Table of contents

A non-equilibrium electronegative plasma serves as the reactive source for semiconductor dry processing as an advanced technology. This paper reviews the current knowledge about the fundamental processes, structures, dynamics, and functions of high-frequency electronegative plasmas investigated over the past 30 years, and discusses the hidden characteristics originating from a majority of positive and negative ions and a minority of electrons. A unique structure with a negative ion layer is emphasized in terms of the sustaining mechanism underlying capacitively coupled plasma. In a strong electronegativity, the main sustaining mechanism is caused by a cluster of ionizations placed in front of the instantaneous anode by a minority of electrons accelerated from the bulk plasma into the active double layer. A new insight is obtained for how to hold a bulk plasma. The bulk plasma is maintained by a time-averaged net ionization rate equal to the electron attachment by minority electrons under the assistance of a relatively high reduced field E(t)/N_g in order to compensate for the large loss by ion–ion recombination. The structure is quite different from that of an electropositive plasma having a low reduced field under ambipolar diffusion. It is proposed that it will be possible to estimate the high value of E(t)/N_g in bulk plasma in a strongly electronegative plasma on the basis of the static DC breakdown theory in electronegative gas.

The femtosecond laser amplifier has attracted much attention as a promising tool for cell processing and manipulation. The focused pulse with high peak intensity induces not only 3D selective laser ablation, but effective generation of a shockwave and stresswaves. Under a microscope, these waves act on cells near the laser focal point as an impulsive force. This force has been applied as an external trigger to estimate intercellular adhesion strength, to manipulate single cells and to investigate the mechanobiology. In this review, we explain the kinetics of the impulsive force based on the femtosecond laser ablation mechanism, and introduce applications to the evaluation of intercellular adhesion, which is an essential issue in cell research for elucidating tissue formation and signal transduction between cells in the physiology and pathology. Based on these achievements, we predict future advanced applications to biology and engineering.

We review a quantitative evaluation method for the charge transport properties of organic semiconductors with static and dynamic disorder using wavepacket dynamics based on quantum theory. The large dynamic disorder in electronic states due to molecular vibrations induces transient localization of the charge carriers, which is a quantum interference effect and determines the intrinsic transport properties of the organic semiconductors. We show that our simulation can reproduce the experimentally observed mobility of single crystals including the temperature dependence. Furthermore, we estimate the effects of static disorder, such as impurities and defects, on the transport properties. To understand the transport properties of realistic organic devices, it is important to evaluate these properties based on quantum theory and consider the competition between static and dynamic disorder.

An X-ray standing wave (XSW) is created in the overlap region of two coherent X-ray waves, e.g. by diffraction or reflection. The XSW intensity maxima move, when traversing the range of total reflection, causing strong modulation of the photo-excitation of a particular element or atomic species, recorded by electron or X-ray fluorescence spectroscopy. The XSW technique is a Fourier technique, particularly useful for identifying and structurally characterizing diluted, active species. In simple cases, a single XSW measurement allows characterization with pm resolution. Otherwise, employing several XSW measurements, an image can be created by Fourier inversion allowing one to identify individual sites. The principle, strength and limitations of the XSW technique are reviewed briefly and we focus on three examples for identifying active sites: catalytically active Al in scolecite, magnetically active and counter-active sites of Mn in GaMnAs and sites on the SrTiO₃(001) surface active in the splitting of water.

The angular distributions of photoelectrons and Auger electrons from single crystal surfaces show characteristic diffraction patterns, which contain information on the local atomic structures surrounding the emitter atoms. Using computational reconstruction processes on the diffraction patterns enables us to determine the local atomic structures of, for example, dopants, catalytic active sites, and surface/interface structures. This method has become known as "photoelectron holography (PEH)". Several advanced photoelectron analyzers for PEH are now available at beamlines at SPring-8, the world's largest synchrotron radiation facility. Recently, the use of micron-sized photon beams, as well as pump-and-probe time-resolved techniques has become possible with relatively high energy resolution. Here, the experimental apparatus and some representative applications are introduced.

