field effect transistor with LaB6/Al2O3 bilayer has been fabricated. Al2O3 and LaB6 layer were deposited by atomic-layer-deposition and electron beam evaporation system, respectively. The LaB6/Al2O3 bilayer shows a high dielectric constant (29.8). The leakage current density of LaB6/Al2O3 diamond metal-insulator-semiconductor field effect transistor keeps lower than 1 × 10−6 A cm−2 when the gate bias changed from 5 V to −5 V. This device operates in a p-type depletion mode, whose maximum drain-source current, threshold voltage, maximum transconductance, effective mobility and sheet hole density are determined to be −73.8 mA·mm−1, 2.2 V, 10.4 mS·mm−1,128 cm2·V−1·s−1, and 3.2 × 1013 cm−2, respectively.

Homoepitaxial growth of step-flow single crystal diamond was performed by microwave plasma chemical vapor deposition system on high-pressure high-temperature diamond substrate. A coarse surface morphology with isolated particles was firstly deposited on diamond substrate as an interlayer under hillock growth model. Then, the growth model was changed to step-flow growth model for growing step-flow single crystal diamond layer on this hillock interlayer. Furthermore, the surface morphology evolution, cross-section and surface microstructure, and crystal quality of grown diamond were evaluated by scanning electron microscopy, high-resolution transmission electron microcopy, and Raman and photoluminescence spectroscopy. It was found that the surface morphology varied with deposition time under step-flow growth parameters. The cross-section topography exhibited obvious inhomogeneity in crystal structure. Additionally, the diamond growth mechanism from the microscopic point of view was revealed to illustrate the morphological and structural evolution.

To better stabilize the hydrogen-terminated surface, a diamond based metal-insulator-semiconductor field-effect transistor with Zr-Si-N dielectric layer has been investigated. On the diamond epitaxial layer grown by microwave plasma chemical vapor deposition system, Pd films were patterned as the source and drain electrodes by photolithography and electron beam evaporation methods. Then, a Zr-Si-N dielectric layer and W metal film were fabricated as the gate structure by radio frequency magnetron sputtering technique. The device illustrates p-type depletion mode, in which the threshold voltage, maximum transconductance, drain current maximum, capacitance and dielectric constant were calculated to be 3.0V, 1.27mS/mm, -5.16 mA/mm, 0.275μF/cm2 and 7.8, respectively. The result suggest that Zr-Si-N dielectric layer is shown to have the ability to protect the two-dimensional hole gas.

Metal nitride hard coatings, such as TiN and TiAlN are widely used to protect materials because of their higher hardness and wear properties. However, these coatings always contain a high degree of internal stress which could arouse adhesion problems. It is hard to synthesize monolayer TiN or TiAlN coatings thicker than 10 μm by PVD (physical vapor deposition). The multilayer composite structure, offering efficient means of controlling residual stress, is a successful way to synthesize thicker hard coatings. In the present study, a series of multilayer composite Ti/TiN coatings with different composite periods were synthesized by plasma enhanced ion plating and the effects of multilayered structure mechanical properties of the coating was studied. The result shows that the mechanical properties of the coating are strengthened with increasing the periods of composite Ti/TiN layer. The micro hardness (HV0.25) can reach to about 27 500 MPa and better toughness and higher thickness (≥50 μm) are obtained. The toughness of the coating is almost directly proportional to hardness. Meanwhile, the tribological performance of the coating is improved with a lower dry friction coefficient (about 0.35) and higher wear resistance by alternating 48 periods of Ti/TiN layer. However, the bonding strength of the coating is weakened with further increasing the period of Ti/TiN layer due to the weak interface of coating and substrate.

