We demonstrate the power enhancement of planar-type uni-leg poly-Si thermoelectric generators by nano-patterning. The thermoelectric generators were fabricated on an SOI wafer by a conventional lithography-based process. The size of the phononic nano-patterning (300 nm in period) was designed based on the thermal phonon mean free path spectrum. The thermal conductivity of the Si membrane was reduced

A low-temperature-grown GaAs (LTG-GaAs) terahertz (THz) photoconductive antenna device with layer structure consisting of doped buffer demonstrated enhanced emission intensity and detection sensitivity. As THz emitter, a 116% increase is exhibited by the LTG-GaAs with doped buffer relative to its undoped counterpart at 9 V bias and 0.8 mW pump power with spectral distribution extending to ∼3 THz. As a

We fabricated BaSi 2 films on Si substrates at 600 °C by sputtering under various radio-frequency powers ( P BaSi2 ). Rutherford backscattering spectrometry revealed that the atomic ratio of Ba and Si reaching the substrate remained unchanged regardless of P BaSi2 . However, the photoresponsivity decreased with P BaSi2 . This is ascribed to the increase of vacancy-type defects from the peak shift of

Dispersion properties of compact single- and double-side grooves SSPPs are analyzed and compared. The combination of two single-side grooves with opposite phases can sustain the odd-mode SSPPs, which is contrary to the dominantly even mode SSPPs existed on metal-dielectric interfaces in optical frequencies or on structured metal surfaces in the lower frequencies. Two low-pass filters based on odd-mode

We studied magnetic tunnel junctions (MTJs) with a MgO(001) barrier and metastable bcc Co 3 Mn(001) disordered alloy electrodes. A tunnel magnetoresistance (TMR) ratio was approximately 200%–250% observed at room temperature. We successfully observed the TMR ratio greater than 600% at 10 K which was higher than the past reported value of MgO-based MTJs with ultrathin bcc Co(001) electrodes. However

Transmission extreme ultraviolet microscopy is applied to the staining-free observation of a poly(styrene–methyl methacrylate) (PS/PMMA) blend. At a photon energy of 92 eV, the imaginary part of the atomic scattering factor for oxygen, which represents the absorption, is four-times larger than that of carbon, and microstructures can be visualized by the contrast resulting from the presence of oxygen

We report the enhancement of Pt-coated silicon micropore X-ray optics using plasma atomic layer deposition (ALD). High-aspect-ratio micropores of width20 μ m and depth300 μ m were coated with ∼20 nm Pt and ∼10 nm Al 2 O 3 . The estimated surface roughnesses, determined from X-ray reflectivity curves for Al K α 1.49 keV radiation, were ##IMG## [http://ej.iop.org/images/1882-0786/13/8/087001/apexaba7a5ieqn1

The photoluminescent of carbon dots (CDs) was significantly quenched when CDs were densely deposited on glass substrates, which limited their applications. In this work, the luminescent enhancement of blue CDs with polymer of polyvinylpyrrolidone (PVP) is explored by coupling with an “Island” Ag film. The fluorescence intensity of CDs enhances nearly 5-fold. Furthermore, the application of Ag/CDs/PVP

We demonstrate strong coupling between a single quantum dot (QD) and a GaAs-based L4/3-type photonic crystal nanocavity. The L4/3 cavity supports a high theoretical Q factor (∼8 × 10 6 ), a small mode volume [∼0.32 ( λ / n ) 3 ], and an electric field distribution with the maximum electric field lying within the host dielectric material, which facilitates strong coupling with a QD. We fabricated L4/3

An energy-dispersive X-ray spectrometer using a transition-edge sensor microcalorimeter with a scanning transmission electron microscope was applied to detect low concentrations of phosphorus (P) in an Fe–P–Mo–Mn alloy. The high energy resolution of 7.2 ± 0.9 eV was demonstrated in the measurements of P K α signals, which were not visible in the spectra for a conventional silicon drift detector. The

Hyperparallel quantum information processing outperforms its traditional parallel one in terms of channel capacity, low loss rate, and processing speed. We present a way for implementing a robust hyperparallel optical controlled-phase-flip gate through microcavities. The gate acts on polarization and spatial degrees of freedom simultaneously, and the incomplete and undesired interactions between photons