We investigate the dependence of the Curie temperature (T_C), electronic structure and magnetic properties on hole doping by Zn vacancy (V_Zn) generations in Zn(Sn, Mn)As₂ and (Zn, Mn)SnAs₂ using the Korringa–Kohn–Rostoker method incorporated with the coherent potential approximation and a local spin density approximation (KKR-CPA-LSDA) within density functional theory. We find that T_C of (Zn, V_Zn)(Sn, Mn)As₂ is strongly reduced by hole doping due to the reduced double-exchange interaction. In contrast to this, (Zn, V_Zn, Mn)SnAs₂ shows ferromagnetism because of the introduction of holes into paramagnetic (Zn, Mn)SnAs₂. In this case, T_C is significantly enhanced by the hole doping because of the increased double-exchange interaction.

Series of two-dimensional Auger electron intensity angular distributions (AIAD) were measured from a polycrystalline iron surface using a focused soft X-ray beam and a display-type analyzer. The Fe(110) surface was polycrystallized by annealing up to the Martensitic transition temperature in an ultrahigh vacuum condition. After cooling the sample to room temperature, the crystal orientations of the 21 × 21 scanned points were determined by Fe LMM AIAD measurements. Domain formation of sub mm size was confirmed. The domains oriented in the [001] direction were found adjacent to the domain oriented in the [110] direction, suggesting that the Martensitic transition progressed according to the Bain relationship. The chemical and magnetic properties of domains with different surface orientations were characterized by combining diffraction measurements with X-ray absorption spectroscopy techniques. We show here how the surface oxidation reaction as well as the magnetization axis depend on the surface orientation.

A new superconducting sample, Ba_1−xCs_xTi₂Sb₂O, was prepared and characterized in a wide pressure range. The maximum value of superconducting transition temperature, T_c, of Ba_1−xCs_xTi₂Sb₂O was 4.4 K for x = 0.25 at ambient pressure. The crystal structure was determined to be tetragonal [space group of P4/mmm (No. 123)]. The charge density wave/spin density wave transition was observed at 44 K for Ba_1−xCs_xTi₂Sb₂O (nominal x = 0.25) at ambient pressure, but the transition was suppressed by applying pressure. The pressure dependent X-ray diffraction showed no structural phase transition up to 23.4 GPa, but very interesting T_c–pressure (p) behavior was observed, i.e. the T_c decreases with an increase in pressure up to 4.0 GPa, but it increased above 4.0 GPa, suggestive of non-BCS type behavior. Thus, the systematic study on new pnictide superconductor, Ba_1−xCs_xTi₂Sb₂O, was achieved, and the fascinating behavior of superconductivity against pressure was discovered.

We numerically studied the effect of size and shape of graphene sheets on nanoscale peeling characteristics by atomic force microscopy (AFM). It was clarified that the simulated peeling processes of the graphene sheet connected to the cantilever spring of AFM were classified into typical four types of the peeling force curves. This classification of the peeling process could be clearly understood in the phase diagram plotted as a function of the length and width of the peeled graphene sheet.

We investigated the effects of low-energy (<15 eV) ion bombardment on the properties of Al₂O₃ plasma-enhanced atomic layer deposition (ALD) films. High-flux ion bombardment caused interfacial mixing with underlying material of Si, and AlSiO_x films were formed instead of Al₂O₃ films. The interfacially mixed AlSiO_x films were selectively formed on single-crystal and amorphous Si surfaces, whereas normal ALD Al₂O₃ films were formed on SiO₂ surfaces. The interfacially mixed AlSiO_x films possessed thin (∼0.8 nm) SiO_x interlayers and abrupt interfaces. The interfacial mixing synthesis has the potential to realize simultaneous area and topographically selective depositions in combination with selective etching.

The effects of an applied electric field on hen egg-white lysozyme (HEWL) crystallization at low temperature were evaluated using a transparent cell exposed to a uniform internal electric field. The application of a low voltage at low frequency changed a phase diagram at low temperature to widen the solution regions suitable for protein crystallization. An alternating low electric field at low frequency can support the production of good-quality HEWL crystals in solution at low temperature around the undersaturated/supersaturated regions and may control protein crystal growth.

