Table of contents

Low-temperature plasma plays various roles in industrial material processing as well as provides a number of scientific targets, both from theoretical and experimental points of view. Such rich features in variety are based on its complexities, arising from diverse parameters in constituent gas-phase species, working gas pressure, input energy density, and spatial boundaries. When we consider causalities in these complexities, direct application of machine-learning methods is not always possible since levels of complexities are so high in comparison with other scientific research targets. To overcome this difficulty, progresses in plasma diagnostics and data acquisition systems are inevitable, and the handling of a large number of data elements is one of the key issues for this purpose. In this topical review, we summarize previous and current achievements of visualization, acquisition, and analysis methods for complex plasma datasets which may open a scientific and technological category mixed with rapid machine-learning advancements and their relevant outcomes. Although these research trends are ongoing, many reports published so far have already convinced us of various expanding aspects of low-temperature plasma leading to the potential for scientific progress as well as developments of intellectual design in industrial plasma processes.

We report the absence of auxeticity in CoFe₂O₄, a magnetic spinel oxide. A CoFe₂O₄(111) epilayer was grown on the ZnO sacrificial layer, and the in-plane and out-of-plane lattice parameters were precisely determined by X-ray reciprocal space maps. To block the influence from stoichiometry variations, the same CoFe₂O₄ epilayer was lifted off from the substrate and was used as the reference sample. No auxetic behavior was found, and a positive Poisson ratio of ∼0.32 was obtained. Moreover, the Poisson ratio derived from the compliance coefficients agrees well with our experimental observation.

A method to grow GeSn nanodots has been developed by magnetron sputtering using anodic aluminum oxide as a template. With a high substrate temperature and a high deposition rate, flattened hill-like GeSn nanodots with high Sn content have been successfully formed directly on Ge(001) and Si(001) substrates. The GeSn nanodots are polycrystalline on Si and monocrystalline on Ge without Sn segregation. High-resolution transmission electron microscopy observations revealed that GeSn nanodots formed on Ge had a perfect interface without misfit dislocations.

In this study, a carbon-ion beam irradiation method with energy of 6.0 MeV was employed to prepare single-mode optical waveguide structures in LiF single crystal. The results of this study reveal that the visible light and near-infrared laser beams can be well-confined in the irradiated region that is influenced by the irradiation fluences. An end-face coupling system was used to estimate the propagation loss (1.3 dB cm⁻¹) after annealing treatment. The surface damage of the irradiated regions in LiF was analysed based on the displacements per atom calculation using the stopping and range of ions in matter code.

In this paper, we focus on the phase noise in optically-pumped magnetometer systems and investigate its sources, and use dual-phase lock-in technique to solve the problem. The results show that the phase noise is maximum when the system operates under zero-magnetic-field condition, and the main source comes from the environment stray magnetic field. The dual-phase lock-in technique improves the phase noise rejection by a factor of 10 compared to the single-phase lock-in technique. The sensitivity of the system is 22 fT Hz^−1/2 and the bandwidth is 158 Hz, which offers a favorable outlook for use in clinical settings.

After several repetitions of GaN epitaxial growth, the quality of the AlN template grown by metal–organic chemical vapor deposition deteriorated seriously, even when grown under the same procedure. However, the quality of the AlN template recovered a little the second time. It is found that this deterioration was enhanced if we increase the growth temperature. And this deterioration can be effectively weakened by omitting the baking procedure to cover the reactor chamber with AlN. The full width at half maximum of the X-ray rocking curve for AlN(102) significantly decreased from 1843 to 402 arcsec. This suggests that this deterioration of AlN quality is caused by residual gallium in the reactor chamber.

An ultra-narrow-band perfect absorber based on collective resonances in an Ag nanoring period array is theoretically proposed for the absorption enhancement of monolayer graphene, where the absorptivity can reach as high as 99.4% with the full-width-half-maximum as narrow as 3.6 nm in the visible band. This outstanding absorptive characteristic can be attributed to the excitation of surface lattice resonance modes by Ag nanoring periodic array. The as-designed structure possesses high refractive-index sensitivity, reaching 557.9 nm RIU⁻¹ with its figure of merit attaining 155 RIU⁻¹. This work provides promising guidance for developing high-performance graphene-based photonic devices.

Compact dual-band and tri-band bandpass filters (BPFs) based on high-order modes of spoof surface plasmon polaritons (SSPPs) are proposed. By using the meander line technique, the electrical size of the proposed SSPP structure was reduced by 68% compared with the traditional rectangular-grating SSPP structure. The high-efficiency passbands are excited by high-order modes of SSPPs. Therefore, dual-band and tri-band BPFs are designed by using two and three high-order modes of SSPPs, respectively. In addition, a notched band is obtained by loading three complementary split-ring resonators (CSRRs) on the bottom layer of the tri-band BPF. Thus, a quad-band BPF is achieved.

In this study, we investigated the modulation of the spin–orbit torque (SOT) caused by inserting the NiO layer at the Pt/Co interface. A similar Pt/NiO/Co structure was deposited on two different substrates, Al₂O₃ and Si/SiO_x substrates. We found that the damping-like torque of the Al₂O₃ type sample is almost independent of NiO thickness (t_NiO) when t_NiO < 2 nm, while that of Si/SiO_x type monotonically decreased with increasing t_NiO. The X-ray diffraction measurement revealed that the degree of interface roughness varies between these types. This suggests that the effect of the NiO insertion on the SOT is associated with the interface roughness.

