-
Field-free magnetization switching with full scale in Pt/Tm3Fe5O12 bilayer on vicinal substrate Appl. Phys. Express (IF 2.3) Pub Date : 2024-03-15 Tianhui Li, Weikai Luo, Jinxiang Wu, Xinjun Li, Hui Yang, Xiaotian Zhao and Hongyu An
The spin–orbit torques within a Pt/Tm3Fe5O12 (TmIG) bilayer offer an expedient method for manipulating the magnetization of TmIG. However, the practical application of TmIG is hindered by the presence of an external field during switching. Here, we demonstrate field-free magnetization switching in Pt/TmIG bilayer on a vicinal substrate with minimal sacrifice to the perpendicular magnetic anisotropy
-
Realizing reliable linearity and forming-free property in conductive bridging random access memory synapse by alloy electrode engineering Appl. Phys. Express (IF 2.3) Pub Date : 2024-03-15 Ao Chen, Puyi Zhang, Yiwei Zheng, Xiaoxu Yuan, Guokun Ma, Yiheng Rao, Houzhao Wan, Nengfan Liu, Qin Chen, Daohong Yang and Hao Wang
The linearity of conductance modulation of the artificial synapse severely restricts the recognition accuracy and the convergence rate in the learning of artificial neural networks. In this work, by alloy electrode engineering, a Ti–Ag device gained the forming-free property because Ag ions were promoted to migrate into the GeTeOx layer to form a thicker conductive filament. This facilitated a uniform
-
Structural modulation of bilayer graphene under an external electric field and carrier doping Appl. Phys. Express (IF 2.3) Pub Date : 2024-03-15 Nadia Sultana, Yanlin Gao, Mina Maruyama and Susumu Okada
Density functional theory was used to investigate the geometric structure of bilayer graphene under an external electric field with carrier doping. Our calculations revealed the crucial impact of external electric fields and the hole injection on determining the geometric structure of bilayer graphene. The bond length of graphene monotonically increased when increasing the hole doping concentration
-
Evaluation of polar alignment structure and surface anchoring energy in ferroelectric nematic liquid crystals by renormalized transmission spectroscopic ellipsometry Appl. Phys. Express (IF 2.3) Pub Date : 2024-03-14 Sakunosuke Abe, Amon Nakagawa, Yosei Shibata, Munehiro Kimura and Tadashi Akahane
It is essential to estimate the surface polar anchoring energy in order to discuss the interfacial orientation of ferroelectric nematic liquid crystals. In this study, we accurately estimated the twist angle of a -twist cell with an antiparallel rubbing manner, by means of renormalized transmission spectroscopic ellipsometry, which has a great deal of experience in measuring the twist angle of ordinary
-
A simple reflective metalens based on reverse design for an ultra-high-efficiency free space wavelength splitter Appl. Phys. Express (IF 2.3) Pub Date : 2024-03-12 Chao Wang, Yunpeng Hao, Boqi Wu, Fan Yang, Chunlei Zhao, Yaodan Chi and Xiaotian Yang
We propose two kinds of high-efficiency free-space wave splitters in the mid-IR band using reverse design. The wavelength divider based on the abnormal reflection principle realizes a beam-splitting angle of 22.00° and 10.92° by controlling the phase distribution, and the reflection efficiency of both wavelengths exceeds 50%. The wavelength divider designed based on the concept of metalens simultaneously
-
Multibeam X-ray tomography optical system for narrow-energy-bandwidth synchrotron radiation Appl. Phys. Express (IF 2.3) Pub Date : 2024-03-11 Wolfgang Voegeli, Haruki Takayama, Xiaoyu Liang, Tetsuroh Shirasawa, Etsuo Arakawa, Hiroyuki Kudo and Wataru Yashiro
The design and evaluation experiments of a multibeam X-ray tomography optical system that can be used with synchrotron radiation from sources with a narrow energy bandwidth, i.e. undulator sources, are reported. It consists of silicon single crystals that diffract the incident X-rays to 27 beams, which are used to image a sample. The energy of the beams was aligned with an accuracy sufficient for use
-
8.7 A/700 V β-Ga2O3 Schottky barrier diode demonstrated by oxygen annealing combined with self-aligned mesa termination Appl. Phys. Express (IF 2.3) Pub Date : 2024-03-11 Feihong Wu, Zhao Han, Jinyang Liu, Yuangang Wang, Weibing Hao, Xuanze Zhou, Guangwei Xu, Yuanjie Lv, Zhihong Feng and Shibing Long
β-Ga2O3 Schottky barrier diodes (SBDs) with low-defect epitaxial surface and effective termination are essential for realizing excellent blocking characteristics. This work systematically studied oxygen annealing at various temperatures, optimizing the epitaxial surface by reducing the surface roughness and dislocation density. Combined with mesa termination, the results showed that the breakdown voltage
-
Electrical properties and band alignments of Sb2Te3/Si heterojunctions, low-barrier Sb2Te3/n-Si and high-barrier Sb2Te3/p-Si junctions Appl. Phys. Express (IF 2.3) Pub Date : 2024-03-08 Naoya Okada, Wen Hsin Chang, Shogo Hatayama, Yuta Saito and Toshifumi Irisawa