The positron annihilation lifetime spectroscopy (PALS) of cavansite crystals collected from Wagholi, Pune district of Western Maharastra, India were characterized by ⁶⁰Co gamma radiation with an irradiation dose of 1 Mrad and 3 Mrad at ambient conditions. The influence of γ-irradiation on the pore size and its content on cavansite structure were examined. The studies suggest ortho-positronium (o-Ps) lifetime (τ₃) and intensity (I₃) decreased upon γ-irradiation. The decreased o-Ps lifetime (τ₃) is attributed to the collapse of the framework structure of cavansite crystal. In addition, the reduction in o-Ps intensity (I₃) is known to decrease o-Ps annihilation sites because of free radical reactions.

We investigate the impacts of channel curvature induced by atomistic surface roughness on electronic-transport properties in monolayer transition-metal dichalcogenide field-effect transistors (FETs) through ab initio calculations. By focusing on the channel current, we demonstrate that the I_on current and I_on/I_off ratio are both significantly suppressed in n-type and p-type MoS₂ FETs when increasing the channel curvatures. We also evaluate the performance of CMOS inverters and demonstrate that the channel curvatures can dramatically reduce the inverter performance. These findings point to the fact underlining that surface engineering for channel roughness optimization at the atomic level is strongly required in MoS₂-based devices.

Channel hot carrier (CHC) reliability in In_0.7Ga_0.3As nMOSFETs with Al₂O₃/HfO₂ (EOT = 0.8 nm) during CHC stress has been studied in scaled-down gate devices. The threshold voltage degradation (ΔV_T) during CHC stress was attributed to the hot carrier injection into Al₂O₃ or/and HfO₂ defect sites, rather than charge trapping into high-κ bulk defects. Additionally, with an increase of gate voltage at a fixed drain voltage (V_DS), there was an increase in probability that the InGaAs channel carriers are easily injected into Al₂O₃ or/and HfO₂ defect sites, causing the worst ΔV_T degradation at the same V_GS = V_DS stress condition. Hence, hot carrier injection during CHC stress was divided into two components: charge injection by the vertical field near the source region and injection of hot carriers into the oxide bulk defects at the drain corner. To decouple the charge trapping and hot carrier injection into the gate oxide defect sites during CHC stress, an unrecovered (hot carrier damage) and recovery ratio (charge injection) of the ΔV_T degradation after relaxation and opposite polarity voltage were calculated to be about ∼70% and ∼30%, respectively. Therefore, hot carrier injection has emerged as a dominant degradation factor in InGaAs MOSFETs with high-κ dielectrics.

We investigated the temperature dependence of the spin-to-charge current conversion at nonmagnetic metal (NM: Cu or Ag)/Bi₂O₃ interfaces with Rashba spin-splitting. Spin pumping induced inverse Edelstein effects are measured in the temperature range from 290 K to 10 K. Estimated conversion coefficients at the Cu(Ag)/Bi₂O₃ interfaces are increased by 40 (17)% at 10 K compared with those at 290 K. The conversion coefficient is found to be proportional to the conductivity of the NM layer, indicating that the momentum relaxation process in the metal layer dominates the spin-to-charge current conversion process at NM/Bi₂O₃ interfaces.

The reduction of Si concentration in β-Ga₂O₃ crystals by the zone refining method was investigated. By the chemical analysis of a quenched β-Ga₂O₃ crystal coexisting with its melt at high temperature, the segregation coefficient for Si was estimated to be 0.54, revealing that Si as impurity is excluded from the solid to the liquid phases of β-Ga₂O₃ and zone refining is effective for purification. By repeating the zone refining process three times, the Si concentration showed a tendency to decrease gradually, as a numerical calculation simulates, and reached a level of ∼10¹⁷ cm⁻³.

By directly exciting the Tb³⁺ ion's ⁷F₆-⁵D₄ absorption line, the ⁵D₄-⁷F₅ emission underwent a serious thermal quenching from 333 to 813 K in CaWO₄ host. Through steady-state rate equation, it was shown in addition to the ⁵D₄ state's lifetime, the ⁷F₆ state's population also affected this thermal quenching. When using a diode laser at 405 nm to excite the Tb³⁺ ion's second lowest ⁷F₅ state, the ⁵D₄-⁷F₅ emission increased dramatically from 333 to 813 K. It reveals the thermal population from the lowest ⁷F₆ ground state to the higher ⁷F₅ state is one of the possible thermal quenching channels for the ⁵D₄-⁷F₅ emission.

