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Magnetic pole erosion is a key life-limiting factor of low-power Hall thrusters. In this study, the effects of the magnetic field intensity near the inner magnetic pole on the pole erosion of a 100 W permanent-magnet Hall thruster at rated operating point were investigated using magnetic field intensity adjustment technology. The experimental results indicate that the erosion rate of the inner magnetic pole decreased considerably with a decrease in the magnetic field intensity near the inner magnetic pole, and the erosion rate can be decreased by over 37.5% when the magnetic field intensity decreased by 20%. Further analysis indicates that the decrease of magnetic field intensity reduces the number of electrons moving along the magnetic field lines to the magnetic pole, and increases the surface potential of the magnetic pole. The reduction of the potential difference between the channel outlet and the magnetic pole leads to a decrease in the current density and energy of the ions sputtered to the magnetic pole, which contributes greatly to the decrease in pole erosion rate. This study provides a reference for the protection of magnetic pole erosion.

A subwavelength asymmetric grating refractive index (RI) sensor based on quasi-bound states in the continuum (q-BIC) with temperature self-compensation was proposed. The sensor structure consisted of a prism/asymmetric grating/analytes, where the grating layers were periodically arranged asymmetric silicon (Si) and polydimethylsiloxane. The asymmetry of the structure led to the fact that the tangential field component and the radiative field component in the grating layer were no longer in a fully decoupled state at the resonance position, creating two extremely narrow q-BIC resonance peaks, which gave the sensor a high figure of merit (FOM) and a low detection limit (DL). In addition, the thermo-optical coefficient of the materials made one of the resonance peaks more sensitive to temperature changes, realizing the temperature self-compensation of RI detection and thus improving the detection accuracy. From the results, reducing the asymmetry of the structure by modifying the parameters could theoretically make FOM > 5.1 × 106 RIU−1 and DL < 9.8 × 10−9 RIU. For the RI sensor with temperature self-compensation, FOM = 3057.85 RIU−1 and DL = 1.64 × 10−5 RIU for the RI, FOM = 0.88 °C−1 and DL = 0.057 °C for the temperature. These findings could effectively improve the temperature interference resistance of the sensor and thus the accuracy of trace substance detection.

Semiconductor mode-locked lasers (MLLs) with extremely high repetition rates are promising optical frequency comb (OFC) sources for their usage as compact, high-efficiency, and low-cost light sources in high-speed dense wavelength-division multiplexing transmissions. The fully exploited conventional C- and L- bands require the research on O-band to fulfil the transmission capacity of the current photonic networks. In this work, we present a passive two-section InAs/InGaAs quantum-dot (QD) MLL-based OFC with a fundamental repetition rate of ∼100 GHz operating at O-band wavelength range. The specially designed device favours the generation of nearly Fourier-transform-limited pulses in the entire test range by only pumping the gain section while with the absorber unbiased. The typical integrated relative intensity noise of the whole spectrum and a single tone are −152 and −137 dB Hz−1 in the range of 100 MHz–10 GHz, respectively. Back-to-back data transmissions for seven selected tones have been realised by employing a 64 Gbaud four-level pulse amplitude modulation format. The demonstrated performance shows the feasibility of the InAs QD MLLs as a simple structure, easy operation, and low power consumption OFC sources for high-speed fibre-optic communications.

An axisymmetric two-phase lattice Boltzmann method is adopted to simulate the dewetting dynamics of the liquid film on a substrate fabricated with different types of roughness: pillar-type, nail-type and mushroom-type. The liquid film remains in the Wenzel or half-Wenzel state. The dewetting of the liquid film occurs after generating an initial dry spot on the substrate and forming a contact line between the liquid film, gases and the substrate. The dewetting is characterized by the continuous size growth of the contact line’s radius. The effect of the geometric factors of the roughnesses on the dewetting dynamics is analyzed in detail. For the pillar-type roughness, three dewetting modes, named ‘no residual,’ ‘part residual’ and ‘full residual’, are identified, and a mode map that depends on the geometrical factors is given. For the nail-type roughness, the dewetting process is found to be clearly restrained. For the mushroom-type roughness, only the ‘full residual’ mode is found, and the depth of the grooves hardly affects the dewetting speed, if the liquid film remains in the Wenzel state; but if it remains in the half-Wenzel state, the liquids would be brought out completely from the grooves and thus result in a faster dewetting speed under smaller penetration of the liquid film. The results indicate that the different geometric elements of the roughness could affect the dewetting speed to different degrees. Determining how the structured roughness affects the dewetting speed can help the industry control the dewetting process of the liquid film.