One critical issue hindering high-quality, high-speed growth of GaN is cluster formation in the gas phase. We investigated cluster formation in tri-halide vapor phase epitaxial growth of GaN. The growth system is equipped with an external GaCl₃ gas supply system. We observed cluster formation under certain growth conditions experimentally. A simulation was also carried out to reveal the critical conditions for cluster formation. We propose that increasing the gas temperature is an effective way to suppress cluster formation, and thus achieve a higher growth rate with a flat surface morphology.

We report highly thermal-stable organic light-emitting diodes (OLEDs) by introducing an interfacial modification layer (IML), consisting of the N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine (NPB):MoO₃ bulk heterojunction. The IML can increase the thermal resistance of 4,4'-cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine] (TAPC) hole transport layer to be higher than its glass transition temperature. The OLED with the IML can endure a high temperature of 100 °C with a current efficiency of 51.82 cd A⁻¹ and a low-efficiency roll-off. The optimized thermal stability of OLED is not only due to the thermally stable IML but also resulted from the well-matched energy level between anode and TAPC with the help of IML.

The effects of heavy ion irradiation on the electrical response of HfO₂-based ferroelectric capacitors have been studied. All the hysteresis loops measured from the irradiated samples shifted toward the positive voltage. The remanent polarization and relative permittivity of the capacitors decrease with increasing ion fluence. The leakage current exhibit negligible change after irradiation. The main reason causing the phenomena is swift heavy ions (SHIs) induced the pinning of domain walls, attributed to the phase transition. This work provides the possible physical mechanisms of SHIs irradiation on HfO₂-based ferroelectrics, which is of significance for the space application of HfO₂-based ferroelectric random access memory.

Chiral antiferromagnets are regarded as a new class of antiferromagnets owing to its intriguing spin transport properties such as a sizable anomalous Hall effect (AHE). In this work, we fabricated chiral antiferromagnetic L1₂-Mn₃Ir (111)-oriented films and investigated the anomalous Hall conductivity with respect to the chemical order parameter $S.$ It is found that the anomalous Hall conductivity in (111)-oriented films is much more pronounced compared to (001)-oriented films, which is consistent with the theoretical prediction. We also found that the anomalous Hall conductivity strongly depends on the longitudinal conductivity, which could suggest an extrinsic contribution to the AHE in L1₂-Mn₃Ir.

Exploration of the phase transition is one of the hottest topics in condensed matter physics. In this paper, we have fabricated 2H-MoTe₂ devices and investigated their magnetotransport properties. As temperature decreases, the 2H-MoTe₂ flake undergoes several metal–insulator transitions, including insulator-to-metal transitions at ∼143 K and ∼36 K, respectively, and metal-to-insulator transitions at ∼109 K. In addition, these transitions are not affected by the application of external magnetic fields. The possible physical mechanisms behind these intriguing transitions originate from the electron–phonon coupling and the impurity scattering in the 2H-MoTe₂ flakes.

In this letter, the top-gate dual-active-layer TFT has been fabricated by in situ deposition of oxygen-rich ultrathin In-Sn-O layer on a top of the In-Ga-Zn-O (IGZO) active layer in order to suppress the hysteresis and improve negative bias illumination stability. The oxygen-rich ultrathin In-Sn-O layer can effectively reduce the oxygen vacancies concentration of the semiconductor layer from 33.16 to 1.13%. The decrease of oxygen vacancies indicates that the trap density and electron trapping are reduced, resulting in a reduced hysteresis from 0.66 to 0.02 V. Simultaneously, the negative bias illumination stability has been effectively improved from −0.89 to −0.29 V.

Absolute measurements of small-angle X-ray scattering (SAXS) intensities at the K absorption edge of Mg have been performed using glassy carbon as an intensity standard. Glassy carbon samples polished down to give appropriate transmission have been prepared as a secondary standard to be used at 1.3 keV. Al–Mg binary alloys were used to assess the metastable phase boundary for the Al₃Mg metastable precipitation from the absolute scattering intensity. The assessed phase boundary agreed with the previous reports. Glassy carbon was concluded to be an appropriate candidate for an intensity standard sample for transmission measurements of SAXS in the tender X-ray regions.

The fundamental electrical properties of undoped and Sb-induced Cu₂SnS₃ (CTS) thin films were evaluated. Furthermore, the relationship between defect properties during intentional degradation and thin film/solar cell properties was investigated. The carrier concentration decreased after Sb induction in the CTS film, and the resistivity increased by one order of magnitude. These values were independent of the Sb volume. These results imply that a small quantity of Sb atoms passivates the defects, such as Sb atoms at Sn or Cu sites that compensate for the intrinsic acceptors at Cu vacancies. In addition, the number of defects around the grain boundary tended to decrease with Sb induction because of passivation. The carrier concentration of the CTS layer remained unchanged following proton irradiation at 1 × 10¹⁴ cm⁻². Furthermore, the number of defects increased, independent of the Sb induction.

