Table of contents

GaAs metal–oxide–semiconductor (MOS) capacitors with HfTiON as a gate dielectric and Ga₂O₃(Gd₂O₃) (GGO) as an interlayer annealed in NH₃ or N₂ are fabricated, and their electrical properties are characterized. Experimental results show that the HfTiON/GGO/GaAs MOS device annealed in NH₃ exhibits a low interface-state density (1.1 × 10¹² cm⁻² eV⁻¹), a small gate leakage current (1.66 × 10⁻⁴ A cm⁻² at V_g = V_fb + 1 V), a large equivalent dielectric constant (25.7), and a good capacitance–voltage behavior. All these should be attributed to the fact that the GGO interlayer and postdeposition annealing in NH₃ can effectively suppress the formation of interfacial Ga/As oxides and remove the excess As atoms at the GaAs surface, thus reducing the relevant defects at/near the GGO/GaAs interface.

The electron mobility in HfO₂/In_0.53Ga_0.47As n-type metal–insulator–semiconductor field-effect transistors (nMISFETs) has been found to be significantly enhanced in the sub-1.0 nm equivalent oxide thickness (EOT) regime by annealing before the atomic layer deposition (ALD) of the HfO₂ gate dielectric. XPS measurements revealed that the predeposition annealing increased the amount of GaO_x and reduced the amount of AsO_x at the MIS interface, which is considered to reduce the trapped charge density and enhance the mobility, especially in the low-surface-carrier-density region.

The formation of a high-quality Ge_1−xSn_x layer has been examined on the basis of the understanding of the relationship between the stacking fault and the misfit strain between the Ge_1−xSn_x layer and the Ge substrate. We found that the crystallinity of the Ge_1−xSn_x layer is improved with increasing Sn content despite the increase in the lattice mismatch. This is caused by the shortening of the distance between the two dissociated partial dislocations, which indicates that the confinement of the stacking fault occurs at the Ge_1−xSn_x/Ge interface with increasing misfit strain.

An approach used to obtain a high-quality strain-relaxed SiGe layer by investigating the preferential aggregation and homogenization of nanometric bubbles along the B-doped Si_0.70Ge_0.30 interlayer in the H-implanted Si_0.75Ge_0.25/B-doped Si_0.70Ge_0.30/Si heterostructure has been proposed. The formation of nanometric bubbles is found to be closely correlated to the B atoms doped in the buried Si_0.70Ge_0.30 layer. Moreover, with the B-doped ultrathin Si_0.70Ge_0.30 interlayer, the formed nanometric bubbles can interact with dislocation loops and eject them by gliding to the Si_0.70Ge_0.30/Si interface. The threading dislocation density is 3.3 × 10⁵ cm⁻², which is superior to that of the sample grown with a graded buffer layer.

In this study, a BaTiO₃ (BT) nanocube assembly with metal–insulator–metal capacitor structure was fabricated by a dip-coating process. The BT nanocube assembly had relatively ordered structure after sintering. A high dielectric constant of approximately 3000 was achieved, with relatively low loss tangent. The enhanced dielectric properties of the nanocube assembled film were robust against thickness variation. We conjecture that the mechanism that enhanced the dielectric constant of the BT nanocube assembly is also contributed to by the effect of interfacial lattice strain between neighboring nanocubes.

Lead-free 0.96[Bi_1/2(Na_0.84K_0.16)_1/2(Ti_(1−x)Nb_x)O₃]–0.04SrTiO₃ (BNKTN–ST, with x = 0–0.030) ceramics were synthesized by a conventional solid-state reaction technique. Polarization and strain hysteresis loops indicated a significant disruption of ferroelectric order accompanied by an enhanced field-induced strain (S = 0.438%) with a high normalized strain S_max/E_max of 876 pm/V at 5 kV/mm. Their reproducibility was confirmed by the fabrication of a 10-layered stack-type multilayer actuator, which demonstrated a normalized strain S_max/E_max of 720 pm/V.