In this study, a biomimetic compound eye (BCE) was realized on diamond by combining thermal reflow with dry etching techniques. Firstly, photoresist pillars were developed on diamond surface by standard photolithography. Then, these pillars were reflowed on a hotplate to form spherical segment patterns. Furthermore, dry etching technique was used to transfer these patterns into diamond surface to form the convex curve surface with diameter of 300 μm, on which, ommatidia with diameter of 18 μm and space of 35 μm were fabricated with the same processes to obtain BCE. Finally, the as-fabricated diamond BCE was characterized, indicating a well-uniformity according to the point spread function and exhibiting clear images of the testing pattern in projection experiment, which is expected to work under harsh conditions such as high intensity irradiation and strong acid.

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.

In this work, we investigate the influence of defect concentration of the diamond substrates on the performance of hydrogen-terminated diamond field-effect transistors by Raman spectra, pulsed I–V characteristics analysis, and radio frequency performances measurements. It is found that a sample with higher defect concentration shows larger drain-lag effect and lower large-signal output power density. Defects in the diamond act as traps in the carrier transport and have a considerable influence on the large-signal output power density of diamond field-effect transistors. This work should be helpful for further performance improvement of the microwave power diamond devices.

Purpose Taking a 2,000 r/min 10 kW permanent magnet motor as an example, the purpose of this paper is to study the influence of driving modes on the performance of permanent magnet motor at limit conditions, and researched the variation mechanism of motor performance influenced by different driving modes. Design/methodology/approach A two-dimensional electromagnetic field model of the permanent magnet motor was established, and a rectangular-wave driving circuit was built. By using the finite element method, the electromagnetic field, current, harmonic content and eddy current loss were calculated when the motor operated at rated load and limit load. On the basis of the motor loss calculation, the temperature field of the motor operating at rated condition and limit condition was researched, and the factors that influence motor limit overload capacity were analyzed. By analyzing the motor loss variation at different load conditions, the change mechanism of the motor temperature field was determined further. Combined with the related experiments, the correctness of the above analysis was verified. Findings Permanent magnet synchronous motor (PMSM) driven by sine wave is better compared with brushless direct current motor (BLDCM) driven by rectangular wave in reducing the magnetic field harmonics, motor losses and optimizing the temperature distribution in the motor. The method driven by sine wave could improve the motor output performance including the motor efficiency and the motor overload capacity. The winding temperature is the most important factor that limits the output capability of PMSM operating for a long time. However, because of the large rotor eddy current losses, the permanent magnet temperature is the most important factor that limits the output capability of BLDCM operating for a long time. Practical implications The influence of driving modes on the motor magnetic field, losses and temperature distribution, efficiency and overload capacity was determined, and the influence mechanism was also analyzed. Combined with the analysis of the electromagnetic and temperature fields, the advantages of different driving modes were presented. This study could provide an important basis for the design of permanent magnet motors with different driving modes, and it also provides reference for the application of permanent magnet motor. Originality/value This paper presents the influence of driving modes on permanent magnet motors. The limit output capacity of the motor with different driving modes was studied, and the key factors limiting the motor output capability were obtained.

Localized surface plasmon-enhanced diamond UV photodetectors with different diameters of Pd nanoparticles (NPs) had been successfully fabricated. Four Pd NPs with diameters of 20, 40, 60, 70 nm were deposited on diamond surfaces, respectively, and their height was 20 nm. Ti/Ni/Au metal electrodes were patterned on samples surfaces to form UV photodetectors. According to photoelectric performance test results, responsivities were enhanced with sizes of particles increasing at UV region, and diamond photodetector with 40 nm NPs showed the highest photocurrent-to-dark current ratio and UV-to-visible rejection ratio. Compared with pure diamond photodetectors, the responsivity and UV/visible rejection ratio Pd modified detectors can improve up to 3250 and 34 times, respectively. Plasmonic scattering effect was used to explain this phenomenon, and it is further confirmed by the simulated scattering cross-section.