We investigated the electrical junction properties of the layered Sb2Te3 film formed on Si substrates. The current−voltage characteristics of the Sb2Te3/n-Si heterojunction showed an ohmic properties, whereas the Sb2Te3/p-Si heterojunction exhibited rectifying properties with a high barrier height of 0.77 eV. The capacitance−voltage characteristics of MOS capacitors with the Sb2Te3 electrode indicated
-
Improvement of film quality and solar cell properties of perovskite by the addition of N-benzylhydroxylamine Appl. Phys. Express (IF 2.3) Pub Date : 2024-03-07 Keisuke Nagasawa, Takeshi Sano, Viet Nguyen Chau, Yutaka Okuyama, Yuya Sayama, Ryosuke Oikawa, Keigo Hoshi, Takayuki Chiba and Junji Kido
In this study on perovskite solar cells (PVSCs), we incorporate N-benzylhydroxylamine (N-BzHoA) as an additive into the precursor solution. The addition of N-BzHoA suppressed the formation of unwanted PbI2 and δ-phase perovskite without affecting the band gap, confirming uniform and large grains in the perovskite film. The fabricated inverted PVSCs exhibited remarkably improved properties compared
-
Nanosecond recombination lifetimes and spin relaxation times in (110) InGaAs/AlGaAs quantum wells at room temperature Appl. Phys. Express (IF 2.3) Pub Date : 2024-03-06 Satoshi Iba and Yuzo Ohno
Quantum wells in InGaAs/AlGaAs with (110) orientation are attractive as active layers in spin-controlled lasers with circularly polarized emission, while the spin relaxation time is expected to be larger than for (100)-oriented layers. However, the hitherto reported recombination lifetimes (40 ps) and spin relaxation times (440 ps) of (110) InGaAs/AlGaAs structures are insufficient. Here it is shown
-
Lightweight and high-precision materials property prediction using pre-trained Graph Neural Networks and its application to a small dataset Appl. Phys. Express (IF 2.3) Pub Date : 2024-03-06 Kento Nishio, Kiyou Shibata and Teruyasu Mizoguchi
Large data sets are essential for building deep learning models. However, generating large datasets with higher theoretical levels and larger computational models remains difficult due to the high cost of first-principles calculation. Here, we propose a lightweight and highly accurate machine learning approach using pre-trained Graph Neural Networks (GNNs) for industrially important but difficult to
-
Multi-focus manipulation system based on separable natural evolution strategy aberration self-calibration Appl. Phys. Express (IF 2.3) Pub Date : 2024-03-06 Linxian Liu, Jiahao Liu, Chunxu Ding, Jiamiao Yang, Jia Gao, Yuan Qu, Qiaozhi He and Rongjun Shao
Wavefront shaping using digital micromirror devices (DMDs) allows inertia-free focus manipulation with numerous modulation modes and high refresh rates. However, the aberration caused by the curvature of DMDs affects the focusing performance. Here, we propose an aberration self-calibration method based on separable natural evolution strategies. This method searches optimal Zernike coefficients of aberration
-
A two-stage insulation method for suppressing thermal crosstalk in microarray sensitive units Appl. Phys. Express (IF 2.3) Pub Date : 2024-03-06 Shining Zhu, Xin Li, Zhengjie Luo, Xuguang Jia, Yue Qin, Hao Guo, Jun Tang, Zhonghao Li, Huanfei Wen, Zongmin Ma and Jun Liu
Thermal crosstalk between array structures is a key factor in limiting the sensitivity of micro-nano array sensors. We propose a two-stage thermally isolated structure with thermal holes and heat dissipation layer and pulsed voltage heating to reduce thermal crosstalk. Through finite element thermal simulation analysis as well as thermal interference test, the results show that the thermal crosstalk
-
Extraction of interfacial thermal resistance across an organic/semiconductor interface using optical-interference contactless thermometry Appl. Phys. Express (IF 2.3) Pub Date : 2024-03-06 Jiawen Yu, Hiroaki Hanafusa and Seiichiro Higashi
We have developed an experimental method to extract interfacial thermal resistance (ITR) at an organic/semiconductor interface based on optical-interference contactless thermometry. The proposed technique was applied to a SU-8/SiC bilayer sample, and clear oscillations in reflectivity induced by optical interference during pulse heating and cooling were observed. After fitting the observed reflectivity
-
Realization of low specific-contact-resistance on N-polar GaN surfaces using heavily-Ge-doped n-type GaN films deposited by low-temperature reactive sputtering technique Appl. Phys. Express (IF 2.3) Pub Date : 2024-03-04 Shinji Yamada, Masanori Shirai, Hiroki Kobayashi, Manabu Arai, Tetsu Kachi and Jun Suda
We developed a low-temperature ohmic contact formation process for N-polar GaN surfaces. Specific-contact-resistances of 9.4 × 10−5 and 2.0 × 10−5 Ω cm2 were obtained using Ti/Al metal stacks on heavily-germanium-doped GaN films, which were deposited at 500 °C and 600 °C using a radical-assisted reactive sputtering method, respectively. The electrode sintering temperature was as low as 475 °C. Carrier