We investigated the gate voltage dependence of T c in electrochemically etched FeSe films with an electric-double layer transistor structure. The T c zero value of the etched FeSe films with a lower gate voltage ( V g = 2.5 and 3.3 V) reaches 46 K, which is the highest value among almost all reported values from the resistivity measurements except for the data by Ge et al. This enhanced T c remains

This letter describes a theoretical and experimental study of an underwater acoustic Luneburg lens made of isotropic metamaterial. The designed lens is found to be capable of focusing plane waves over a broad range from 160 to 210 kHz. The measured lateral width of the focal spot is 5.5 mm, an ideal size that is close to the Rayleigh resolution limit. The functionality of the underwater lens is realized

Diffusion in a magnesium (Mg)-implanted homoepitaxial GaN layer during ultra-high-pressure annealing (UHPA, in ambient nitrogen, under 1 GPa) was investigated. Annealing at 1573 K resulted in Mg-segregation at the edge of the implanted region, which was suppressed using a higher temperature of 1673 K. Hydrogen (H) atoms were incorporated during the UHPA, resulting in the Mg and H developing the same

Perfect absorption is key to achieving high responsivity of a thin-film photodetector. Here, we report the effect of a metamaterial perfect absorber (MPA) on the external quantum efficiency (EQE) of plasmonic photo-thermoeletric conversion, which is a photodetection method based on local heating. The photodetector with a MPA shows strong absorption, resulting in EQE about three times of that of a control

The simplicity of light-emitting electrochemical cells (LECs) offers the potential ability for printed electronics. However, the designs of current LECs are limited and require fine control of the active/metal layers, which hampers their applicability. Here, we propose a versatile LEC structure that is easily prepared by laminating plastic films and drop-casting organic solutions. This simple fabrication

We recently invented a method called the flux-film-coated technique for purifying a GaN wafer with low dislocation density grown from point-seed crystals. In this study, we investigated the mechanism behind the reduction of dislocation density in the GaN wafer by evaluating the three-dimensional behavior of dislocations using multiphoton-excitation photoluminescence images. We made the surprising discovery

We report epitaxial growth and properties of n-type ferromagnetic semiconductor (FMS) (In,Fe)As (Fe 6%) co-doped with Mn at different concentrations x ( x = 0.4%, 0.8%, 2%, 4%, 8%). The electron concentration n of (In 0.94− x ,Fe 0.06 ,Mn x )As decreases as x increases, leading to the decrease of Curie temperature ( T C ) as expected for electron-induced ferromagnetism. However, ferromagnetism is still

He discharge in a coaxial dielectric barrier discharge (DBD) device develops in three stages: first, a Townsend-glow-type plasma spreads in the region between the electrodes; second, a plasma bullet (streamer type discharge) propagates axially and; third, the bullet transitions into a surface discharge at the dielectric surface. These mode transitions are quite different from planar type DBD, in which

By first-principles calculations, we report the computational design of a molecular transistor that is gated by exploiting the van der Waals (vdW) interactions between molecules. The proposed device is constructed by sandwiching between two gold electrodes with one coronene molecule bonded to the other free one via vdW interactions. We demonstrate that the vdW interactions play a role very similar

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We report the electrical and optical properties of gallium nitride grown by halogen-free vapor phase epitaxy (HF-VPE). The electron mobility of the HF-VPE-GaN layers was found to be comparable to or better than the GaN layers obtained using MOCVD. The positron annihilation spectroscopy analyses revealed that the density of the electroneutral or negatively charged vacancy-type defects in the HF-VPE-GaN

We have proposed a novel nano-height cylindrical waveguide in blue GaN-based vertical-cavity surface-emitting lasers (VCSELs). The proposed 5 nm step height cylindrical waveguide using simple processes provides lateral optical confinement and excellent performance in terms of light output power (LOP) and wall plug efficiency (WPE). A fabricated multi-mode VCSEL with 7 μ m emission diameter achieved

GaN crystal with 4.2 mm thickness and size lager than 2 inch without cracks and pits was realized by hydride vapor-phase epitaxy (HVPE) on an acidic ammonothermal (SCAAT TM ) seed. The average threading dislocation (TD) density was as small as 1.4 × 10 3 cm −2 . Multi-photon excitation photoluminescence revealed that complete one-to-one correspondence of TD at the interface between the seed and epilayer