Self-heating effects in organic electronic devices are investigated by impedance spectroscopy (IS). A temperature modulation of the admittance couples the gigantic imaginary part of the capacitance to its small real part, which results in negative capacitance at low frequencies with high bias. We present a model to explain the effects and verify it experimentally for hole-only devices and organic light-emitting diodes. The negative capacitance widely observed in various electronic devices can be explained, at least in the organic electronic devices, by self-heating effects. The generic effects, which smear the device details, need to be eliminated to obtain IS signals that reflect the intrinsic device-specific properties.

In this work, we have developed a simple GaN-based microcavity (MC) with an intracavity shallow etched mesa. The textured GaN-based MC incorporated two high-reflectivity dielectric Bragg mirrors and an InGaN/GaN multiple quantum well with a shallow etched mesa as an optical confined structure. Lasing and transverse optical confinement characteristics have been verified by measuring devices with different mesa diameters. A quality factor (Q) of 2600 and a threshold energy of 30 nJ have been observed in a 10-µm-diameter device. Such a cavity structure could be implanted into electrically pumped GaN vertical-cavity surface-emitting lasers for supporting efficient transverse confinement.

Nonpolar a-plane ZnO-film and n-ZnO/i-ZnO/p-GaN heterostructure LEDs were grown epitaxially by pulsed laser deposition and metal–organic chemical vapor deposition on Si(001) using AlN and MnS as buffer layers. X-ray diffraction pole figures showed an epitaxial relationship of ZnO($11\bar{2}0$) ∥ AlN($11\bar{2}0$) ∥ MnS(001) ∥ Si(001). A near band-edge emission from ZnO was observed at 378 nm in photoluminescence measurements. Electroluminescence of nonpolar n-ZnO/i-ZnO/p-GaN LEDs displayed UV emission at 390 nm under forward and reverse bias. Successful growth of nonpolar n-ZnO/i-ZnO/p-GaN heteroepitaxial on Si provides an attractive solution for integrating nonpolar ZnO-based optoelectronic devices with Si substrates for various applications.

We have developed a yellow persistent phosphor of Ce³⁺–Cr³⁺-codoped Gd₃Al₂Ga₃O₁₂ transparent ceramics prepared by a solid-state reaction. The yellow persistent luminescence due to the Ce³⁺: 5d–4f transition was observed even after 460 nm blue-light excitation as well as after UV excitation. The chromaticity coordinate of the persistent luminescence in the ceramic phosphor is located at $(0.394,0.557)$, which appears really yellow compared with the color coordinate of the well-known SrAl₂O₄:Eu²⁺–Dy³⁺ or other conventional blue or green persistent phosphors. The luminance values for the transparent ceramic sample 1, 5, and 30 min after the blue excitation was ceased are 731, 63, and 8 mcd/m², respectively.

A new light-trapping-structure combined of diffraction grating and rear-located bilayer silver nanoparticles for thin-film silicon solar cells are theoretically investigated. By analyzing the absorption spectra and electric field intensity profiles, we find that the grating suppresses the reflection and results in the incident light angular redistribution, and that the rear-located bilayer nanoparticles fold light into the active layer. Furthermore, the grating and metal NPs are optimized and a short-circuit current density as high as 29.7 mA/cm² is obtained within a 1-µm-thick cell. In addition this design is applicable to silicon solar cells of various thicknesses.

To evaluate the X-ray-induced afterglow phenomenon, we developed an ionizing-radiation-induced luminescence characterization system equipped with a pulse-width-tunable X-ray source. The system consists of a pulse X-ray tube and a detector system based on photon counting. The excitation pulse width was tunable from nano- to millisecond ranges, and the dynamic range of the X-ray-induced afterglow was 10⁶. Conventional scintillators for X-ray CT or security systems, namely, Bi₄Ge₃O₁₂, CdWO₄, Tl-doped CsI, and Tb and Pr-codoped Gd₂O₂S, were evaluated for the performance test. Results show that the afterglow time profiles of these scintillators are consistent with generally known results with high accuracy.