-
Magnetic field tuning of photoelectric and photoluminescence effects in BiFe0.9Co0.1O3 thin film Appl. Phys. Express (IF 2.3) Pub Date : 2024-03-04 Guanzhong Huo, Jinyan Li, Chao Su, Hongyu Xu, Guilin Chen and Shuiyuan Chen
The reported BiFe0.9Co0.1O3 film presents an interesting magnetic field tunning effect on the photoelectric properties and photoluminescence spectra. The change rate of the photocurrent up to 123.6% was achieved when applying a 400 Oe magnetic field to the film, which is attributed to the spin scattering of photoelectrons in the film. The experimental result of the magnetic field tuning photoluminescence
-
Inverted input method for computing performance enhancement of the ion-gating reservoir Appl. Phys. Express (IF 2.3) Pub Date : 2024-02-27 Yu Yamaguchi, Daiki Nishioka, Wataru Namiki, Takashi Tsuchiya, Masataka Imura, Yasuo Koide, Tohru Higuchi, Kazuya Terabe
Physical reservoir computing (PRC) is useful for edge computing, although the challenge is to improve computational performance. In this study, we developed an inverted input method, the inverted input is additionally applied to a physical reservoir together with the original input, to improve the performance of the ion-gating reservoir. The error in the second-order nonlinear equation task was 7.3
-
Tesla-class single-cycle terahertz magnetic field pulses generated with a spiral-shaped metal microstructure Appl. Phys. Express (IF 2.3) Pub Date : 2024-02-26 Kei Maruyama, Zhenya Zhang, Miharu Takumi, Takuya Satoh, Makoto Nakajima, Yoshihiko Kanemitsu, Hideki Hirori
We study the terahertz (THz) magnetic field pulse enhanced by a spiral-shaped antenna resonator (SAR). We deposit the SAR on the surface of a terbium-gallium-garnet crystal, which has a large Verdet constant, and measure the Faraday rotation angle for strong THz pulse excitation by magneto-optical sampling (MOS) with NIR light. The determined magnetic field strength and field-enhancement spectrum are
-
A time-delayed physical reservoir with various time constants Appl. Phys. Express (IF 2.3) Pub Date : 2024-02-23 Yutaro Yamazaki, Kentaro Kinoshita
Physical reservoir computing has been attracting attention in recent years. However, it remains unclear how much nonlinearity is required in the physical dynamics to achieve a high computational performance. Therefore, we focused on a resistor–capacitor circuit, which exhibits simple transient characteristics, and investigated the performance required for a physical reservoir. As a result, the proposed
-
Development of nanostructured Ge/C anodes with a multistacking layer fabricated via Ar high-pressure sputtering for high-capacity Li+-ion batteries Appl. Phys. Express (IF 2.3) Pub Date : 2024-02-23 Tomoki Omae, Teruya Yamada, Daiki Fujikake, Takahiro Kozawa, Giichiro Uchida
To realize high-capacity Ge anodes for next-generation Li+-ion batteries, a multilayer anode with a C(top)/Ge(middle)/C(bottom) structure was developed, where nanostructured amorphous Ge (a-Ge) and amorphous-like carbon films with a grain size of 10–20 nm were deposited sequentially by high-pressure Ar sputtering at 500 mTorr. Compared with the a-Ge anode, the C(top)/a-Ge(middle)/C(bottom) multistacking
-
Flexible light-induced self-written optical waveguide with 50 μm core size Appl. Phys. Express (IF 2.3) Pub Date : 2024-02-21 Ryo Futawatari, Hidetaka Terasawa, Okihiro Sugihara
We demonstrate a NIR light-induced self-written (LISW) optical waveguide between graded-index (GI) glass optical fibers with a 50 μm core size (50GIFs) using gel material. We describe the optical properties of the LISW optical solder in terms of its flexibility, adhesiveness, and loss. The results demonstrate that the two 50GIFs were self-coupled through the LISW optical waveguide, and the connection
-
Epitaxial ZnO piezoelectric layer on SiO2/Mo solidly mounted resonator fabricated using epitaxial Au sacrificial layer Appl. Phys. Express (IF 2.3) Pub Date : 2024-02-21 Satoshi Tokai, Takahiko Yanagitani
In solidly mounted resonator (SMR) type of bulk acoustic wave resonator, it is difficult to fabricate single crystalline piezoelectric thin films in a bottom-up process due to the amorphous SiO2 in the low acoustic impedance layer of the acoustic Bragg reflector. In this study, single crystalline ZnO piezoelectric layer on amorphous SiO2/polycrystalline Mo acoustic Bragg reflector is fabricated using
-
Temperature dependence of liquid-gallium ordering on the surface of epitaxially grown GaN Appl. Phys. Express (IF 2.3) Pub Date : 2024-02-20 Takuo Sasaki, Takuya Iwata, Kanya Sugitani, Takahiro Kawamura, Toru Akiyama, Masamitu Takahasi