We investigated the effect of forming gas annealing (FGA) on the electrical properties of SiO 2 /GaN MOS devices. We conducted systematic capacitance–voltage measurements on metal-oxide-semiconductor structures and observed a significant amount of anomalous positive fixed charge (3 × 10 12 cm −2 ) at the interface between SiO 2 and GaN for FGA temperatures over 250 °C. The fixed charges generated by

We investigate the nonequilibrium energy transport across a graphene-based unconventional superconductor (SC) hybrid structure with a barrier region sandwiched between normal and superconducting regions, which is evaluated within an extended Dirac Bogoliubov-de Gennes formalism. Three different scenarios of the hybrids having p -wave triplet SCs with (i) p x -, (ii) p y -, and (iii) unitary chiral

We present the first-principles calculations of lithium-intercalated diamond-like boron compounds LiB and LiB 2 . Although the pristine diamond structure of boron is dynamically unstable, LiB has no imaginary phonon mode after lithium intercalation. Our calculations show that LiB is an insulator with a direct energy gap of 1.45 eV. By removing a face-centered cubic sublattice of lithium from LiB, a

We report the growth of YF 3 epitaxial thin films by magnetron sputtering using MgF 2 (100) substrates as a fluorine source instead of fluorination gases. We find that the substrate selection based on the relative film/substrate Gibbs free energies of formation can drive F-ion diffusion from the fluoride substrates into the Y thin films. Due to the high diffusivity of F ions in YF 3, this method can

Epitaxial strain engineering of luminescent properties in ZnGa 2 O 4 :1%Mn thin films was demonstrated by changing both the O 2 gas pressure in the deposition chamber and the film thickness. Films were prepared under pressures of 0.2 and 100 mTorr. While, for low-pressure films, the residual strain was constant, for high-pressure films, it relaxed as the thickness of the film increased. Emission spectra

To augment the magnetoresistance (MR) ratio of n-type non-degenerate Si-based lateral spin valves (Si-LSVs), we modify the doping profile in the Si layer and introduce a larger local strain into the Si channel by changing a capping insulator. The highest MR ratio of 1.4% is achieved in the Si-LSVs through these improvements, with significant roles played by a reduction in the resistance-area product

A closed-cell metamaterial absorber (CCMA) made of a low-permittivity dielectric is proposed and investigated in this paper. It realizes five absorption peaks below −10 dB in the range of 6–18 GHz, and the strongest absorption can reach near −40 dB. By investigating the distribution of electromagnetic fields, it is found that multi-resonance is caused by the embedding of closed cells. Interestingly

Extremely flat, two-bilayer-high Bi(110) film was grown on a Si(111)√3 × √3-B substrate by two-step growth. Round amorphous islands nucleated during the initial deposition of Bi atoms at 90 K. The islands became larger and transformed into atomically flat, two-bilayer-high Bi(110) islands at a critical size (40 nm 2 ) in subsequent annealing. The Bi(110) islands extended laterally, and the substrate

Spin–orbit torques (SOTs) acting in a Py/Pt/Co tri-layer, where the Py and Co layers are in-plane and perpendicularly magnetized, respectively, are investigated via the ferromagnetic resonance method. The resonance linewidth of the Py layer is clearly modulated by the DC bias current due to the damping-like SOT originated from the spin Hall effect in the Pt. In addition to this, the linewidth modulation

To clarify the existence of cation vacancies in Ce-doped Gd 3 Al 2 Ga 3 O 12 (Ce:GAGG) scintillators, we performed gamma-ray-induced positron annihilation lifetime spectroscopy (GiPALS). GiPALS spectra of GAGG and Ce:GAGG comprised two exponential decay components due to positron annihilation at bulk and defect states. By an analogy with Ce:Y 3 Al 5 O 12 , the defect-related component was attributed

An external electric field (EEF) was applied to regulate perovskite crystal growth in order to achieve the preferred crystallization. The out-of-plane and in-plane crystallization of MAPbI 3-x Cl x , MAPbI 3 and Cs 0.05 (FA 0.83 MA 0.17 ) 0.95 Pb(I 0.83 Br 0.17 ) 3 perovskites was compared based on the grazing incidence X-ray diffraction technique. The results showed that vertical EEF stretches the

A distributed acoustic sensing with digital differential coherent optical time-domain reflectometry based on heterogeneous dual-sideband linear frequency-modulated (LFM) pulse is proposed. The positive and negative LFM signals are loaded on the upper and lower optical sidebands respectively. The loaded signals with the same spectrum width but opposite slope chirps will result in an opposite interference