In this study, electrospun microfibers (MFs) were produced and used as key materials to optimize the composite with liquid crystal (LC) for terahertz (THz) wave phase shifters. These MFs, with an average diameter of 1.4 μm, were produced using the polymer solution concentration of 14 wt% and spinning voltage of 13 kV. When MFs were combined with LC, the measured results of the electrical characteristics showed that 14 wt% MFs provided an outstanding solution to the problem of a significant reduction in the natural birefringence of pure LC. The birefringence in the THz frequency range of the composite using 14 wt% MFs approached 90% compared with that using pure LC. Additionally, the decay time drastically shortened from hundreds of seconds for pure LC to hundreds of milliseconds for MF/LC composite and was independent of device thickness.

We investigated the optical properties of nanoscale WS₂ monolayers treated with organic solvents. The photoluminescence spectra changed significantly before and after methanol treatment. The sharp spectral peak of the neutral exciton in the methanol-treated sample was shifted to the higher energy side by 18 meV compared to the peak in untreated sample. This shift made the emission peak due to charged excitons clearly visible. Detailed fitting analysis revealed that the methanol treatment relaxed the tensile strain in the nano-sized WS₂ monolayer grown on SiO₂/Si substrate. In addition to the measurements in air, the results in vacuum and their temperature dependence also support this interpretation. Since this methanol treatment is simple, does not cause sample loss, and does not reduce luminescence efficiency, it may be an effective means to relax strain from nanoscale transition metal dichalcogenides monolayers.

The hydration structure and electronic state of Li⁺ doped complexes on the surface of C₆₀ were investigated by density functional theory calculations. This system is a simple model for the solvation of Li⁺ at the anode of a lithium-ion battery. C₆₀ and Li⁺ bind at approximately 35 kcal mol⁻¹. The new band of C₆₀ formed the lowest excited state, 0.1 eV smaller after interaction with Li⁺. The water molecule preferentially interacted with the Li portion of the C₆₀-Li⁺ complex, and a micro-hydration structure was formed around Li⁺. When four or more water molecules were added to the system, Li⁺ was removed from the C₆₀ surface by the water molecules, and a hydration shell was formed around both Li⁺ and C₆₀ (separate hydration). The electronic interaction between C₆₀ and Li⁺ was completely disrupted by the formation of a microscopic-hydrated shell. Herein, the mechanism is discussed based on the theoretical results.

Copper thin film has been identified as a promising material for multi-level interconnecting materials in IC fabrication due to its unique electrical properties and high electrical conductivity. However, it is very challenging to manufacture a superior planar surface with low dishing and minimal erosion of copper thin film in the chemical mechanical polishing (CMP) process. In this study, the micro-topography model of a soft polishing pad is performed using an X-ray micro-computed tomography scan combined with finite element method simulation to evaluate the contact area between the CMP pad and wafer during the CMP process. Additionally, the material removal rate (MRR) model for the copper wafer is calibrated based on the wear of the material between abrasive particles and the wafer surface. The results of this study not only investigate the effect of CMP pad asperities during the CMP process but also provide a new method for fully calibrating MRR in comparison with CMP experiments for the verification of model parameters.

With the construction of the energy internet, the demand for various sensing devices is increasing. Most of sensing devices need power source which limits their application in the wide spread distributed nodes of sensor network. Therefore, there is an urgent need to develop passive sensing devices which is more intelligent and convenient. This paper studies the magnetoelectric effect of layered magnetoelectric composites. Firstly, the physical process is analyzed by using the finite element method. Secondly, magnetoelectric response of the eddy current in the Cu-PZT layered composite material is investigated. Finally, the voltage variations of circular and rectangular samples are compared. It can be seen from the results that under the action of the eddy current, there is a u-shaped curve relationship between the induced voltage and the magnetic field. The energy conversion of metal-piezoelectric composite material without power source provides an effective path for developing passive magnetic sensor.

(Ce_0.002 Y_0.998−x Lu_x)AlO₃ (x = 0.000, 0.010, 0.100, 0.200) single crystals were grown and characterized to clarify the effects of Lu substitution in Ce:YAlO₃ on its crystal structure, optical properties and thermal stability of Ce³⁺ luminescence. The lattice constants of (Ce_0.002 Y_0.798 Lu_0.200)AlO₃ were comparable to those of Ce:YAlO₃, so the crystal structure was not significantly influenced by Lu substitution. Concerning the optical characterization, the absorption and emission spectra were almost the same regardless the amount of Lu substitution. This result is consistent with the assumption that the crystal field is not influenced by Lu substitution. The temperature dependences of the photoluminescence decay time showed that the quenching temperature (T_50%) tends to increase with the increasing Lu concentration. We conclude that the leading quenching mechanism is the thermally activated ionization which is suppressed by the Lu substitution in Ce:YAlO₃.

When light propagates through a scattering medium, imaging of an object hidden behind the scattering medium is difficult due to wavefront distortion. Scattering imaging is a technique for reconstructing images by solving the problem of complex reconstruction from speckle images. Tracking moving targets behind a scattering medium is a challenge. Scattering imaging using deep learning is a robust technique that learns a huge number of pairs of ground-truth images and speckle images. Here, we demonstrate tracking of moving targets with an extended depth of field behind a scattering medium based on deep learning of speckle images acquired at different depths. We found that it was possible to track moving targets over a wide axial direction by increasing the number of trained positions.