The three-dimensional ordering of the gallium (Ga) adlayers on GaN(0001) and (000 1¯ ) surfaces was probed using in situ X-ray scattering under MBE conditions. An ordered bilayer of Ga forms on GaN(0001) but the ordering decreases at substrate temperatures of <450 °C, consistent with the mechanism of non-equilibrium epitaxial growth. Monolayer Ga that forms on GaN(000 1¯ ) is laterally disordered and
-
Demonstration of recycling process for GaN substrates using laser slicing technique towards cost reduction of GaN vertical power MOSFETs Appl. Phys. Express (IF 2.3) Pub Date : 2024-02-20 Takashi Ishida, Takashi Ushijima, Shosuke Nakabayashi, Kozo Kato, Takayuki Koyama, Yoshitaka Nagasato, Junji Ohara, Shinichi Hoshi, Masatake Nagaya, Kazukuni Hara, Takashi Kanemura, Masato Taki, Toshiki Yui, Keisuke Hara, Daisuke Kawaguchi, Koji Kuno, Tetsuya Osajima, Jun Kojima, Tsutomu Uesugi, Atsushi Tanaka, Chiaki Sasaoka, Shoichi Onda, Jun Suda
To address the issue of the high cost of GaN substrates, a recycling process for GaN substrates using a laser slicing technique was investigated. The channel properties of lateral MOSFETs and the reverse characteristics of vertical PN diodes, which represent the main components of vertical power devices, exhibited no degradation either before and after laser slicing or due to the overall GaN substrate
-
Suppression of electromagnetic crosstalk by differential excitation for SAW generation Appl. Phys. Express (IF 2.3) Pub Date : 2024-02-15 Shunsuke Ota, Yuma Okazaki, Shuji Nakamura, Takehiko Oe, Hermann Sellier, Christopher Bäuerle, Nobu-Hisa Kaneko, Tetsuo Kodera, Shintaro Takada
Surface acoustic waves (SAWs) hold a vast potential in various fields such as spintronics, quantum acoustics, and electron-quantum optics, but an electromagnetic wave emanating from SAW generation circuits has often been a major hurdle. Here, we investigate a differential excitation method of interdigital transducers to generate SAWs while reducing the electromagnetic wave. The results show that electromagnetic
-
Single-photon level ultrafast time-resolved measurement using two-color dual-comb-based asynchronous linear optical sampling Appl. Phys. Express (IF 2.3) Pub Date : 2024-02-14 Prasad Koviri, Hajime Komori, Haochen Tian, Masahiro Ishizeki, Takashi Kato, Akifumi Asahara, Ryosuke Shimizu, Thomas R. Schibli, Kaoru Minoshima
We demonstrated an ultrafast time-resolved measurement method operating at the single-photon level and employing a two-color comb-based asynchronous optical sampling (ASOPS) setup. We harnessed the two-color ASOPS photon counting approach to achieve long-term averaging of the ultralow intensity signal with a synchronized optical trigger signal, which minimizes residual timing jitter between the two
-
Synthetic method of pure-red emissive CsPbI3 under ambient conditions for quantum-dot light-emitting diode application Appl. Phys. Express (IF 2.3) Pub Date : 2024-02-07 Kenshin Yoshida, Naoaki Oshita, Taisei Kimura, Mao Goto, Ryosuke Oikawa, Mizuho Uwano, Satoshi Asakura, Takayuki Chiba, Akito Masuhara
Perovskite quantum dots (PeQDs) are expected to be used in ultra-high-definition television (UHDTV) due to their excellent optical properties. However, pure-red emissive (λ EL: 620–650 nm) PeQD-based LEDs (PeLEDs) are required for UHDTV with single-halogen PeQDs synthesized under ambient conditions, which is important for practical use. Hence, we established a novel synthetic method to prepare PeQDs
-
Voltage-controlled magnetic anisotropy effect through a high-k MgO/ZrO2/MgO hybrid tunneling barrier Appl. Phys. Express (IF 2.3) Pub Date : 2024-02-02 Hiroshige Onoda, Tomohiro Nozaki, Takayuki Nozaki, Shinji Yuasa
We investigated the voltage-controlled magnetic anisotropy (VCMA) effect in epitaxial magnetic tunnel junctions (MTJs) with a hybrid MgO/ZrO2/MgO tunnel barrier. A metastable cubic ZrO2(001) thin film was successfully grown on a MgO(001) layer, leading to the high dielectric constant of 26.5. Using the hybrid tunneling barrier, we achieved the large VCMA coefficient of −350 fJ V−1 m−1, which is 70%
-
Higher-order resonance of single-crystal diamond cantilever sensors toward high f‧Q products Appl. Phys. Express (IF 2.3) Pub Date : 2024-02-02 Guo Chen, Zilong Zhang, Keyun Gu, Liwen Sang, Satoshi Koizumi, Masaya Toda, Haitao Ye, Yasuo Koide, Zhaohui Huang, Meiyong Liao
MEMS resonant sensing devices require both HF (f) and low dissipation or high quality factor (Q) to ensure high sensitivity and high speed. In this study, we investigate the resonance properties and energy loss in the first three resonance modes, resulting in a significant increase in f‧Q product at higher orders. The third order resonance exhibits an approximately 15-fold increase in f‧Q product,
-
Realization of nociceptive receptors based on Mott memristors Appl. Phys. Express (IF 2.3) Pub Date : 2024-02-01 Yanji Wang, Yu Wang, Yanzhong Zhang, Xinpeng Wang, Hao Zhang, Rongqing Xu, Yi Tong