An experimental technique for visualizing in-plane distributions of polarization states for an electromagnetic wave has been proposed and demonstrated successfully; distributions of rotating electric near-field vectors E_xy as well as their elliptic traces have been imaged electrooptically at a series of distances from the surface of a side-fed planar spiral antenna. The visualization was brought about by merging E_x and E_y phasor videos acquired complementarily by the live electrooptic imaging technique.

We achieve supercontinuum generation in the visible spectral regime through hollow beams in a two-mode photonic crystal fiber (TM-PCF). The TM-PCF is pumped with 532 nm sub-nanosecond pulses and it supports only the fundamental and second-order modes over the entire visible region. By two-mode excitation and nonlinear propagation, polychromatic hollow beams are generated in two separate spectral regions, which lead to a "white" hollow beam at the fiber output. We have also identified the efficient anti-Stokes conversion in the deeply normal dispersion regime as an intermodal phase-matched process, which can be employed for the blue extension of visible and ultraviolet supercontinuum.

For conventional imaging, the imaging resolution is determined by both the system's Rayleigh limit and the detector's pixel resolution. Even if the object's transmitted intensity is detected at the imaging plane with single-pixel detectors, we report that imaging beyond the Rayleigh limit can be achieved by exploiting both the object's sparsity in the representation basis and prior knowledge of the fixed optical system; this is supported by a numerical simulation and experiments. The image reconstruction algorithm is based on compressive sensing; factors affecting the reconstruction quality are also discussed.

The quadratic electro-optic effect in K_0.95Na_0.05Ta_1−xNb_xO₃ crystals near the Curie temperature was investigated. Both the electro-optic coefficients |R₁₁| and |R₁₂| decreased rapidly as the temperature increased beyond the Curie point. Interestingly, the ratio |R₁₁/R₁₂| increased. The polar nanoregions found in K_0.95Na_0.05Ta_1−xNb_xO₃ crystals near the Curie temperature are believed to be responsible for this effect. A phenomenological model is proposed to analyze the impact of these polar nanoregions on the quadratic electro-optic effect.

The X-ray detection capability of a scintillation detector equipped with a Cs₂ZnCl₄ single crystal was evaluated. The scintillation decay kinetics can be expressed as the sum of two exponential decay components. The fast decay component had a decay time constant of 1.8 ns, and its relative intensity was 95%. The total light output was 630 photons/MeV, and a subnanosecond timing resolution of 0.66 ns was obtained. The detection efficiency of 67.4 keV X-rays was 80% for a detector equipped with a 2.2-mm-thick Cs₂ZnCl₄ crystal. Thus, excellent timing resolution and high detection efficiency were achieved simultaneously.

Gain-switched operation of a double-core-waveguide semiconductor laser via traveling-wave optical pumping was achieved. An internal short pulse that traveled forward and backward in the cavity with amplification or decay was generated at high excitation power, and the pulse width and decay time constant of the main pulse were 5.5 and 2.6 ps, respectively; this decay time constant was shorter than the photon lifetime of the cavity or the limit predicted by standard rate-equation theory.

High-efficiency single-frequency compact master-oscillator power amplifiers (MOPAs) based on core-pumped highly Yb-doped phosphate fibers (YPFs), several centimeters long, are investigated theoretically and experimentally. By using numerical modeling and testing different YPF lengths to optimize the amplifier configuration, a stable output of more than 1.06 W, at 1014 nm, was measured experimentally from a MOPA laser, with a 4.0 cm long YPF. An optical-to-optical conversion efficiency of 81.4%, a typical net gain of more than 20.5 dB, and an output power per unit length of up to 265 mW/cm were obtained with this laser system. The measured optical signal-to-noise ratio of the MOPA laser is higher than 62 dB and the estimated laser linewidth is less than 20 kHz, without obvious broadening or degradation after amplification. There is excellent agreement between the results of the simulations and the experiments.