In this study, high performance amorphous In–Ga–Zn–O (a-IGZO) TFTs were successfully fabricated with inkjet-printed silver source-drain electrodes. The results showed that increased channel thickness has an improving trend in the properties of TFTs due to the decreased contact resistance. Compared with sputtered silver TFTs, devices with printed silver electrodes were more sensitive to the thickness of active layer. Furthermore, the devices with optimized active layer showed high performances with a maximum saturation mobility of 8.73 cm2 V−1 S−1 and an average saturation mobility of 6.97 cm2 V−1 S−1, I on/I off ratio more than 107 and subthreshold swing of 0.28 V/decade, which were comparable with the analogous devices with sputtered electrodes.

x-cut Nd : MgO : LiNbO3 wafers are implanted with 3 MeV O+ ions at a dose of 6 × 1014 cm−2, directly using a photoresist mask consisting of a series of open stripes of width 10 µm. The extraordinary refractive index (RI) experiences positive changes with respect to the bulk after ion bombardment and post-implantation annealing; therefore, channel waveguide structures are formed in the implanted regions. The near field intensity distributions of the transverse-electric modes are obtained by an end-fire coupling arrangement. The modal simulation result shows the reasonableness of the reconstructed RI profiles, which is helpful in designing practical waveguide devices produced by the ion implantation technique.

Double waveguides were produced in potassium titanyl phosphate (KTiOPO4 or KTP) by ion exchange in pure RbNO3 at 340 °C for 45 min, and subsequently ion implantation with 500 keV O ions at a dose of 1 × 1015 ions cm−2. By the prism-coupling method the guided mode spectra as well as the refractive index profiles of the ion-exchanged sample were determined. The relative value of the refractive index distribution of the ion implanted KTP sample in the z direction was simulated, which indicates the formation of double waveguides. The field pattern of the propagation light in the waveguide was collected and studied by the end-coupling method. The near-field pattern of two planar operating waveguides was observed, one upon the other. The irradiation damage as well as the Rb distribution was analysed by means of the Rutherford backscattering spectrometry technique.

We report the structural evolution of diamond films in a plasma assisted hot filament chemical vapour deposition system with a variable substrate bias through a two-step process including deposition and subsequent modification. It is found that the diamond surfaces can be significantly modified after the treatment of hydrogen plasma. The surfaces with pyramidic structures form under the proper treated duration and temperature with a decrease in the content of amorphous carbon. As the treatment is prolonged, the surface presents ellipsoid structures while the diamond film becomes amorphous. Furthermore, 50 µm-long columns appear instead of the ellipsoids in a higher regime of the substrate temperature. These results suggest that the hydrogen plasma treatment and substrate temperature can significantly tune the surface topography of diamond films, and even give rise to chemical bonding variations with pronounced surface structures.

The main objective of this investigation is to examine the effects of a new technique, double-ageing, on the microstructure and mechanical properties of the ultrahigh strength steel Aermet 100. Under the condition of double-ageing, there is no apparent decrease in the steel strength. However, the impact fatigue life can be prolonged by 35.5% and the dynamic fracture toughness raised by 22.6% by this technique compared with normal ageing. Based on the observation of the microscopic structure, the physical mechanism of prolongation of fatigue life and enhancement of the stability of the reverted austenite is analysed further. The results show that this new technique is a breakthrough in optimally combining the strength and toughness of Aermet 100 steel. In light of the current understanding of this subject, the toughness of the reverted austenite formed at the time of heat preservation at the higher temperature of the double-ageing process increases drastically. Moreover, during the treatment at the lower temperature of the double-ageing process, the carbon separating from the martensitic ferrite of Aermet 100 steel will diffuse into the reverted austenite, resulting in a decrease of the brittleness of the martensite and an increase of the stability of the reverted austenite.

In discharge processes, electrode erosion is inevitable and may be a primary cause of gap failure. Features generated from electrode erosion, such as particulates and pits, would lead to field distortion and self-breakdown failure, in essence. To quantitatively clarify how these features of erosion are generated as the discharge shot accumulates, this paper introduces a statistical method to analyze particulate concentration in the eroded surface. Based on experimental data from laser confocal microscopy, this method could extract and process the profile of the electrode surface after different discharge shots. Statistical results indicate that conditioning effects have been found in the first 100 shots, where the discharge arc plays a role to polish more prominently, rather than ablate, the electrode surface. After this period, electrode erosion could be found to be increasingly heavier and the number of particulates and pits increases rapidly. The proportion function of the particulates height or pits depth can be fitted by power distribution and the correlations between the two function coefficients a, b and discharge shots number n are roughly linear, positive and negative, respectively.