Nociceptive receptors are primarily responsible for detecting and responding to potentially harmful stimuli, including painful sensations and tissue damage. In this letter, we designed Pt/Ag/NbO x /W memristors with threshold switching (TS) characteristics and low working voltage attributed to the diffusion of Ag ions within the device. Furthermore, this device successfully emulates the functions of
-
Analysis and measurement of high frequency piezoelectric ring resonator Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-30 Tingting Yang, Yao Cai, Chao Gao, Qinwen Xu, Yang Zou, Yan Liu, Wenjuan Liu, Cheng Lei, Chengliang Sun
This paper introduces a piezoelectric ring resonator, comprising a Mo-ScAlN-Mo sandwich structure and shaped into a ring with a hollow center. The vibrational modes of the resonator are elucidated through simulation and theoretical analysis, and the impact of diverse geometric parameters on the resonant frequency is explored. A HF resonator with a resonance frequency of 4.168 GHz has been fabricated
-
Core–shell yarn-structured triboelectric nanogenerator for harvesting both waterdrop and biomechanics energies Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-29 Haitao Wang, Yasuyoshi Kurokawa, Jia-Han Zhang, Kazuhiro Gotoh, Xin Liu, Satoru Miyamoto, Noritaka Usami
Wearable energy harvesters (WEHs) have garnered significant attention recently due to their promising capabilities in powering wearable devices. In this research, we present a core–shell yarn-structured triboelectric nanogenerator (CY-TENG) that operates in two modes: the single-electrode TENG (SE-TENG) and the droplet-based electricity generator. This design facilitates energy harvesting from both
-
Printed organic transistors and complementary ring oscillators operatable at 200 mV Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-24 Masaya Yamada, Yasunori Takeda, Shizuo Tokito, Hiroyuki Matsui
Applications of organic thin-film transistors (OTFTs) include wearable health monitors and next-generation Internet-of-Things systems driven by a small energy-harvesting power supply. Such applications require low voltage and low power consumption organic ICs. In this paper, we demonstrate complementary ICs based on printed p-type and n-type OTFTs operatable at an ultralow supply voltage of 200 mV
-
Cathodoluminescence spectral and lifetime mapping of Cs4PbBr6: fast lifetime and its scintillator application Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-24 Tetsuya Kubota, Sotatsu Yanagimoto, Hikaru Saito, Keiichirou Akiba, Ayumi Ishii, Takumi Sannomiya
Highly efficient green emission of Cs4PbBr6 has been attributed to intermediate states formed by embedded CsPbBr3 nanocrystals or defects. However, direct experimental confirmation of the presence of such nano-emitters is not straightforward and the emission mechanism remains elusive. By using cathodoluminescence (CL) imaging with a high spatial resolution, we demonstrate that CsPbBr3 nanocrystals
-
The optical gain variation of Ge nanowires induced by L-valley splitting under the [110] direction stress Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-24 Xin Li, Ning Hou, Wen Xiong
The electronic structures of Ge nanowires under the [110] direction stress are calculated via effective-mass k·p theory, and the results manifest eight equivalent L-valleys will be split into fourfold degenerate L 1-valleys and L 2-valleys. With increasing stress, the electron levels at the L 1-valleys and L 2-valleys can be pushed close to and away from those at the Γ-valley, respectively, which causes
-
Density functional theory study on the effect of NO annealing for SiC(0001) surface with atomic-scale steps Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-19 Mitsuharu Uemoto, Nahoto Funaki, Kazuma Yokota, Takuji Hosoi, Tomoya Ono
The effect of NO annealing on the electronic structures of the 4H-SiC(0001)/SiO2 interface with atomic-scale steps is investigated. The characteristic behavior of conduction band edge (CBE) states is strongly affected by the atomic configurations in the SiO2 and the step structure, resulting in the discontinuity of the CBE states at the step edges, which prevents electrons from penetrating from the
-
Scattering-free Ce:LYBO single crystals for thermal neutron detection Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-17 Dongsheng Yuan, Encarnación G. Víllora, Daisuke Nakauchi, Takumi Kato, Noriaki Kawaguchi, Takayuki Yanagida, Kiyoshi Shimamura
Ce:Li6Y(BO3)3 (LYBO) is a well-known candidate for thermal neutron detection with a very high Li concentration (3.06 × 1022/cm3). So far, as-grown crystals exhibit a milky appearance that compromises their performance as scintillators. Current work demonstrates, for the first time, the growth of scattering-free undoped and Ce-doped LYBO by a thermal quenching process. The origin and features of the
-
Hollow Mie resonators based on toroidal magnetic dipole mode with enhanced sensitivity in refractometric sensing Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-17 Rongyang Xu, Junichi Takahara