We investigated the high-frequency magnetic properties of oblique-sputtered CoFeBSm thin films. We found that the zero-field ferromagnetic resonance frequency f_r can be tuned from 3.8 to 6.4 GHz by rotating the samples within the plane. The angular tunable f_r is tentatively explained with the competition of uniaxial anisotropy (arising from the oblique deposition) the rotatable anisotropy (originating from the rotatable stripe domain). These results may have great implications for tunable microwave magnetic devices.

The effects of inserting an amorphous FeZr layer between the [Pt/Co] multilayer and the CoFeB/MgO layer in stacks possessing perpendicular magnetic anisotropy are examined. A 1-nm-thick FeZr layer is effective in forming a bcc (001)-textured CoFe layer during annealing by suppression of crystallization at the interface with the multilayer, which is terminated in a close-packed plane. Because FeZr is magnetic, it has an advantage over Ta, an alternative material used for the same purpose. Efficient magnetic coupling between the multilayer and CoFeB/MgO occurs even for large FeZr layer thicknesses, so the magnetic properties of the stack are only weakly affected.

Pseudo-single-crystal γ'-Fe₄N films were fabricated by changing the degree of order (S) of N sites, and their anisotropic magnetoresistance (AMR) effects along the Fe₄N[100] direction were investigated. Negative AMR ratios were observed in all the specimens in the temperature range of 5–300 K. Specific features — a marked increase in the AMR magnitude below 50 K and the appearance of the cos 4θ term in the AMR curve below 30 K — were clearly observed in the case of high S, and these features decreased with decreasing S. The physical origin of these features is proposed to be a crystal field effect on the AMR.

A magnetic field is predicted to emerge on a particle in a rotating material body even if the body is electrically neutral. This emergent field is called a Barnett field. We show that nuclear magnetic resonance (NMR) enables direct measurement of the Barnett field in solids. We rotated both a sample and an NMR coil synchronously at high speed and found an NMR shift whose sign reflects that of the nuclear magnetic moments. This result provides direct evidence of the Barnett field. The use of NMR for Barnett field measurement enables the unknown signs of nuclear magnetic moments in solids to be determined.

We report on the oscillation behavior of spin torque oscillators having a perpendicularly magnetized free layer and in-plane magnetized reference layer as a function of bias field angle. The measurement results show that both emission power and oscillation frequency are strongly dependent on the bias field angle. When the bias field was tilted by only a few degrees away from the axis normal to the film toward either parallel or antiparallel configuration, the power increased by about 1.5 times or decreased by two orders of magnitude, and the peak frequency varied by about ±1 GHz.

Coverage-dependent magnetic properties of Ni ultrathin films on Pd(001) was investigated using X-ray magnetic circular dichroism (XMCD). Magnetization curves and Ni L_2,3 XMCD spectra were measured as a function of Ni coverage. These results revealed a spin reorientation transition from in-plane to out-of-plane as the Ni coverage increased. Ni 3d spin and orbital magnetic moments were evaluated using the magneto-optical sum rules. The presence of a magnetic dead layer inside the Ni film explains the Ni coverage dependence of spin magnetic moment.

Magnetization reversal in a GaMnAs film grown on a Si substrate was investigated using planar Hall effect measurements. The angular dependence of the planar Hall resistance (PHR) shows that cubic crystalline anisotropy along the $\langle 100\rangle$ directions dominates the film's magnetic anisotropy. However, the magnetization reversal behavior varies significantly with the applied field strength: as the magnetic field strength decreases, the PHR amplitude decreases, and hysteresis appears in data obtained with clockwise and counterclockwise rotation of the field directions. Furthermore, asymmetry in the PHR amplitude between the two opposite field directions appears during the angle scan and increases with decreasing field strength. We show that these features arise from a broad distribution of magnetic domains having different pinning fields.

We report the switching of a magnetic vortex core in ferromagnetic elliptical disks induced by a nanosecond field pulse. We show that the switching probability depends on both the duration and amplitude of the field pulse. The minimum magnetic field required for the core switching depends also on the ellipticity of the disk. Micromagnetic simulations reproduce this behavior and reveal that there are two mechanisms of the core switching.