A terahertz spoof surface plasmonic polaritons waveguide with metallic rectangular spiral is proposed in the paper. By analyzing dispersion relation and electric field distribution, it is found that the proposed waveguide has a lower asymptotic frequency, a tighter localized field with 11.7 times enhancement, and a more compact size compared with the T-grooves waveguide. Based on a rectangular spiral waveguide structure, a compact and very sharp roll-off lowpass filter is investigated and experimentally verified by scaling down frequency to the microwave region. The fabricated lowpass filter has a high roll-off rate of 566 dB GHz⁻¹, ultrahigh figure-of-merit of 43039, and compact size. Therefore, it may be applicable for various compact integrated devices and circuits in THz and microwave frequency ranges.

This work proposes a page differential intensity amplification for optical signal amplification in the intensity multiplexing holographic data storage system. The proposed method detects the signals of four cameras and reconstructs the intensity difference between two pages. The reconstructed intensity difference is amplified by the ratio of the readout beam amplitude to the local oscillator beam amplitude. Experiments showed that the proposed method can achieve a more stable signal amplification than the conventional amplification technique. Moreover, signal detection is possible with one third the intensity of the readout beam compared to the conventional direct detection method. This corresponds to 1.8 times the recording capacity increase if the capacity is limited by M/#, or the reduction to one third the readout exposure time.

Watt-class wavelength conversion is expected by enlarging the mode size of the channel waveguides to dozens of micrometers to avoid optical damage with high-power pump lasers. In this work, uniform periodically-poled (PP) structures in MgO doped stoichiometric LiTaO₃ were fabricated by applying voltage with a SiO₂ insulation layer. Annealed proton-exchanged waveguides with a full width at 1/e² maximum in a width of 43 μm with an in-depth of 28 μm were obtained by proton exchanging for 4 h and thermal diffusion for 75 h. This waveguide can be excited by pump waves with a power of 8.6 W considering the optical damage threshold. Second harmonic generation with a wavelength of 515 nm was conducted in the low power region of about 35 mW to investigate the basic characteristics. Normalized wavelength conversion efficiency in the 15 mm long PP structures was estimated to be 4.3% W⁻¹.

We investigated the effect of stoichiometry on the spin Hall angle of the half-Heusler alloy topological semimetal YPtBi by changing the composition ratio r of Y/Pt from 0.5 to 1.9. We confirmed that YPtBi with high C1 ordering can be deposited by co-sputtering at r = 0.5–1.5, and a large effective spin Hall angle ${\theta }_{{\rm{SH}}}^{{\rm{eff}}}$ of 1.7 was achieved in a junction with Pt/Co/Pt at the exact stoichiometry r = 1.0. The ${\theta }_{{\rm{SH}}}^{{\rm{eff}}}$–conductivity relationship is similar to that observed in samples with exact stoichiometry, indicating that the spin Hall effect in YPtBi is robust against the change of its stoichiometry.

In this paper, the differential equations of the conductive filament growth are suggested on the basis of the jump conduction of ions in the dielectric film. We solved these equations by means of the average value method, obtaining the calculative formula of the forming and set time. Then, we proposed an algorithm of getting the jump rate, the jump distance, and the potential barrier. These parameters are linked with the forming and set time. As a result, the model of calculating microscopic parameters for the conductive filament growth is built. Besides calculating microscopic parameters, this model can also be used to compute the electrical parameters of ions and electrical characteristics of the conductive filament in the forming and set processes, such as the mobility of ions and the current in the process of the conductive filament growth. The calculated data of the model are consistent with the experimental results.

We elucidate a photocarrier collection mechanism in intermediate band solar cells (IBSCs) with InAs-quantum dots (QDs)-in-an-Al_0.3Ga_0.7As/GaAs-quantum well structures. When the Al_0.3Ga_0.7As barrier is excited, the device electrical output can be varied by additional infrared light for the electron intraband optical transition in QDs. The photocurrent in IBSC with a single QDs-in-a-well structure shows a monotonic increase with the intraband-excitation density. Conversely, IBSC with a multilayered QDs-in-a-well structure exhibits a photocurrent reduction when electrons in QDs are optically pumped out. The simultaneously measured photoluminescence spectra proved that the polarity of QD states changes depending on the intraband-excitation density. We discuss the drift and diffusion current components and point out that the hole diffusion current is significantly influenced by carriers inside the confinement structure. Under strong intraband excitations, we consider an increased hole diffusion current occurs by blocking hole-capture in the quantum structures. This causes unexpected photocurrent reduction in the multilayered device.

We investigated the impact of various excitonic and photonic losses on the lasing threshold and slope efficiency of organic semiconductor lasers (OSLs) under optical and electrical excitations. The rate equations are solved numerically using the Euler method for an OSL and an organic semiconductor laser diode, including 4,4'-bis[(N-carbazole)styryl]biphenyl (BSB-Cz) as a gain medium. The results showed that the loss mechanisms that affect the exciton and photon densities cause an increase in the laser threshold and a decrease in the slope efficiency. Further, we demonstrated that by using a thermally activated delayed fluorescence (TADF) emitter as a gain medium, the triplet excitons could be harvested by increasing the reverse intersystem crossing rate (k_RISC), resulting in an appreciable decrease of the laser threshold and an increase of the slope efficiency. Accordingly, the TADF emitters with a fast k_RISC are expected to significantly reduce the current density required for electrical excitation.