Binary compounds, fully B-/C-/N-substituted germanenes, exhibit the diversified phenomena through the different chemical bondings. The delicate first-principles calculations can present the buckling/planar honeycomb lattices, the atom-dominated band structures, the spatial charge densities, the spin density distributions, and the atom-, orbital- and spin-decomposed density of states, being very useful

The capped Si expels completely the Ge dimers on top of the epi Ge(001)-2 × 1 and exhibits a multiphase electronic structure consisting of strained surface atoms bonded with Ge in the film. The deposition of molecular oxygen at room temperature removes a portion of the segregated Ge atoms and oxidizes some of the rest. The surface Si atoms exhibit 1+ to 4+ charge states. Heat eliminates the embedded

Brillouin optical correlation-domain reflectometry (BOCDR) generally suffers from the trade-off relationship between the spatial resolution and the measurement range. In this work, we perform a proof-of-concept demonstration of a chirp modulation scheme to extend the measurement range of BOCDR. In this scheme, optical frequency is modulated using a chirp-shaped waveform. We show that, although the

In this paper, a dimethyl sulfoxide (DMSO) bathed poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS, 1:1.25) film served as the transparent conductive layer (TCL) and the undoped PEDOT:PSS (1:6) film was used as the hole transport layer (HTL) of methylammonium lead iodide (MAPbI 3 ) perovskite solar cells (PSCs). Optimal performances (i.e. an open circuit voltage of 0.67 V, a short

We report a novel graphene oxide derived nanomaterial, carboxyl graphene oxide (GO-COOH) based saturable absorber (SA) for ultra-short pulse generation. Our GO-COOH based SA demonstrates a large modulation depth of 11.4% and a low saturation intensity of 31.12 MW cm −2 . The output pulse width is ∼398 fs with a spectral bandwidth of ∼7.45 nm. Stable bound state solitons are also generated with the

We fabricated randomly oriented polycrystalline BaSi 2 films on TiN metal layers by sputtering for the deployment of BaSi 2 solar cells on a flexible substrate. The formation of BaSi 2 films was demonstrated by X-ray diffraction and Raman spectroscopy. Photoresponsivity increased at wavelengths <1000 nm, corresponding to the band gap of BaSi 2 , and reached 1.6 A W −1 at a wavelength of 650 nm under

In this study, surface plasmon-enhanced nanolasers beyond the optical diffraction limit with different structural parameters have been designed and analyzed to optimize the surface plasmon coupling efficiency. Electric field energy can be highly confined in the ultrathin insulating region, as revealed via simulated distribution of the electric field using COMSOL Multiphysics software, resulting in

We theoretically propose a compound metasurface structure consisting of a patterned black phosphorus (BP) sheet sandwiched by dielectrics, which can achieve a tunable plasmon-induced transparency (PIT) effect in the mid-infrared region. The PIT effect can be actively adjusted by changing the geometric parameters and the carrier concentration of BP. The mechanism of PIT originates from the near-field

We demonstrate the excellent hole-transporting ability of molybdenum disulfide (MoS 2 ) by applying one-dimensional (1D) and two-dimensional (2D) mixed MoS 2 -single-walled carbon nanotube (MoS 2 -SWCNT) heterostructures to perovskite solar cells. The CVD-synthesized MoS 2 -SWCNT functions as both the hole transport layer and anode at the same time. Compared with bare SWCNT, the wrapping of 1D/2D MoS

We demonstrated double-layered epitaxial lateral overgrowth of α -Ga 2 O 3 by halide vapor phase epitaxy. The second ELO α -Ga 2 O 3 were regrown epitaxially and selectively through the windows of the patterned masks which were prepared on an ELO α -Ga 2 O 3 . The ELO islands coalesced step-by-step due to the nested-structure mask pattern. No threading dislocation was found by TEM not only above the

Low dislocation density and low-resistance GaN wafers are in high demand for improving the performance of vertical GaN power devices. Recently, GaN wafers with the dislocation density of 8.8 × 10 4 cm −2 and the resistivity of 7.8 × 10 −4 Ω cm, were fabricated using oxide vapor phase epitaxy (OVPE). In this study, GaN p–n diodes on GaN wafers prepared by the OVPE method were evaluated for verifying