Microwave oscillation properties of spin torque vortex oscillators (STVOs) consisting of an FeB vortex free layer were investigated. Because of a high MR ratio and large DC current, a high emission power up to 3.6 µW was attained in the STVO with a thin FeB free layer of 3 nm. In STOs with a thicker FeB layer, e.g., 10 nm thick, we obtained a large Q factor greater than 6400 while maintaining a large integrated emission power of 1.4 µW. Such excellent microwave performance is a breakthrough for the mutual phase locking of STVOs by electrical coupling.

We investigate the magnetization dynamics in synthetic antiferromagnetic (SyAFM) Fe/[Co/Cu]₁₀/Co/Pt multilayers using the microwave rectifying effect. We observe two distinct resonant modes in the dynamics. Numerical simulations reveal that the resonant modes can be attributed to acoustic and optical modes, which are the characteristic resonant modes of antiferromagnetically coupled materials. It is found that the linewidth of the optical mode is larger than that of the acoustic mode by a factor of 5. This broadening of the linewidth in the optical modes can be explained by the mutual spin pumping effect between the magnetizations precessing out of phase.

We synthesized superconducting cuprates with square-planar coordinated copper, i.e., Nd₂CuO₄ and infinite-layer structures, by molecular beam epitaxy. The normal and superconducting states were scrutinized by resistivity and Hall measurements. The low-temperature Hall coefficients are positive regardless of doping in the absence of antiferromagnetic-induced band folding, and the effect of doping on electronic correlations is associated with band filling with a common topology of the Fermi surface implied, where the Fermi volume scales with doping level x.

Anisotropic superconducting properties including the upper critical field H_c2, thermal activation energy U₀, and critical current density J_c are systematically studied in a large Ca_1−xLa_xFeAs₂ single crystal (x ∼ 0.18). The obtained H_c2 bears a moderate anisotropy γ of approximately 2–4.2, located between those of "122" Ba_1−xK_xFe₂As₂ (1 < γ < 2) and "1111" NdFeAsO_1−xF_x (5 < γ < 9.2). Both the magnitude of U₀ and its field dependence are very similar to those of NdFeAsO_1−xF_x, also indicating anisotropic superconductivity. Moreover, high and anisotropic J_c's exceeding 10⁵ A/cm² have been calculated from the magnetization hysteresis loops, indicating the existence of strong bulk-dominated pinning in the present superconducting material.

Densely arraying gold nanoparticles (AuNPs) immobilized on substrates is still a challenge. For the arraying, surface modification of AuNPs with alkanethiols is a key technology. However, if the particle size is larger than 20 nm, short-chain alkanethiols have very weak interparticle interaction such that self-assembly is not realized, whereas long-chain alkanethiols have very strong interaction such that self-aggregation is induced in solution. One solution is their combination. Eventually, a $\text{HexT}:\text{DodT} = 4:1$ mixture gave a dense array of 55 nm AuNPs on an ITO substrate with a coverage of approximately 80%. Our approach provides high-performance plasmonic optics with a resonance wavelength of more than 700 nm.

The electron and hole g-factors in individual InAs/GaAs quantum rings were evaluated using the bistable responses of the optically induced nuclear spin polarization. Although the dispersions of the hole and exciton g-factors were larger than that of the electron g-factor in the individual quantum rings, a strong correlation between the hole and exciton g-factors was clearly observed. Part of the dispersion of the measured hole g-factor was explained well by considering the effect of strain-induced valence band mixing.

Arrays of single-crystalline aluminum nitride nanotubes (AlNNTs) were successfully synthesized at 780 °C by a facile CVD method without templates or catalysts. Faceted hexagonal AlNNTs with diameters from tens to hundreds of nanometers were observed. 264 nm deep-ultraviolet emission associated with Al vacancies was detected by photoluminescence. Raman characterization indicates that the lattice of the AlNNTs is notably defective, and disorder-activated silent B₁ (low) and B₁ (high) were detected at 583.0 and 730.0 cm⁻¹ respectively, which were allowed by the breakdown of the translational crystal symmetry. The redshift of E₂ (high) Raman modes indicates that biaxial tensile stress exists in the samples.