Thermoelectric properties of finite graphene nanoribbons (GNRs) coupled to metallic electrodes are theoretically studied in the framework of tight-binding model and Green's function approach. When the zigzag sides are coupled to the electrodes, the electron transport through the localized edge states can occur only if the channel length between electrodes is smaller than the decay length of these localized zigzag edge states. When the armchair edges are coupled to the electrodes, there is an interesting thermoelectric behavior associated with the mid-gap states when the GNR is in the semiconducting phase. Here we show that the thermoelectric behavior of zigzag edge states of GNRs with armchair sides connected to electrodes is similar to that of two parallel quantum dots with similar orbital degeneracy. Furthermore, it is demonstrated that the electrical conductance and power factor given by the zigzag edge states are quite robust against the defect scattering.

Gold clusters trapped on opaque substrate particles were produced using pulsed laser ablation. The ablation laser irradiated the target Au plate in a liquid dispersed with opaque substrate particles. It was found that the rate of thermal diffusion from the smaller particle that absorbed laser energy was greater than that from the larger particle; therefore, it is less likely to increase the temperature. Subsequently, the Au target was ablated more efficiently than the opaque substrate particles dispersed in the liquid. Therefore, the opaque particles were barely miniaturized and remained intact. The interaction mechanism of the deposition of the Au particle produced by laser ablation on the substrate particles was investigated by measuring the zeta potential of the substrate particles. The positively charged Au particles were adsorbed by ion exchange with positively charged Y₂O₃ substrate particles. In contrast, they interacted via electrostatic interactions with negatively charged α-quartz and ZSM-5 zeolite particles.

The surface properties of hemoglobin bound to O₂ (HbO₂) or CO (HbCO) were investigated by ethanol precipitation, particle size analysis, and ζ potential measurements. We found that, compared with HbO₂, HbCO is surrounded by more hydration water molecules, resulting in the greater physicochemical stability of HbCO in aqueous conditions. The intermolecular interactions of HbO₂ and HbCO were studied by acquiring atomic force microscopy images under ambient air conditions. HbCO molecules easily aggregated on the hydrophilic mica substrate compared with HbO₂ molecules during the dewetting process. We discuss these results in terms of a competing process between dispersion forces and adsorption on the hydrophilic mica substrate. The observed results suggest that the local structural differences between Fe–O₂ and Fe–CO influence the surface structure of the protein, leading to the observed dissimilar physicochemical properties of HbO₂ and HbCO.

Electrostatic properties of different C₆₀ thin films under external electric fields have been investigated from first-principle total-energy calculations. Density functional theory calculations combined with the effective screening medium method reveal that the electrostatic properties of C₆₀ thin films in an electric field strongly depend on the arrangement and conformation of the C₆₀ molecules. The relative permittivity across the thin films exhibits clear a positional dependence resulting from the π electron distribution within the films. An electrostatic polarization is uniformly induced by weak electric fields, typically 0.1 V nm⁻¹, because of the semiconducting electronic structure of the thin films, whereas the polarization is highly concentrated in the outermost C₆₀ layer under strong electric fields of 0.5 V nm⁻¹.

Tungsten oxide (WOx) is expected to act as a photocatalytic material under visible light. We have deposited WOx thin films using radiofrequency sputtering and evaluated the photocatalytic activities of the films via degradation of methylene blue solution. The optical absorbance, crystallization, and surface morphology of the WOx thin films were also investigated. The absorption edge of the WOx thin films was shifted to the long-wavelength region when the substrate temperature was high and the O₂ gas flow rate was low. Crystallization proceeded when the substrate temperature was high and additional WOx diffraction peaks were appearing with low O₂ gas flow during growth. Furthermore, the grain size of the WOx thin films was smaller when the O₂ gas flow was high. The photocatalytic activity was higher when the substrate temperature and O₂ gas flow rate were low.

An integration method of silicon nanowires (SiNWs) bridges in microtrenches was demonstrated combining a local arrangement of catalyst Au nanoparticles by two-step UV lithography, and a vapor–liquid–solid (VLS) bottom-up growth with perpendicularity promotion by surface nanoholes with metal-assisted chemical etching. Au nanoparticles with a diameter of 60 nm were arranged on one-side walls of 10 µm wide microtrenches, with two types of area sizes to evaluate the influence on the yield of SiNWs bridges reaching opposite sidewalls. A four-hour VLS process at 500 °C produced perpendicular SiNWs bridges in the microtrenches, and a higher yield was obtained with a narrow-area arrangement: a 30.7% ratio of densities of SiNWs bridges to Au nanoparticles, and a 2.1/µm² density in the arrangement area. Fewer SiNWs showed initial oblique growth there, and most of the bridges had a linear morphology. The yield of SiNWs bridges was discussed focusing on depth positions in microtrenches and the depths of surface nanoholes.

We report the successful Kyropoulos growth of a large strontium tetraborate (SrB₄O₇, SBO) single crystal that weighs more than 300 g. In order to grow the large and transparent crystal, a new twin-type stirring blade was used along with a 150 mm diameter crucible. The use of the stirring blade results in the production of the world's largest SBO crystal with dimensions of 100 mm (a) ×30 mm (b) ×32 mm (c), a weight of 328.2 g, and wide transparency down to 130 nm. These results will then lead to the development of large SBO crystals as optical window materials for high-power DUV laser processing systems.