We propose a method to control the skyrmion motion in an angelfish-type racetrack composed of triangular regions of reduced magnetic anisotropy using an alternating current (AC) magnetic field with nanosecond ordering. The method is verified in micromagnetic simulations from which we found that the maximum velocity of the skyrmion is 11 m s −1 . Moreover, the direction the skyrmion moves can be reversed

Relevant experiments have shown that more than 90% of photo-generated carriers can escape from multiple quantum wells (MQWs) sandwiched between p-type and n-type layers (a PIN structure). The escape time of the photo-generated carriers is on the femtosecond scale, much less than their relaxation time. In contrast, photo-generated carriers cannot escape from MQWs sandwiched between two n-type layers

Understanding the timing and location of nanoparticle (NP) generation during pulsed laser ablation in liquid is important for their fabrication. We report on high-speed videographic observations of UV-induced photoluminescence from YVO 4 :Eu 3+ NPs following laser ablation in water. YVO 4 :Eu 3+ is a red-emitting phosphor under UV excitation. A white mist-like region of low brightness, thought to be

A dual-band polarization reconfigurable terahertz antenna is proposed by incorporating a monopole antenna with a graphene-based dual-band active polarization converter metasurface (APCM). The APCM unit cell adopts two perpendicular slots on the top and two biased graphene patches on the bottom, which can be switched from ON (polarization conversion) to OFF (polarization maintain) in dual-band by adjusting

A metal–dielectric layered structure (silver layer and fluorescein–polyvinyl alcohol composite layer) was used in a reverse Kretschmann configuration to observe plasmon-coupled emission tuning (PCET) and emission enhancement. An emission peak shift of nearly 100 nm within an angle tuning range of 4.5° and a nearly 20-fold emission enhancement were observed. Biosensitivity can thus be increased by mapping

Aluminum gallium nitride (AlGaN)-based ultraviolet-B band laser diodes (LDs) with a p-type AlGaN cladding layer using polarization doping were fabricated on lattice-relaxed Al 0.6 Ga 0.4 N/AlN/sapphire. The threshold current density J th and lasing wavelength of this LD were 25 kA cm −2 and 298 nm, respectively. The internal loss ( α i ) was estimated by means of a variable stripe length method using

The origin of E3 electron traps at E C –0.58 eV in GaN was investigated using Si-doped n-type GaN layers grown on freestanding GaN substrates using MOVPE. These layers contained impurity Fe at various concentrations depending on the growth conditions and the position within the wafer. Twenty E3 concentrations ( N T,E3 ) determined by deep-level transient spectroscopy were plotted against the corresponding

We present a high-speed multi-beam X-ray imaging realized using a detector system and the recently developed multi-beam X-ray optics [Voegeli et al., Optica 7 , 514 (2020)]. The detector utilized optical relay lenses and mirrors for connecting four scintillator screens to a CMOS camera, enabling the high-speed simultaneous acquisition of multiple projection images. We successfully acquired nine projection

The performance of photodetectors based on monolayer transition-metal dichalcogenides (TMDCs) varies greatly, even for the same type of devices made of the same material. Here, we compared the performance of phototransistors based on monolayer MoS 2 grown by chemical vapor deposition (CVD) with different seeding promoters of perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt (PTAS), copper

Strain-induced phenomena in graphene strongly depend on the strain direction with respect to the crystallographic orientation of graphene. The conventional method for determining the strain direction in graphene uses the polarized Raman spectroscopy of the G band and needs accurate alignment of the polarizer angle, which is not easy in a conventional Raman microscope equipped with a simple sample stage

This work presents self-focusing 3D lithography based on the refractive index changes of polyethylene glycol diacrylate (PEGDA) during photopolymerization. Since the polymerization of PEGDA leads to an increase in the refractive index, the UV light rays in the PEGDA undergo a refraction effect during exposure, thus being focused and forming 3D photopolymerized structures. We demonstrate the potential

A photoconductive gain (up to 400%) is observed in a 4-hydroxycyanobenzene (4HCB, C 7 H 5 NO) bulk organic semiconducting detector, resulting in a high sensitivity of38.8 μ C Gy air −1 s −1 cm −2 under 50 kVp X-ray beam irradiation. The gain variation tendency as the function of both the applied bias voltage and the incident X-ray dose rate is revealed. A rising stage at the gain versus dose rate curve