In this study, we fabricated and studied metal-oxide-semiconductor field effect transistors (MOSFETs) using bilayer Yb2TiO5/Al2O3 dielectrics on single crystal hydrogen-terminated diamond (H-diamond). Dielectric materials Yb2TiO5 and Al2O3 were deposited on H-diamond surface using radio frequency sputtering and atomic layer deposition, respectively. We point out that leakage current and hysteresis shift voltage of bilayer dielectric were three order of magnitude lower and one-third that of single layer Al2O3 dielectric, respectively. Based on capacitance-voltage characteristics dielectric constant, trapped charges and carrier hole density were evaluated for SD-Yb2TiO5/ALD-Al2O3 and ALD-Al2O3 MOSFET's. The effective mobility for Yb2TiO5/Al2O3 sample evaluated by using the relation between on-state resistance and 1/|VGS-VTH|was 102.4 cm2.V−1.s−1.

In this study, nitrogen-vacancy center emissions from nanocone structures fabricated on diamond surfaces by gold film annealing and inductively coupled plasma etching techniques were characterized. First, the diamond substate deposited with gold film was annealed to form a nano-sized dot mask. Second, through inductively coupled plasma etching, nanocone-shaped structures were fabricated using optimized gold dots as masks. Finally, the as-fabricated nanocone and planar structures were investigated with photoluminescence experiments at temperatures ranging from room temperature to 80 K, with the results showing approximately two-fold higher emission values for nitrogen-vacancy centers from nanocones.

The fabrication of a single-crystal hydrogen-terminated diamond metal-oxide-semiconductor field-effect transistor (MOSFET) with HfSiON/Al2O3 bilayer dielectric has been carried out. HfSiON and Al2O3 layers were deposited by sputtering-deposition (SD) and atomic layer deposition (ALD) techniques. The maximum output current for SD-HfSiON/ALD-Al2O3 was 36 mA mm−1, and for ALD-Al2O3, it was 31 mA mm−1. We reported that the hysteresis shift voltage of the bilayer dielectric MOSFET was one fourth of the single dielectric layer MOSFET. The leakage current density of SD-HfSiON/ALD-Al2O3 was one order of magnitude lower than the single layer dielectric. We also determined the dielectric constants of HfSiON/Al2O3 and Al2O3 dielectrics based on capacitance–voltage characteristics. The values of VTH, on/off ratio, subthreshold swing, and low field mobility for the bilayer dielectric MOSFET were evaluated to be 4.5 V, 105, 296 mV/decade, and 154 cm2 V−1 s−1, respectively.

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.

In this study, a Ti–diamond–Ti structured ultraviolet photodetector was fabricated on a homoepitaxial diamond layer with an oxygen-terminated surface. The properties of the Ti/diamond schottky contact were measured using X-ray photoelectron spectroscopy, and the barrier height was found to be 1.15 eV. At a bias of 3 V, the responsivity at 210 nm was only 4.29 mA/W, while at 12 V, the responsivity increased rapidly to 51 mA/W. The increase can be ascribed to the photocurrent gain. With the further increase in voltage, an avalanche effect was produced, and the responsivity could reach 1.18 A/W at 50 V. Moreover, the transient response behavior of the photodetector exhibited a good repeatability and response speed.

A growth of single crystal diamond (SCD) microchannels on HPHT diamond substrate has been carried out successfully by a simple and novel method. Firstly, aluminum film was patterned on SCD diamond substrate surface by magnetron sputtering, photolithography and dry etching techniques. Secondly, the aluminum patterns were transferred onto diamond substrate via inductively coupled plasma etching to form grooves on diamond surface. Finally, microchannels were achieved by epitaxial lateral overgrowth of SCD on the surface of prepared substrate by microwave plasma chemical vapor deposition system. After that, fluorescent liquid was introduced to check hollowness of the microchannels. This work provides a simple and time saving method to fabricate SCD microchannels for microfluidic system, which offers a great potential for hard environment applications.