The dependencies of concentrations of thermal equilibrium vacancies and interstitials on temperatures in Si crystals are determined directly, which has been a long-standing issue since the 1950s. They are evaluated by combining the formation energies and self-diffusion entropies deduced from the analyses of self-diffusion coefficients, and migration entropies deduced from diffusion coefficients of point defects. The concentrations as the number density of thermal equilibrium vacancies and interstitials at temperature T (K) are determined to be 5 × 10²²exp(6.5)exp(–3.85 eV/k_BT) and 5 × 10²²exp(10.6)exp(–4.3 eV/k_BT) cm⁻³, respectively. The diffusion coefficients of vacancies and interstitials are determined to be 2.7 × 10⁻³exp(–0.45 eV/k_BT) and 2.5 × 10⁻² exp(–0.49 eV/k_BT) cm² s⁻¹, respectively. The results are discussed in comparison with those reported experimentally.

We demonstrated high-electron-mobility transistors (HEMTs) with enhanced two-dimensional electron gas (2DEG) mobility using a low-strain AlGaN barrier grown by metalorganic vapor phase epitaxy under a nitrogen atmosphere. We investigated the effects of the growth temperature under a nitrogen atmosphere on the electrical properties of AlGaN-HEMT structures, focusing on 2DEG mobility. At growth temperatures below 855 °C, the 2DEG mobility decreased with decreasing growth temperature owing to an increase in the threading dislocation density. However, at growth temperatures above 855 °C, the 2DEG mobility decreased with increasing growth temperature. This finding was attributed to the compressive strain in the GaN channel, which increased with increasing growth temperature owing to the increased tensile strain in the AlGaN barriers. We concluded that temperatures around 855 °C are suitable for AlGaN barrier growth under nitrogen atmosphere. Finally, we achieved the highest 2DEG mobility of 2182 cm² V⁻¹ s⁻¹ with a low sheet resistance of 406 Ω sq⁻¹. using an Al_0.41Ga_0.59N barrier.

Herein we report on the positive Seebeck coefficient S = 162 μV K⁻¹ of niobium (Nb)-doped MoS₂ films prepared by sputtering and activation of Nb atoms by sulfur vapor annealing. The p-type doping achieved via these processes is discussed based on changes in chemical bonding states and resistivity behavior in terms of annealing and measurement temperatures. The results of this study provide a new option for p-type doping of MoS₂ films and are expected to contribute to the development of nanoelectronics and a smart society.

In this study, we describe the signal readout capabilities of indium–tin–zinc-oxide (ITZO) thin-film transistor (TFT)-based active pixel sensor (APS) pixel circuits combined with organic photoconductive films (OPFs). A pixel circuit was fabricated with a size of 50 μm containing three ITZO TFTs having a channel length of 2 μm and a blue-sensitive OPF possessing excellent properties with an external quantum efficiency of ∼59% and a dark current density of <100 pA cm⁻². Signal readout operation of the pixel circuits in accordance with irradiated light intensity was demonstrated, and sufficient response speeds within the line selection period, assuming a pixel number of 320 × 240 (QVGA) at 60 frames per second (∼69.4 μs), was also confirmed by fabricating pixel line arrays comprising 320 and 240 pixels. Our findings show that the miniaturized ITZO TFTs have potential for use in high-pixel-density TFT-based APS image sensors with improved imaging quality.

TiO₂ nanostructure could be produced at below 100 °C by means of liquid phase deposition (LPD), which is a green approach with low cost and low impact on the environment. The improvement of crystallinity is one of the main challenges toward efficient photocatalysis. Herein, we investigated the dependence of synthesis temperature on the crystal structure of TiO₂ photocatalysts to provide higher photocatalytic efficiency. Scanning electron microscopy, X-ray diffraction, and Raman spectroscopy analysis confirmed the formation of waxberry-like TiO₂ with an anatase phase with a synthetic temperature up to 80 °C. Both reaction temperature and time are found to dictate the crystallinity, structure, and size of the products, which could be attributed to the hydrolysis of a precursor (ammonium hexafluoro titanate), as well as the aggregation and coagulation of primary particles. The product synthesized at 70 °C for 3 h exhibited higher crystallinity, which led to higher photocatalytic efficiency observed based on the decomposition of methylene blue.

In the present work, the high-rate epitaxial growth for superconducting YBa₂Cu₃O_7-δ (YBCO) films on the substrates of LaMnO₃(LMO)/IBAD-MgO/Y₂O₃/Al₂O₃/Hastelloy is achieved by fluorine-free metal organic deposition (FF-MOD) by rapidly switching the partial oxygen pressure (pO₂) at a fixed temperature. Further investigation into the effects of temperature and switching pO₂ on the phase transition of YBCO elucidates that the growth mode and microstructural characteristics of the studied films. BaMnO₃ heterogeneous particles are observed in localized regions in the films by cross-sectional transmission electron microscopy, which may be generated by the interfacial reactions between the substrate and transient liquid phases. The present work implies the feasibility of FF-MOD for the rapid growth of YBCO films on LMO buffered metallic substrates, regardless of interfacial reactions during the preparation.