We propose a refractometric sensor based on hollow silicon Mie resonators of a toroidal magnetic dipole mode. This mode has a pair of antiparallel electric dipoles perpendicular to the silica substrate; thus, the radiation of the mode is suppressed, resulting in an ultra-narrow reflection peak linewidth of 0.35 nm. In addition, the hollow structure enhances the interaction between the enhanced electric
-
Phononic band calculations and experimental imaging of topological boundary modes in a hexagonal flexural wave machine Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-16 Hayato Takeda, Ryoya Minami, Osamu Matsuda, Oliver B. Wright, Motonobu Tomoda
We construct a two-dimensional mechanical wave machine based on a hexagonal lattice to investigate low-frequency flexural plate waves whose propagation mimicks a topological quantum valley Hall system. We thereby demonstrate “mechanical graphene” by extension of the one-dimensional Shive wave machine to two dimensions. Imaging experiments, backed up by simulations, reveal the presence of boundary modes
-
Time-resolved force microscopy using the delay-time modulation method Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-09 Hiroyuki Mogi, Rin Wakabayashi, Shoji Yoshida, Yusuke Arashida, Atsushi Taninaka, Katsuya Iwaya, Takeshi Miura, Osamu Takeuchi, Hidemi Shigekawa
We developed a time-resolved force microscopy technique by integrating atomic force microscopy using a tuning-fork-type cantilever with the delay time modulation method for optical pump-probe light. We successfully measured the dynamics of surface recombination and diffusion of photoexcited carriers in bulk WSe2, which is challenging owing to the effect of the tunneling current in time-resolved scanning
-
High-pressure plasma etching up to 9 atm toward uniform processing inside narrow grooves of high-precision X-ray crystal optics Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-08 Shotaro Matsumura, Iori Ogasahara, Masafumi Miyake, Taito Osaka, Daisetsu Toh, Jumpei Yamada, Makina Yabashi, Kazuto Yamauchi, Yasuhisa Sano
We developed a new etching technique using plasma generated at high pressure up to 9 atm. Operating at 9-atm pressure with a 30-μm-diameter wire electrode, we demonstrated the generation of well-ordered plasma at a narrow gap of ∼10 μm between the electrode and workpiece, and realized a high spatial resolution of <40 μm during processing. This technique should allow for the processing of high-precision
-
On the mechanisms of J c increment and degradation in high-J c Ba122 tapes made by different processing methods Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-08 F. Kametani, Y. Su, C. Tarantini, E. Hellstrom, A. Matsumoto, H. Kumakura, K. Togano, H. Huang, Y. Ma
We compared the grain and grain boundary (GB) nanostructures in two Ba122 tapes with similarly high J c. The Ag-sheathed tape made by hot pressing has larger, more plate-like grains with better c-axis alignment but has more GBs blocked by FeAs and Ba–O. In contrast, the tape made by cold pressing with an Ag-Sn/stainless steel sheath possesses fewer plate-like grains and weaker grain alignment but has
-
Optical and ultrasonic dual-sensitive sensor and its application in photoacoustic microscopy Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-08 Jiaye Xu, Shiqing Wu, Chao Tao, Xiaojun Liu
Multi-modality imaging is significant for biomedical applications. We propose a dual-sensitive sensor to simultaneously detect optical and ultrasonic signals. Based upon the classical piezoelectric structure, we attach a photosensitive layer made of carbon nanotubes-polydimethylsiloxane (CNTs-PDMS) composite to the surface. The photosensitive layer absorbs light and converts it into ultrasound, while
-
Pulsed sputtering selective epitaxial formation of highly degenerate n-type GaN ohmic contacts for GaN HEMT applications Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-03 Ryota Maeda, Kohei Ueno and Hiroshi Fujioka
This study describes the selective formation process of highly degenerate n-type GaN (d-GaN) ohmic contacts for the source and drain regions of GaN high electron mobility transistors (HEMTs) using pulsed sputtering deposition (PSD). The selective formation process using SiO2 masks and PSD epitaxial growth enabled the uniform formation of d-GaN in micron-meter size. The optimally formed d-GaN exhibited
-
Green-wavelength GaN-based photonic-crystal surface-emitting lasers Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-03 Natsuo Taguchi, Akinori Iwai, Masahiro Noguchi, Hiroaki Takahashi, Atsuo Michiue, Menaka De Zoysa, Takuya Inoue, Kenji Ishizaki, Susumu Noda
Visible-wavelength GaN-based photonic-crystal surface-emitting lasers (PCSELs) have attracted attention for various applications, such as materials processing, high-brightness illuminations, and displays. In this letter, we demonstrate GaN-based PCSELs at green wavelengths. We formed a photonic crystal (PC) in p-GaN and filled holes of the PC with SiO2 to ensure device stability. Through a current