This paper presents experimental results concerning the effects of properties of glass and ceramic dielectric on electrical characteristics of the dielectric barrier discharge (DBD). The effect has been examined with a focus on low frequency uni-polar pulse driving in order to eliminate influences induced by the presence of residual charges and mestastable states in the discharge volume. The results revealed that at low frequency, in the glass reactor, the discharge just occurred after a delay with respect to moment when a high voltage pulse is applied to the reactor, whereas this phenomenon was not observed in the case of discharge in the ceramic reactor. Furthermore, in the glass reactor, DBD was generated with a much higher current peak and shorter discharge current duration in comparison with the electrical characteristics of DBD generated in a ceramic reactor. The differences are presumed to be the result of the difference in ability of trapping and binding surface electrons of dielectric layers.

We study the electronic and optical properties of the mixed valence perovskite Cs₂Au₂X₆ (X = Cl, Br, I) using the fully relativistic all-electron calculations. We find that Cs₂Au₂X₆ exhibits indirect fundamental band gaps although the differences between the indirect and direct band gaps are small. For the electric field of light perpendicular to the tetragonal c axis, Cs₂Au₂Br₆ and Cs₂Au₂I₆ exhibit the maximum absorption coefficient of about 20 × 10⁴ cm⁻¹ around the photon energy of 2 eV, which is considerably larger than that of CH₃NH₃PbI₃. For the electric field of light parallel to the tetragonal c axis, the absorption coefficient of Cs₂Au₂I₆ is comparable to that of CH₃NH₃PbI₃ in the main part of the solar spectrum. Furthermore, we estimate the photovoltaic performance of Cs₂Au₂X₆ employing the spectroscopically limited maximum efficiency as a metric and discuss its dependence on the film thicknes in detail.

We report observation of the piezoresistive effect of β-Ga₂O₃ and investigate its application for strain gauge sensors. Ti/Au ohmic contacts are fabricated on commercially procured β-Ga₂O₃ materials. We employ the transfer length measurement pattern to remove the influence of contact resistance on the resistance measurement of β-Ga₂O₃ samples, especially when measuring the relatively small piezoresistance change due to strain. A gauge factor of −5.8 ± 0.1 is measured from a Ti/Au-β-Ga₂O₃-Ti/Au structure under tensile uniaxial stress in the [010] direction at room temperature.

The pressure and SiO-incorporation effect on the temperature dependence of dynamical properties for silicon oxide (SiO₂)_1−x(SiO)_x is theoretically studied by first-principles molecular dynamics. It is found that the incorporation of SiO enhances the selfdiffusions even under high pressure. The SiO effect on Si selfdiffusion is however reduced by the pressure at temperature lower than 4000 K, and the amount of reduction is larger for lower temperature, while the effect on O selfdiffusion is hardly reduced, being independent of the temperature. Such a difference is thought to come from the difference in selfdiffusion mechanisms between Si and O. It is indicated that the incorporated SiO acts as combined SiO interstitials rather than separate Si interstitials or O vacancies. This also suggests that the oxide viscous flow mechanism is a promising candidate for the origin of the Si missing in oxidizing Si nanopillars.

We investigated the carrier non-radiative relaxation process of InGaAs/GaAsP superlattice (SL) solar cells with different barrier thicknesses by combining piezoelectric photothermal (PPT) and surface photovoltage (SPV) measurements. The former technique detected heat generated by non-radiative relaxation and the latter detected the surface potential change induced by the carrier accumulation. Although the mechanisms of these measurements were different, corresponding signals of the transition between the quantum levels were observed in both spectra. The SPV signal intensities were independent of the barrier thicknesses. The carrier tunneling process functioned poorly under open-circuit conditions. Conversely, the PPT signal intensities increased with decreasing barrier thickness. We experimentally demonstrated that the non-radiative relaxation component increased as the barrier thicknesses decreased owing to the lattice relaxation at interfaces between the quantum well and barrier layers. We concluded that the non-radiative relaxation process in the SL structure must be directly evaluated to improve the solar cell performance.

The effect of long-range Coulomb interactions on electron transport in a one-dimensional ring is investigated by a numerical method with the time-dependent Hartree–Fock equation. Our results show that long-range Coulomb interactions induce a multi-electron wave packet state. Moreover, the number of electrons in the multi-electron wave packet varies depending on the strength of the long-range Coulomb interactions.