The numerical simulations of the initial plasma dynamics induced by 1064 nm laser irradiation on a KCl-Ti mixture target in a laser-triggered vacuum switch are performed. The simulation results showed that laser irradiance strongly affects the dynamics of the initial plasma. With higher laser fluence, the plasma plume will have higher temperatures and densities, and the shock front will also move faster. During the laser ablation, the plasma shielding is a non-negligible process. As the degree of ionization increases, the absorption coefficient of the plume increases and the it begins to absorb the laser energy. The temperature and velocity of the plume increase dramatically as it absorbs laser energy. When laser fluence gets higher, the plasma shielding starts with a shorter time and a larger proportion of the laser energy is absorbed by the plume.

The concentration distributions of chemically reactive species in water exposed to low-temperature atmospheric-pressure plasma (APP) have been studied with one-dimensional numerical simulations. Highly reactive species supplied from an APP to the water surface all react in the "reaction boundary layer," i.e. a thin layer with a thickness of about 100 nm on the solution side of the interface, and are converted to stable species. This study quantitatively shows that, in the case of pure water irradiated by an APP, the simultaneous presence of H₂O₂, NO₂⁻, and O₃ in the solution is the only cause to make it an oxidizing medium as they continuously produce ONOOH and HO₃, which then decay to generate OH radicals in the solution bulk. ONOOH and its accompanying HO₂NO₂ have much longer diffusion lengths than HO₃ and therefore their diffusion can also contribute to the oxidizing capability of the solution.

In order to improve the power capacity of a high-power microwave (HPM) generator, a Ku-band radial transit time oscillator (RTTO) with a trapezoidal resonator is designed. Compared with the traditional RTTO, both the modulation cavity and the extraction cavity are trapezoidal, which can modulate the electron beam more effectively. At the same time, the conductor tips on both sides of the cavity are farther, which helps to avoid the enhancement of the local electric field at the conductor tip, so as to reduce the risk of radio frequency (RF) breakdown. In particle-in-cell (PIC) simulation, the proposed Ku-band RTTO can output HPMs with the power of 1.66 GW and the frequency of 14.33 GHz, and the working efficiency is 41%. The maximum radial electric field intensity in the extraction cavity is 0.76 MV cm⁻¹, lower than the RF breakdown threshold of metallic materials, which can effectively improve the power capacity of the device.

The arbitrary electron energy distribution function (EEDF) of cold atmospheric-pressure plasma is determined from optical emission spectroscopy measurement. Using the electron-neutral bremsstrahlung-dominated continuum spectrum and relevant cross-section data, a partial arbitrary EEDF can be reconstructed through the reinforcement learning-based visible bremsstrahlung inversion method. From an atmospheric-pressure argon dielectric barrier discharge plasma emission spectrum (440–900 nm), a partial arbitrary EEDF can be determined with a resolution of 0.2 eV. The resemblance between the obtained arbitrary EEDF and a two-temperature Maxwellian was found with ${T}_{{\rm{e}}}$ = 0.26 and 2.2 eV. The EEDF range is mostly constrained by the spectrum wavelength range.

This paper uses a cross-track DC noise measurement technique to determine the written track width in heat-assisted magnetic recording (HAMR). The method is approached as a simple, no-extra-hardware-required technique on a spin-stand to determine the written track width as well as the DC noise amplitude at the center track in a HAMR system. The track width data show the expected trends with changing laser operating current (${I}_{op}$) and write current (${I}_{w}$), and they are strongly correlated with track density capabilities and physical near-field transducer (NFT) peg width. The written track width is essentially defined by the ${I}_{op},$ which increases as ${I}_{op}$ increases. The method is useful for comparing the magnetic responses of different writer pole or NFT peg geometries, as well as media design comparison to provide insight into the head/component necessary to improve HAMR system performance, which is useful HAMR recording parameters for head/media designers and test engineers.

We extract the electric properties of border traps with long time constant in low-pressure chemical vapor deposition (LPCVD) Si₃N₄/GaN/AlGaN/GaN metal–insulator–semiconductor (MIS) structure using quasi-static capacitance voltage method. The energy and depth distribution of the border traps is calculated based on the analysis of energy band diagram and charging dynamic of border traps in the MIS structures. With this method, it is found that LPCVD Si₃N₄/GaN/AlGaN/GaN MIS structure have a high density of border traps in the order up to 10²¹ cm⁻³ eV⁻¹ located at energy level between E_C,GaN − 0.04 eV and E_C,GaN − 0.66 eV with distance of 1.0–4.2 nm from the Si₃N₄/GaN interface. Microstructure analysis suggests that the high density of border traps is possibly correlated to the oxygen content at the Si₃N₄/GaN interface. Meanwhile, the proposed method is also suitable for MIS or metal-oxide-semiconductor structure on other semiconductors, providing another powerful tool to analysis the physical properties of border traps.

A simple dose calculation tool, SiDE, was developed for dose evaluation in a water phantom for boron neutron capture therapy, which makes the calculation time much shorter compared with the conventional particle transportation Monte Carlo codes and is applicable to any type of incident neutron spectra to the phantom. As the SiDE can not only calculate quantitatively the dose distribution in the phantom but also output dose indexes such as advantage depth and peak tumor dose, a comparison between different boron neutron capture therapy neutron sources can be easily performed. Consistency with a Monte Carlo transportation code was verified through comparison with the conventional dose calculation with the Particle and Heavy Ion Transport Code System, and the calculation time was nearly 1/90 in the SiDE. The dose distributions for a reactor and accelerator-based neutron sources were compared, and the differences were found to be small although large differences existed between the incident spectra.