Graphene is a promising material for next-generation devices owing to its excellent electronic properties. Graphene devices do not, however, exhibit the high performance that is expected considering graphene's intrinsic electronic properties. Operando, i.e., gate-controlled, photoelectron nanospectroscopy is needed to observe electronic states in device operation conditions. We have achieved, for the first time, pinpoint operando core-level photoelectron nanospectroscopy of a channel of a graphene transistor. The direct relationship between the graphene's binding energy and the Fermi level is reproduced by a simulation assuming linear band dispersion. This operando nanospectroscopy will bridge the gap between electronic properties and device performance.

Carbon nanotubes (CNTs) are an attractive material for flexible thermoelectric devices because of their mechanical strength, lightness, and high conductivity. However, their thermoelectric performance is restricted by their large thermal conductivity. In this letter, a novel material design for improving the performance of CNTs by inserting biobased molecules at CNT/CNT junctions is proposed. We demonstrate that the thermal conductivity is markedly suppressed, but the electrical conductivity is increased by the addition of cage-shaped proteins with semiconducting cores. The Seebeck coefficient also increases by selecting the appropriate core material. By improving the three above-mentioned important parameters, the ZT value is increased over 1000-fold.

Metallic nanoparticles with controllable plasmonic properties were fabricated by a laser-induced transfer technique. By controlling the laser fluence and the number of laser pulses, nanostructures with complementary plasmonic properties were produced. The plasmonic properties of the nanostructures were controllably modified by changing the number of irradiation pulses. This technique not only manipulates the plasmonic response of metallic nanoparticles but also facilitates the versatile transfer of metallic nanostructures onto fiber tips and stretchable substrates. This reproducible method is fast, inexpensive, flexible, and suitable for various applications for plasmonic devices.

Universal conductance fluctuations (UCFs) are extracted in the magnetoresistance responses in bulk-insulating Bi₂Te₂Se microflakes. Their two-dimensional character is demonstrated by field-tilting magnetoresistance measurements. Their origin from the surface electrons is determined by the fact that the UCF amplitudes remain unchanged while applying an in-plane field to suppress the coherence of bulk electrons. After considering the ensemble average in a batch of micrometer-sized samples, the intrinsic UCF magnitude of over 0.37 e²/h is obtained. This agrees with the theoretical prediction on topological surface states. All the lines of evidence point to the successful observation of the UCF of topological surface states.

We report a marked reduction in the dislocation density of a 4H-SiC crystal using a high-efficiency dislocation conversion phenomenon. During the solution growth, threading dislocations were efficiently converted to basal plane defects by the step flow of macrosteps. Utilizing this dislocation conversion phenomenon, we achieved the marked reduction of threading dislocation density. Consequently, the threading screw dislocation density was only 30 cm⁻², which was two orders of magnitude lower than that of the seed crystal. The 4H-SiC polytype of the seed crystal was replicated in the grown crystal, which was attributed to the spiral growth owing to a few remaining threading screw dislocations upstream of the step flow.

By employing computational simulations and experiments, we explore the potential for fast, high-quality 4H-SiC crystal growth using a high-temperature gas source method. Appropriate temperature ranges for obtaining high growth rates in H₂ + SiH₄ + C₃H₈ + HCl and H₂ + SiH₄ + C₃H₈ gas systems are examined computationally. Experimental results show that an increase in the gas flow velocity enhances the crystal growth rate, and high growth rates of >1 and >2 mm/h are obtained using the H₂ + SiH₄ + C₃H₈ + HCl and H₂ + SiH₄ + C₃H₈ gas systems, respectively. Single crystal growth that retains the low threading screw dislocation density of the seed crystal is accomplished, even at very high growth rates of >2 mm/h.