In the last decade, different solutions were proposed to boost the transmission bitrate of semiconductor lasers. Here, we focus on applying optical feedback to a semiconductor laser from an external cavity in order to induce enhancement of the modulation bandwidth up to 50 GHz as well as resonant modulation (RM) around frequencies approaching 60 GHz. High-speed modulation up to 90 Gbps under none-return to zero operation and a 45 Gbaud using pulse amplitude modulation-4 signals are predicted. Both types of improving the modulation performance of the laser are attributed to the photon–photon resonance (PPR) effect. The regimes of the external power reflectivity that correspond to both types of modulation response are specified. Comprehensive simulations are introduced to correlate the PPR frequency to the RM frequencies of the non-modulated coupled-cavity laser. Dependencies of the enhanced BW and PPR frequency on the cavity length and bias current are elucidated.

Nowadays, memristors are one of the most important ways to realize the nerve synapse. Memristors agree quite well with biological synapses, because they has an electrical resistance that changes from external application conditions. In this paper, we present a theory of the memristive principle of photoelectric-motivated memristors. And the photoelectric-motivated memristor is simulated to have the function of a biological synapse, including synaptic weights, spike-timing-dependent plasticity function, long-term and short-term plasticity, paired-pulse facilitation, and peak-dependent synaptic plasticity. Based on the actual test circuit, the weight of the synapse is adjustable. The photoelectric-motivated memristor provides a direction for the large-scale integration and application of light-controlled electronic synapses in CMOS technology.

When applying phase shifting interferometry to practical phase measurement, the wave may become non-sinusoidal, and could include some phase shift errors. Prior phase shift algorithms are primarily used for sinusoidal cases, and can cause system errors when used for these non-sinusoidal interference. We propose two phase recovery methods for non-sinusoidal interference fringes: specifically, a least-squares-based fitting algorithm that eliminates system errors using a sufficient number of measured images, and a Fourier transform-based method that effectively suppresses system errors using a lower (or insufficient) number of images. Simulation and experimental results verify the efficacy of the proposed methods.

A Monte Carlo ray-tracing simulation was developed for a transversely excited solar-pumped fiber laser without focusing optics. To make this possible, the fiber is immersed in a liquid sensitizer and sandwiched between highly reflective mirrors. The top reflector is dichroic to transmit solar radiation but reflect fluorescence to confine photons that match the absorption band of the active fiber. Simulation was used to evaluate the validity of the concept and optimize device performance. For comparison with the calculations, preliminary experiments were conducted by illuminating a 30 cm aperture, laser module with a solar simulator. The observed gains were in good agreement with the calculations for various conditions, such as sensitizer concentration and mirror reflectivity. Finally, we show that the predicted output power reaches 29 mW when the fiber length is optimized, and it will be enhanced to 150 mW with 0.21% solar-to-laser efficiency under the assumption of a reabsorption-free sensitizer.

The optical properties of Al_0.44Ga_0.56N/Al_0.59Ga_0.41N multiple quantum well structures with an In_xAl_1-xN insertion layer between the barrier layer and the well layer are investigated by using the effective mass theory. The numerical results show the TE-dominated emission can be realized by using the In_xAl_1-xN insertion layer, which can be mainly attributed to the larger separation of the electron-hole wave-function for the TM-dominated transition. Note that the rearrangement of valence subbands is also an important factor to enhance the TE polarization emission for the In_xAl_1-xN insertion layer with the lower In-content. The ratios of TE-polarized total spontaneous emission rate between the In_xAl_1-xN insertion layer structures (x = 0.11, 0.13, 0.15) and the conventional structure can reach 1.76–2.05 in the current density range of 2–300 A cm⁻² due to the larger product of Fermi–Dirac distribution functions of electron and hole. Furthermore, the In_xAl_1-xN insertion layer structures with x = 0.15–0.17 show the largest TE polarization emission.