We investigated the radiation damage process of commercially available light-emitting diode (LED) lightings in an X-ray radiation environment such as the electron storage ring SPring-8. It was found that metal-oxide-semiconductor field-effect transistors (MOSFETs) in the LED power supplies were damaged by X-ray irradiation by a total dose effect greater than several hundred Gy (air kerma). To visualize the whole damage process, we performed in situ measurement of the MOSFET under an irradiation from an X-ray tube. The result clearly showed a sudden increase of the off-state drain current accompanied by a sharp increase of MOSFET temperature as a function of radiation dose, which eventually caused the device failure. We supposed from the result a significant increase in device lifetime by switching off the LED power supply and experimentally verified it by observing the increase of lifetime by an order of magnitude or more under the same irradiation condition.

The improvement of power capacity would benefit greatly from the analysis of transient characteristics of bulk acoustic wave (BAW) devices. For this purpose, a measurement system was established, which could capture the temperatures and the insertion loss (IL) of the BAW devices simultaneously. Based on the obtained testing data of four different commercial BAW filters, we clarified the time dependence of device temperature and IL. The results showed that the BAW filters would exhibit higher power capacity with higher threshold frequency and a lower slope of the characteristic curves. This prompts us to propose an evaluation method for BAW filters under high power levels, which could improve the efficiency of device selection and performance prediction.

We designed/proposed kinds of new-parallel connections of the Helmholtz resonator with embedded apertures (HREAs). The design rule of the resonator, aperture, and length of the embedded hole has much influence on the sound absorption characteristics of the metamaterials. The multiple nearly perfect sound absorption peaks in a wide frequency band were obtained. The results show that by accurately balancing the coupling parameters of the new-parallel connection of the HREAs, the resonators can have continuous excellent sound absorption performance in multiple frequency bands. The frequency of the absorption peak can be controlled by adjusting the geometric parameters of the resonator, and the absorption bandwidth can also be flexibly adjusted with a fixed thickness. The working wavelength of the designed new-parallel connection of HREAs is approximately 57 times its total thickness (43 mm), and the average sound absorption coefficient can be as high as 0.8.

We experimentally evaluate the tolerance of a repeater laser (RL) method, which generates a reference wave using a phase-locked laser. The tolerance to the optical power variation of a plane wave component in a split object wave is limited by the dynamic range of an imager to record holograms in a conventional method, whereas it is limited by that of a photodetector for phase-locking in the RL method. The RL method using a commercial imager and photodetector achieved constant high measurement accuracy under the varying range of 50 dB and 100 times higher tolerance than the conventional method.

A strain-insensitive high-sensitivity temperature sensor based on multimode interference in a specialty fiber with a square core is developed and experimentally investigated. A 25 cm long square-core fiber is used as a multimode fiber (MMF) of a single-mode–multimode–single-mode structure and the temperature dependence of its transmitted spectrum is measured while the strain is applied continually from 0 to 500 με with steps of 100 με. The mean temperature sensitivity is −22.35 pm °C⁻¹, which is ∼3.5 times higher than that of a standard MMF, and it is almost independent of strain with a small standard deviation of 0.44 pm °C⁻¹.

Reported experimental results on homoepitaxially grown nitrogen-doped 4H-SiC on (03$\bar{3}$8) and misoriented (0001) substrates under carbon-rich conditions in a SiH₄–C₃H₈–N₂–H₂ system were analyzed according to surface diffusion theory dealing with step kinetics. On misoriented (0001) surfaces at 1723–1873 K, the relaxation time for a silicon adatom to enter a step was negligibly small. This finding, however, was not the case with the relaxation time for nitrogen-containing species (τ^k_N). The ratio of τ^k_N to the residence time of the nitrogen-containing species on the surfaces was estimated to be 0.1–0.2 at 1723–1823 K and 0.04 at 1873 K.

In this study, we analyzed the slow decay in time-resolved photoluminescence (TR-PL) of n-type GaN homoepitaxial layers with carbon concentrations of (0.26–4.0) × 10¹⁶ cm⁻³. The relative signal intensities of the slow decays to the TR-PL signals at t = 0 s increased almost linearly with increased carbon concentration, suggesting that the carrier recombination process is subjected to the deep level formed by the carbon atoms in GaN. Slow decay curves were calculated based on the rate equations for trapping and emission at the deep level. The experimental carbon concentration dependence of the time constants and the relative signal intensities was reproduced by calculation. TR-PL is a technique used to estimate carbon concentrations in GaN homoepitaxial layers.

Optical correlation-domain reflectometry (OCDR), which is known as one of the fiber-optic techniques for distributed reflectivity sensing, conventionally included an acousto-optic modulator, a reference path, and erbium-doped fiber amplifiers in its setup. In this work, by removing all of these components simultaneously, we develop a super-simplified configuration of OCDR, which consists of a light source and a photodetector only. We experimentally show that this system can still perform distributed reflectivity sensing with a moderate signal-to-noise ratio, which will boost the portability and cost efficiency of the OCDR technology.