Traditional methods to evaluate the quality of amorphous silicon-substituted tin oxide (a-STO) semiconductor film are destructive and time-consuming. Here, a novel non-destructive, quick, and facile method named microwave photoconductivity decay (μ-PCD) is utilized to evaluate the quality of a-STO film for back channel etch (BCE) thin-film transistors (TFTs) by simply measuring the D value and peak reflectivity signal. Through the μ-PCD method, both optimum deposition procedure and optimal annealing temperature are attained to prepare a-STO film with superior quality. The a-STO TFTs are fabricated by the obtained optimum procedure that exhibits a mobility of 8.14 cm2 V−1 s−1, a I on/I off ratio of 6.07 × 109, a V on of -1.2 V, a steep subthreshold swing of 0.21 V/decade, a low trap density (D t) of 1.68 × 1012 eV−1 cm−2, and good stability under the positive/negative gate-bias stress. Moreover, the validity of the μ-PCD measurement for a-STO films is verified by x-ray photoelectron spectroscopy, Hall effect measurement, and the performance of STO TFTs measured by traditional methods. The non-destructive μ-PCD method sheds light on the fast optimization of the deposition procedure for amorphous oxide semiconductor films with excellent quality.

A simple analytic expression for the pressure of a two-dimensional Yukawa liquid is found by fitting results from a molecular dynamics simulation. The results verify that the pressure can be written as the sum of a potential term which is a simple multiple of the Coulomb potential energy at a distance of the Wigner–Seitz radius, and a kinetic term which is a multiple of the one for an ideal gas. Dimensionless coefficients for each of these terms are found empirically, by fitting. The resulting analytic expression, with its empirically determined coefficients, is plotted as isochores, or curves of constant area. These results should be applicable to monolayer dusty plasmas.

GaInNAs materials with narrow bandgaps of 1.10 eV have been grown on a Ge substrate by metalorganic chemical vapor deposition to fabricate GaInNAs/Ge (1.10/0.67 eV) double-junction solar cells. We have studied the photovoltaic characteristics and the external quantum efficiencies of the double-junction cells with various annealing conditions and different GaInNAs base layer thicknesses. The best external quantum efficiency is obtained from the double-junction cell with a 1170 nm thick GaInNAs base layer annealed at 675 °C for 30 min. Under AM1.5G illumination, the best double-junction cell has a short circuit current density (J SC) as 23.63 mA cm−2, which is dominated by the J SC of the GaInNAs subcell.

Photoluminescence quantum efficiency and energy transfer were studied in ErRE (RE = Y, Yb) silicate thin films. For the first time, we experimentally determined the radiative/non-radiative decay rates of ErYb and ErY silicates and obtained photoluminescence quantum efficiencies of 0.28 ± 0.08 and 0.39 ± 0.13, respectively. Energy transfer between Yb and Er in ErYb silicate was investigated by comparing the effective excitation cross sections of ErYb and ErY silicate. At different pumping wavelengths, forward and backward energy transfer caused by the presence of Yb was experimentally demonstrated.

Thin-film transistors (TFTs) using indium zinc oxide as the active layer and anodic aluminium oxide (Al2O3) as the gate dielectric layer were fabricated. The device showed an electron mobility of as high as 10.1 cm2 V−1 s−1, an on/off current ratio of as high as ∼108, and a turn-on voltage (V on) of only −0.5 V. Furthermore, this kind of TFTs was very stable under positive bias illumination stress. However, when the device experienced negative bias illumination stress, the threshold voltage shifted to the positive direction. It was found that the instability under negative bias illumination stress (NBIS) was due to the electrons from the Al gate trapping into the Al2O3 dielectric when exposed to the illuminated light. Using a stacked structure of Al2O3/SiO2 dielectrics, the device became more stable under NBIS.

Two emission peaks were observed in the low temperature photoluminescence (LTPL) spectra of an InGaN/GaN multiple quantum well (MQW) structure before and after nanopillar fabrication. After nanopillar fabrication it is found that among the two peaks the longer wavelength peak exhibits a clear blue shift and has a much stronger enhancement in LTPL intensity than the shorter one. Combined with x-ray diffraction and spatially resolved cathodoluminescence analyses, the difference induced by nanopillar fabrication is ascribed to different strain relaxation states in the lower and upper quantum well layers. It is found that the lower QW layers of the as-grown MQW which causes the longer wavelength PL peak are more strained, while the upper ones are almost fully strain-relaxed. Therefore, the nanopillar fabrication induces much less strain relaxation in the upper part of the MQW than in the lower one.

Planar optical waveguides were formed in ZnO crystal by Tm+ and O+ ion implantation. The distributions of Tm+ in as-implanted and annealed ZnO samples were investigated by the RBS technique. A shift of the Tm+ peak towards the sample surface and out diffusion were observed after thermal treatment and subsequent O+ ion implantation. Waveguide formation was determined after O+ implantation in Tm+-implanted ZnO crystal. By using the prism-coupling method two guided modes were detected. The refractive index profile in the implanted waveguide was reconstructed according to the SRIM and RCM simulation. The RBS/channelling measurements show that the lattice structure of ZnO did not suffer detectable damage after O+ implantation.