A hundreds of microns three-dimensional single crystal diamond (SCD) channel along with high aspect ratio has been fabricated successfully by two-step process. Firstly, laser machining technique was used to produce trenches in high-temperature high-pressure SCD substrate. Then, microchannels were achieved by epitaxial lateral overgrowth of diamond layer on patterned substrate by microwave plasma chemical vapor deposition system. Dimensional variations and crystalline quality around the microchannel cross section were analyzed using scanning electron microscopy and Raman spectroscopy. The hollowness and continuity of microchannels were also be tested. It is a significant step towards fabrication of hundreds of microns SCD channel along with controlled high aspect ratio by a simple and controllable way.

Fabrication of single crystal hydrogen-terminated diamond MOSFET with YSZ/Al2O3 bilayer dielectrics has been successfully carried out. The flat band voltage shift and hysteresis voltage were small in the capacitance-voltage curve. The dielectric constant of YSZ/Al2O3 was calculated, and the fixed and trapped charge densities in dielectrics were deduced based on the capacitance-voltage curve. According to the transfer characteristics curve, on/off ratio and breakdown voltage were extracted. Distinct pinch-off and p-type channel were shown in the output characteristics curve. The effective mobility was evaluated to be 80.4 cm2 V−1 s−1 at VGS = −1.5 V based on the relation between on-state resistance and 1/|VGS-VTH|.

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.

In this paper, the creep behavior of P92 steel has been analyzed by creep strain and creep rate variations after the creep tests were stopped at the steady-state creep stage. The microstructure evolution of the P92 steel at the steady-state stage during creep test at 873 K under different load stresses of 125–160 MPa were studied by using a scanning electron microscopy (SEM) and a transmission electron microscopy (TEM). The grain boundary characteristics in the P92 steels during creep test were investigated by an electron backscattered diffraction (EBSD) technique. Experimental results showed that with increasing load stresses from 125 MPa to 160 MPa, creep rates of the P92 steels increased in Norton’s power law relation and creep times to the steady-state creep stage decreased. With decreasing load stresses and increasing creep times, martensite lath microstructure occurred recovery and the dislocation densities in ferritic matrix decreased. M23C6 particles located in prior austenite grain, sub-grain and lath boundaries showed slight coarsening. Some Laves phase particles precipitated in the grain boundaries for the P92 specimens after creep test under a load stress of 125 MPa. Comparing to as-tempered P92 steel, the volume fractions of LAGBs are lower and the volume fraction of HAGBs are higher with decreasing load stresses and increasing creep times. It is considered that understanding on creep behavior and microstructual evolution of the P92 steels during creep test will effectively support life design and assessment of the high temperature metal parts in fossil-fired power plant.

A low cost and networkable CO/sub 2/ monitor is developed, which consists of a non-dispersive infrared (NDIR) sensor and a network interface. It measures the CO/sub 2/ concentration by spectrum absorption in the 4.26 /spl mu/m band due to CO/sub 2/ molecules in the air. On-line calibration, the access to the TEDSs defined in IEEE 1451.2 standard and measured data are made by Java applet and client programs in C language. The prototype monitor has durability and long term stability with a measurement accuracy of /spl plusmn/(30ppm+2%) over the CO/sub 2/ concentration range from 380 ppm to 5000 ppm.

A temperature and relative humidity (RH) monitor using a thermistor and a polyimide-film RH sensor is developed for global assessment of thermal environments. The smart transducer interface module includes the relaxation oscillators for signal conditioning and a one-chip 16-bit microcomputer for networking. The microcomputer accommodates the calibration tables as well as the mandatory transducer electronic data sheets specified by the IEEE 1451.2 standard. The online calibration using the calibration table and the ratiometric signal conditioning allow /spl plusmn/0.14/spl deg/C accuracy over the temperature range from -20/spl deg/C to 50/spl deg/C and /spl plusmn/2.5RH accuracy over the RH range from 20%RH to 90%RH. Beside these high-accuracy measurements using low-cost sensors, the monitor features an adaptive architecture for global networking.