Chemical vapor deposition has been developed to enable defect-free 4H-SiC crystals to be grown at lower cost and with higher growth rates. However, the structure and stability of 4H-SiC surfaces during crystal growth has not been clarified. In this study, we performed first-principles calculations and obtained the surface energies of ideal surfaces and Si-terminated surfaces on (0001), (000$\overline{1}$) and (1$\overline{1}$00) surfaces. For the (0001) and (000$\overline{1}$) surfaces, the Si-terminated surfaces are more stable than the ideal surfaces and Si atoms are adsorbed onto the surfaces up to high temperatures. The ideal surface on the (1$\overline{1}$00) surface is stable, and the Si-terminated surface changes to an ideal surface at lower temperatures than on the (0001) and (000$\overline{1}$) surfaces. These results indicate the possible temperature ranges in which to perform crystal growth. Thus, we clarified the conditions required to grow 4H-SiC crystals and the dependency of these structures on surface orientation.

We investigated the effect of an atmospheric pressure plasma treatment on a thermoresponsive ionic liquid device, which exhibits lower critical solution temperature type phase separation. The opaque state for the ionic liquid device with a polyimide treated by the atmospheric pressure plasma was dramatically stabilized, because H₂O microdroplets were pinned onto the polyimide. This surface-assisted stabilization originated from a hydrophilic interaction, such as hydrogen bonds between H₂O droplets and various oxygen-containing functional groups at the polyimide surface, which was generated by the atmospheric pressure plasma. This unique technique is expected to develop information display devices whose function is driven by temperature.

The mechanism of bubble removal in a narrow viscous fluid by using ultrasonic vibration is analyzed in this study. Experimental studies were performed on the adhesive bonding between a carbon fiber reinforced plastic (CFRP) laminate and an aluminum plate. After applying ultrasonic vibration on the CFRP laminate, it was found that the high-frequency vibration could induce an oscillating flow of the adhesive in the narrow bonding layer. Such a flow caused the entrapped bubbles to move and break until all of them were eliminated from the viscous adhesive. A fluid–solid coupling simulation and fluid tracer analysis were performed to analyze the underlying principle of bubble motion. The results reveal that because of the internal pressure of the bubble and the asymmetric characteristic of the fluid resistance around the bubble, the oscillating fluid induced by ultrasonic vibration drove the bubble to move in the direction closest to the edge. The reduction of the gas volume fraction in the adhesive resulted in an improved bonding between the CFRP laminate and aluminum plate.

Electron motion in a cylindrical chamber under RF electric field and confronting divergent magnetic fields was simulated to evaluate the phase-resolved profiles of power deposition to electrons in a low-pressure inductively coupled magnetized plasma. There were three primary regions where the power deposition was high; a region near the RF antenna, a region near the sidewall, and a region of the partial resonance. The phase-resolved profiles of the electron energy gain G(t) and azimuthal electron velocity v_θ(t) were obtained in every section defined in the chamber, and were fitted by functions with sinusoidal terms. The characteristics of G(t) and v_θ(t), e.g. their asymmetry and directionality, particular to the position were discussed by comparisons between different regions with the fitting parameters and their factors, such as the amplitude of electric field, that of the azimuthal velocity, the power factor, and the phase differences from the RF electric field.

The nonlinear longitudinal dust lattice wave of a one-dimensional dust chain under the influence of the plasma absorption effect was investigated. A modified KdV-Burgers' equation with the plasma absorption effect is derived under the continuum limit by the reductive perturbation method. Based on solutions of the Burgers' equation, the effects of dynamic damping, absorption coefficient, characteristic length and shielding parameter on the shock structure are investigated. It is found that shock wave polarity is determined by hydrodynamical damping. Furthermore, as the electron-to-ion temperature ratio increases, shock amplitude increases correspondingly, but its width remains basically unchanged. Therefore, the shock structure of nonlinear longitudinal dust lattice wave with plasma absorption potential is different from the one under the conventional Debye–Hückel potential.

The influence of Ni and Nb thickness on the electrical properties and high-temperature reliability of Ni(x)/Nb(100 – x)/n-type 4H-SiC ohmic contacts, where x = 25, 50 or 75 nm, was investigated. Two-dimensional X-ray diffraction, hard X-ray photoelectron spectroscopy and transmission electron microscopy analyses indicated that a relatively high Ni concentration had a strong influence on low specific contact resistance due to the greater formation of Ni₂Si at the contact interface, whereas a higher density of Nb improved the ability to collect excess carbon atoms by the formation of Nb₆C₅ at the interface, ensuring high-temperature reliability of the contacts. The experimental results showed that the Ni(50)/Nb(50)/4H-SiC ohmic contact is a potential candidate for high-temperature and harsh environment applications.