-
Rutile-type Ge x Sn1−x O2 alloy layers lattice-matched to TiO2 substrates for device applications Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-03 Hitoshi Takane, Takayoshi Oshima, Takayuki Harada, Kentaro Kaneko, Katsuhisa Tanaka
We report the characterization and application of mist-CVD-grown rutile-structured Ge x Sn1−x O2 (x = ∼0.53) films lattice-matched to isostructural TiO2(001) substrates. The grown surface was flat throughout the growth owing to the lattice-matching epitaxy. Additionally, the film was single-crystalline without misoriented domains and TEM-detectable threading dislocations due to the coherent heterointerface
-
High-voltage AlN Schottky barrier diodes on bulk AlN substrates by MOCVD Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-03 Dinusha Herath Mudiyanselage, Dawei Wang, Bingcheng Da, Ziyi He, Houqiang Fu
This letter reports the demonstration of Aluminum nitride (AIN) Schottky barrier diodes on bulk AlN substrates by metalorganic chemical vapor phase deposition with breakdown voltages exceeding 3 kV. The devices exhibited good rectifying characteristics with ON/OFF ratios of 106–108 and excellent thermal stability from 298 to 623 K. The device Schottky barrier height increased from 0.89 to 1.85 eV,
-
Identification and thermal healing of focused ion beam-induced defects in GaN using off-axis electron holography Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-03 K. Ji, M. Schnedler, Q. Lan, F. Zheng, Y. Wang, Y. Lu, H. Eisele, J.-F. Carlin, R. Butté, N. Grandjean, R. E. Dunin-Borkowski, Ph. Ebert
Thermal healing of focused ion beam-implanted defects in GaN is investigated by off-axis electron holography in TEM. The data reveal that healing starts at temperatures as low as about 250 °C. The healing processes result in an irreversible transition from defect-induced Fermi level pinning near the VB toward a midgap pinning induced by the crystalline-amorphous transition interface. Based on the measured
-
Nitrogen-displacement-related recombination centers generated by electron beam irradiation in n-type and p-type homoepitaxial GaN layers Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-03 Meguru Endo, Masahiro Horita, Jun Suda
Recombination centers originating from point defects generated by the displacement of N atoms in n-type and p-type GaN were investigated by analyzing Shockley–Read–Hall (SRH) recombination currents in homoepitaxial GaN p–n junctions. These defects were intentionally generated by electron beam (EB) irradiation at 137 keV. The net doping concentrations in p+–n junction diodes were not changed following
-
Numerical investigation of plasmon-enhanced emission from a nanofiber coupled single photon emitter Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-02 Yining Xuan, Rui Sun, Soyoung Baek, Mark Sadgrove, Keiichi Edamatsu
This study explores the enhancement of emission from a single photon emitter in a quantum communication network by coupling the source with an optical nanofiber and leveraging gold nanoparticles for Purcell enhancement. Large Purcell enhancements of more than 50 times were recently reported experimentally, but the understanding of important issues, including the maximum Purcell factor and limits to
-
Temperature-dependent Raman-active phonon modes and electron−phonon coupling in β-Ga2O3 microwire Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-02 Rongcheng Yao, Lingyu Wan, Bingsheng Li, Yuefei Wang
The lattice vibration and electron-phonon coupling (EPC) in β-Ga2O3 microwire are systematically investigated. The β-Ga2O3 microwire that is (020)-oriented shows 14 Raman peaks, with all their FWHM narrower than those of (100)-oriented β-Ga2O3 bulk single crystal. As the temperature increases from 80 to 300 K, most Raman-active phonon modes are blueshifted, while a few modes are first blueshifted and
-
Hetero-assembly design of 2D oxide nanosheets for tailored thermal shielding materials Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-02 Hirofumi Tsunematsu, Keita Nishibashi, Eisuke Yamamoto, Makoto Kobayashi, Tomohiro Yoshida, Minoru Osada
We present a new approach for designing thermal shielding materials using two-dimensional oxide nanosheets. Our approach uses hetero-assembly design [(Ti0.87O2) m (Cs2.7W11O35−d )20 (m = 0, 5, 10)] by overlaying high refractive index (n) Ti0.87O2 nanosheets with transparent conducting Cs2.7W11O35−d nanosheets. Through proper design of the thickness of high-n Ti0.87O2 layers, we achieved the optimum
-
Ultralow thermal conductivity of amorphous silicon–germanium thin films for alloy and disorder scattering determined by 3ω method and nanoindentation Appl. Phys. Express (IF 2.3) Pub Date : 2024-01-02 Daiki Tanisawa, Yoshiyuki Shionozaki, Tetsuya Takizawa, Asato Yamaguchi, Hiroshi Murotani, Masayuki Takashiri