Multiferroic composite ceramics of (1 − x)[0.94Bi0.5Na0.5TiO3–0.06BaTiO3]–xCoFe2O4 (BBNTO–CFOx), x = 0.1, 0.2, 0.3, 0.4, 0.5, have been prepared and their structure, magnetoelectric (ME) effect, magnetic and ferroelectric properties have been investigated. x-ray diffraction and scanning electron microscopy show that the ceramics consist of separated perovskite BBNTO and spinel CFO. The ME effect is revealed by measuring the magnetic hysteresis loops of the same sample before and after electric poling. The magnetization increases gradually with increasing CFO content. Further electric measurements reveal that BBNTO–CFO0.30 has the largest polarization with a remanent polarization of 60.9 µC cm−2, which is even larger than that of pure BBNTO. The enhanced ferroelectricity might be ascribed to the ME effect. Our results may be helpful for developing new lead-free multiferroic composites with improved properties.

Defects play a key role in the determination of material properties, especially at small scales. The influence of several kinds of defects (point vacancies, line vacancies and cracks) on the deformation and fracture characteristics of a planar copper grain boundary interface with a 45° lattice misorientation is explored using molecular dynamics simulations and the embedded-atom method. Both tensile and shear modes of interfacial separation are considered. The results show that the crystalline defects can have a strong influence on the interfacial behaviours. The sensitivity of the mechanical properties of the interface to a defect type may be different under tension than under shear. It is found that some defect topologies can improve certain properties (e.g. strength and fracture strain) of the bicrystal interface system.

We fabricated a white organic light-emitting diode (WOLED) by hybrid emissive layers which combined phosphorescence with fluorescence. In this device, the thin layer of 4-(dicyanomethylene)-2-(t-butyl)-6-(1, 1, 7, 7-tetramethyljulolidyl-9-enyl)-4H-pyran played the role of undoped red emissive layer which was inserted between two blue phosphorescence emissive layers. The blue phosphorescent dye was bis[(4, 6-difluorophenyl)-pyridinato-N, C2] (picolinato) Ir(III), which was doped in the host material, N, N'-dicarbazolyl-1, 4-dimethene-benzene. The WOLED showed stable Commission Internationale de L'Eclairage coordinates and a high efficency of 9.6 cd A−1 when the current density was 1.8 A m−2. The maximum luminance of the device achieved was 17 400 cd m−2 when the current density was 3000 A m−2.

We report on the formation of reconfigurable optical channel waveguides (including straight stripes and Y-branches) on top of iron-doped lithium niobate crystals. The sample surface is first implanted by 500 keV protons to form a planar waveguide showing a propagation loss of ~1.6 dB cm−1 after modest post-implantation annealing. Afterwards, the sample surface is illuminated with well-defined stripe patterns (straight channels, beam splitters) of green light using lithographic masks. Due to the photovoltaic effect in lithium niobate resulting in negative index changes in illuminated regions, waveguide layers are formed in the non-illuminated regions perpendicular to the planar waveguide in the same way as it occurs in the dark spatial soliton regime. In this way two-dimensional waveguides are formed in the overlap region on top of the crystal that may be used for reconfigurable optical interconnections and splitters.

We study the electronic structure and magnetic properties of equilibrated and distorted Co2MnSi1−xAlx using density-functional theory calculations. We find that equilibrated Co2MnSi shows true half-metallicity while Co2MnAl shows traditional ferromagnetism. The tensile stress deteriorates the half-metallicity of Co2MnSi, while it induces a transition from traditional ferromagnetism to true half-metallicity for Co2MnAl. The intermediate Co2MnSi1−xAlx alloys show compromise properties between pure Co2MnSi and Co2MnAl. Detailed studies show that the stretch stress enhances the splitting of the t2g orbital while it has little influence on the eg orbital for all Co2MnSi1−xAlx alloys. Finally, we deduced that graded heterostructural Co2MnSi1−xAlx alloys with Co2MnAl side epitaxial growth on silicon would keep high temperature half-metallicity throughout the heterostructure to the interface, and this may be a scheme to fulfil efficient spin injection into silicon.

Well-separated silicon nanoparticles (Si-NPs) were deposited on Si wafer and amorphous carbon micro-grids at room temperature by magnetron sputtering through a nanocluster source. With the introduction of He as a carrier gas in Ar sputtering atmosphere, well-separated Si-NPs with narrow size distribution can be observed by transmission electron microscopy. High resolution transmission electron microscopy study reveals that the average size of the Si-NPs is about 5 nm in diameter. Furthermore, well-crystallized Si-NPs without oxidized layer are of strong photoluminescence with a double-peak structure at the positions of 380 and 398 nm at room temperature.