In this work, a graphene loudspeaker is designed using laser scribing technology, and its theoretical model with AC and (AC + DC) excitation is established, which focuses on the effect of different excitations on the performance of graphene loudspeakers. The proposed theoretical model consists of a temperature gradient model and a sound pressure model. The application of (AC + DC) excitation helps to mitigate the frequency doubling effect caused by AC excitation. Sound pressure level (SPL) measurements with AC and (AC + DC) excitations are carried out to verify the theoretical model. The measured results show that the SPL is proportional to the input power and inversely proportional to the measurement distance. The highest SPL produced by the graphene loudspeaker is 53.3 dB with (5 V_AC + 5 V_DC) excitation. The theoretical model of the graphene loudspeaker with different excitations has a certain reference value for further research on thermoacoustic effects and improving the efficiency of graphene loudspeakers.

The elevation of resist temperature during exposure to electron beam (EB) deforms the patterns of chemically amplified resists. The resist heating effect is a significant problem in mask production using a high-current EB mask writer. However, its mechanism is still unknown. In this study, the effects of electron thermal energy on the sensitization process of chemically amplified EB resists were investigated using simulation on the basis of their sensitization mechanism. The decomposition yield of sensitizers increased with resist temperature. The effect of the increase of decomposition yield on the critical dimension (CD) was calculated on the basis of the reaction mechanism. When the exposure pattern width was set to the same as the half-pitch (16 nm), the values of dCD/dT were 0.019, 0.013 and 0.010 nm K⁻¹ for the sensitizer concentrations of 0.2, 0.3 and 0.4 (molecules) nm⁻³, respectively. dCD/dT was decreased by decreasing the exposure pattern width.

Time-resolved observations of acoustic cavitation emission signals are important in understanding bubble cavitation dynamics and monitoring sonoporation efficiencies of ultrasound-assisted drug delivery systems. Previous methods using back propagation of such signals measure frequencies with high time resolutions but require post-processing. We propose a method using color Doppler ultrasound to obtain instantaneous frequencies of these signals from the phase differences with an external reference signal. Standard color Doppler processing is applied to both emissions and reference signals to enable real-time observations of bubble cavitation generated by high-intensity ultrasound wave irradiation. A sinusoidal wave signal was used to confirm the accuracy of our method with an estimation error of 8.59%. Experiments were performed using Sonazoid suspensions of two different concentrations. With a sound pressure of 1.0 MPa for the ultrasound wave, the type of bubble cavitation that is dominant is different before and after irradiation of about ten pulses.

A photoemission electron microscope (PEEM) system has been newly installed at the soft X-ray undulator beamline (BL17SU) of SPring-8 to realize time-resolved nanospectroscopy for the local transient electronic structures of advanced materials. This PEEM is a versatile machine composed of an electrostatic lens system and is intended for use in specific experiments such as time-resolved measurements. Pump–probe measurements in tandem with a femtosecond pulsed-laser system and an X-ray chopper are now readily available.

Fine-grained metals with sizes as small as 10 nm are deposited on nitrogen-incorporated carbon nanowalls to enhance field emission. The amount of metal coating is varied using the nominal thickness to control morphology and coverage of metal nanoparticles. The emission turn-on field decreases down to around 1.6 V um^–1 and 1.8 V um^–1 with increasing thickness of Ag and Au to 2 nm and 4 nm, respectively, and increases for further increase in thickness. A lower turn-on field corresponds well to a larger field enhancement factor, confirming that additional field enhancement with the morphological evolution of metal nanoparticles governs emission performance.

We fabricated a solid-state capacitor on an organic flexible substrate, which has an ultra-thin ferromagnetic Co electrode with a HfO₂ dielectric layer formed by atomic layer deposition. Tensile stress was applied parallel to the capacitor plane. The breakdown strain monotonically increases with a reduction in HfO₂ layer thickness. From the sheet resistance measurement, strain endurance up to 1.5% is realized in the capacitor with 10 nm thick HfO₂. A magnetic anisotropy of the Co layer is controllable by applying voltage between the Co and counter electrode. The modulation efficiency of the voltage-controlled magnetic anisotropy is almost independent of the strain.