The ultralow thermal conductivity (1.3 W/(m∙K)) of amorphous silicon–germanium films for alloy and disorder scattering was investigated using the 3ω method and nanoindentation. The films exhibited the lowest phonon mean free path (MFP) of 0.5 nm compared to that of amorphous silicon (1.1 nm) and germanium (0.9 nm) films, owing to alloy scattering in the silicon–germanium films. Based on Matthiessen’s
-
High speed evanescent waveguide photodetector with a 100 GHz bandwidth Appl. Phys. Express (IF 2.3) Pub Date : 2023-12-29 Han Ye, Qin Han, Shuai Wang, Yimiao Chu, Yu Zheng, Liyan Geng
The upcoming beyond-5G and 6G ultra-high speed transmission networks have urged photonic transceivers to allow for higher bandwidth performance. In this work, an evanescent coupled high speed waveguide photodetector (PD) is fabricated and analyzed. Adopting a modified uni-traveling carrier structure, the PD exhibits a bandwidth of 100 GHz and a low dark current of 3 nA at −1.5 V. Numerical simulations
-
Wide-field imaging of the magnetization process in soft magnetic-thin film using diamond quantum sensors Appl. Phys. Express (IF 2.3) Pub Date : 2023-12-29 Ryota Kitagawa, Teruo Kohashi, Takeyuki Tsuji, Shunsuke Nagata, Aoi Nakatsuka, Honami Nitta, Yota Takamura, Shigeki Nakagawa, Takayuki Iwasaki, Mutsuko Hatano
The magnetization process of a soft magnetic CoFeB-SiO2 thin film was imaged using diamond quantum sensors with perfectly aligned nitrogen-vacancy centers along the [111] direction formed by CVD. Around the film edge, the easy and hard axes directions exhibited different responses to the external magnetic field, consistent with ones observed by magneto-optical Kerr effect microscopy. Moreover, quantum
-
Effective suppression of interface states in recessed-gate MIS-HEMTs by TMAH wet etching Appl. Phys. Express (IF 2.3) Pub Date : 2023-12-29 Yu Li, Guohao Yu, Heng Wang, Jiaan Zhou, Zheming Wang, Runxian Xing, Shaoqian Lu, An Yang, Bingliang Zhang, Yong Cai, Zhongming Zeng, Baoshun Zhang
The effect of tetramethylammonium hydroxide (TMAH) treatment prior to gate dielectric deposition on the performance of recessed-gate AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) was investigated. Through the use of TMAH wet etching, a low roughness etched surface of 0.173 nm was obtained. The capacitance–voltage characteristics of MIS heterostructures showed
-
Separate evaluation of interface and oxide hole traps in SiO2/GaN MOS structures with below- and above-gap light excitation Appl. Phys. Express (IF 2.3) Pub Date : 2023-12-29 Takuma Kobayashi, Kazuki Tomigahara, Mikito Nozaki, Takayoshi Shimura, Heiji Watanabe
Understanding the traps in metal-oxide-semiconductor (MOS) structures is crucial in the fabrication of MOS transistors with high performance and reliability. In this study, we evaluated the hole traps in SiO2/GaN MOS structures through photo-assisted capacitance-voltage measurements. Below- and above-gap light was used to distinguish between the contributions of fast interface and slow oxide hole traps
-
Structural characterization of epitaxial ScAlN films grown on GaN by low-temperature sputtering Appl. Phys. Express (IF 2.3) Pub Date : 2023-12-29 Atsushi Kobayashi, Yoshio Honda, Takuya Maeda, Tomoya Okuda, Kohei Ueno, Hiroshi Fujioka
ScAlN has garnered substantial attention for its robust piezoelectric and ferroelectric properties, holding promise for diverse electronic device applications. However, the interplay between its structural attributes and physical properties remains poorly understood. This study systematically elucidates the structural characteristics of epitaxial ScAlN films grown on GaN by low-temperature sputtering
-
Effect of interface quality on spin Hall magnetoresistance in Pt/MgFe2O4 bilayers Appl. Phys. Express (IF 2.3) Pub Date : 2023-12-27 Masafumi Sugino, Kohei Ueda, Takanori Kida, Masayuki Hagiwara and Jobu Matsuno
We report on spin Hall magnetoresistance (SMR) in bilayers composed of Pt and magnetic insulator MgFe2O4 (MFO) with spinel structure. The Pt thickness dependence of the SMR reveals that annealing of the MFO surface before depositing the Pt layer is crucial for a large SMR with better interface quality. We also found that oxygen pressure during the MFO growth hardly affects the SMR, while it influences
-
Lattice thermal conductivity of β-, α- and κ- Ga2O3: a first-principles computational study Appl. Phys. Express (IF 2.3) Pub Date : 2023-12-27 Jinfeng Yang, Yongze Xu, Xiaonan Wang, Xu Zhang, Yang He and Huarui Sun
The thermal transport properties of Ga2O3 in different phases remain inadequately explored. We employ first-principles calculations and the phonon Boltzmann equation to systematically study the lattice thermal conductivity of β-, α- and κ-Ga2O3. Our results reveal that κ-Ga2O3 exhibits pronounced phonon anharmonicity due to its complex polyhedral configurations and weak bonding, resulting in significantly