Dark line defects arising from dislocations in epitaxial CdTe films are known to strongly limit the overall performance of optoelectronic devices. However, their effect on carrier diffusion length and lifetime in the material immediately surrounding dislocations is not well quantified. We apply a photoluminescence imaging technique to directly measure these parameters in a CdTe/MgCdTe double heterostructure. Radiative recombination is reduced by up to 85% within 5 µm of the dislocation. Additionally, the carrier diffusion length and lifetime decrease by ∼50 and ∼80%, respectively.

To improve the passivation effect at a-Si:H/c-Si interface in heterojunction (HJ) solar cells, ultrathin SiO_x layers with a thickness of approximately 2 nm were pre-formed on c-Si surfaces in chemical solutions. It was demonstrated that the SiO_x layers pre-formed in hot de-ionized water and hydrochloric acid solutions improve effective carrier lifetime, and it is further enhanced through a post annealing process. When the thin SiO_x layers were applied to HJ solar cells, increase in both V_oc and J_sc was achieved, implying the improved interface quality for these HJ solar cells, as compared with the reference without the SiO_x layer.

This paper reports on AlN epilayers with improved crystalline quality grown on silicon-on-insulators (SOIs) by plasma-assisted molecular beam epitaxy (PAMBE). The influences of the substrate on threading dislocation (TD) and surface morphology have been investigated. Two sets of wafers were grown on Si and SOI substrates with the same optimized growth parameters. An atomically smooth AlN epilayer was realized on an SOI substrate with reduced TD density compared to that on Si. This result is attributed to the stress release effect due to the lattice distortion in the top silicon layer of the SOI substrate.

Laser Thomson scattering has been applied to a nonequilibrium atmospheric plasma in contact with an ionic liquid to measure both electron density (n_e) and electron temperature (T_e). The discharge plasma was produced between a needle and a plane ionic-liquid electrode separated by a 3 mm gap. In comparison with a conventional metal electrode, distinct differences were found in spatial profiles of n_e and T_e of the plasma produced with the ionic-liquid electrode.

The temperature (T) dependence of the sodium ion diffusion coefficient D of a Na_xMnO₂ thin film is extensively investigated versus x and T using electrochemical impedance spectroscopy. D is found to be 5.0 × 10⁻¹¹ cm²/s at x = 0.54 at 301 K, which is much larger than the value of 0.7 × 10⁻¹¹ cm²/s at x = 0.54 at 303 K of a Na_xCoO₂ thin film. In addition, the activation energy $E_{\text{a}}^{D}$ of D (= 0.26–0.32 eV) is smaller than that of Na_xCoO₂ (= 0.31–0.44 eV). The improved Na⁺ diffusion properties of Na_xMnO₂ are interpreted in terms of the larger interlayer distance (d = 5.54 Å) of Na_xMnO₂.

A novel photoexcitation method for the light-addressable potentiometric sensor (LAPS) is proposed to achieve a higher spatial resolution of chemical images. The proposed method employs a combined light source that consists of a modulated light probe, which generates the alternating photocurrent signal, and a ring of constant illumination surrounding it. The constant illumination generates a sheath of carriers with increased concentration which suppresses the spread of photocarriers by enhanced recombination. A device simulation was carried out to verify the effect of constant illumination on the spatial resolution, which demonstrated that a higher spatial resolution can be obtained.

The tunneling effects of acoustics have been found when the proposed solid–fluid superlattices (SLs) are used to match two fluids with a large impedance mismatch. One of the examples shows that, by embedding a rubber/water SL between air and crude oil, the transmission of acoustic energy reaches 0.97 at 5° at 8.73 kHz. According to the results of theoretical analyses and full-wave simulations, this energy tunneling is attributed to the acoustically resonant states induced by the SL at the interface. The tunneling frequencies can be tuned in real time by varying the interspacing between the solid layers of the SL, which may have wide potential applications in matching two fluids, such as acoustic coupling between air and crude oil during petroleum exploration.