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  • Electrochemical characterization of the plasma-water interface
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-18
    Trey Oldham, Moshan Chen, Stephen Sharkey, Kimberly M Parker and Elijah Thimsen

    Nonthermal atmospheric pressure plasmas generated using noble gases act as gaseous electrodes capable of promoting electrochemical reactions when in contact with aqueous media. Despite overwhelming evidence in favor of the interfacial region between the plasma and solution being a reducing environment, the plasma-liquid interface has not been evaluated from an electrochemical perspective. Herein, we present an electrochemical method to measure the overpotential at the plasma-liquid interface of solutions containing organic redox couples. Negative overpotentials indicate that the interfacial region is a reducing environment, which is consistent with the results of colorimetric assays using redox indicators. The reaction rates are related to the magnitude of the overpotential, as expected from electrochemical kinetic models. The ability to characterize the overpotential of plasma-liquid interfaces adds to the plasma electrochemistry toolkit and contributes to efforts being made to...

    更新日期:2020-02-18
  • Numerical thermofluid simulation on tandem type of induction thermal plasmas with and without current modulation in a lower coil
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-18
    Kazuki Onda, Yasunori Tanaka, K Akashi, Y Nakano, T Ishijima, Y Uesugi, S Sueyasu, S Watanabe and K Nakamura

    This paper describes numerical calculations on tandem-type induction thermal plasmas with and without current modulation of the lower coil. The tandem type of induction thermal plasma (tandem-ITP) has been developed with two independent rf coils in one plasma torch for stable operation and spatial control of temperature field in ITP. Furthermore, the coil current modulation for tandem-ITP, i.e. tandem type of pulse-modulated induction thermal plasma (tandem-PMITP), is expected to offer a temporo-spatially varying temperature field in the plasma torch. First, as described in this paper, a numerical thermofluid model was developed for tandem-ITP/PMITP with an upper coil and a lower coil to investigate unique temperature and gas flow fields. Secondly, the influence of gap length between the upper coil and the lower coil was studied in the tandem-ITP under steady state conditions. Results show that a shorter gap length between two coils of the tandem-ITP is favourable for materials ...

    更新日期:2020-02-18
  • Double intermediate bonding layers for the fabrication of high-quality silicon-on-insulator-based exfoliated Ge film with excellent high-temperature characteristics
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-18
    Shaoying Ke, Jinrong Zhou, Ziwei Wang, Donglin Huang, Yuxiang Wang, Qiang Peng, Cheng Li and Songyan Chen

    We investigate the high-temperature characteristics of wafer-bonded silicon-on-insulator (SOI)-based Ge film with two different intermediate bonding layers. For an amorphous Ge (a-Ge) bonding layer, due to the crystallization of a-Ge, many gas bubbles appear at the bonded interface to form Ge pits on the SOI. When the wafer pairs are annealed at ⩾400 °C, new gas bubbles appear and merge, leading to cracking of the Ge film due to the fact that the new gas bubbles cannot be transferred sufficiently rapidly out of the bonded interface of two single-crystal materials. For an a-Ge/a-Si bonding layer, the porous a-Si can serve as a reservoir at the bonded interface to absorb the by-products. With increase in a-Si layer thickness, the gas bubble density decreases. New gas bubbles are not observed after annealing at 500 °C when a 30 nm thick a-Si layer is introduced. More importantly, the quality of the Ge film with an a-Ge/a-Si bonding layer significantly improves after post-annealing...

    更新日期:2020-02-18
  • A dual natural lithium formate/L-alanine EPR dosimeter for a mixed radiation field in a boron neutron capture therapy irradiation facility
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-14
    G Alejandro, J Longhino, N R Álvarez, E Pawlak and A Butera

    Standard commercial L-alanine pellets and specially prepared natural lithium formate monohydrate powder samples of specific granulometry were irradiated in a 60 Co gamma-ray irradiation plant and in the mixed field (thermal neutrons and gamma photons) of a boron neutron capture therapy (BNCT) experimental facility. The γ -doses applied with the 60 Co source range from 0.1 to 50 kGy, while those in the BNCT facility go from ~7 Gy to 150 Gy. The thermal neutron fluences range from 10 12 neutrons cm −2 to 2 10 13 neutrons cm −2 . The irradiation of materials promotes the creation of stable electronic defects (generally free radicals) which constitute paramagnetic centers that can be detected and quantified by electron paramagnetic resonance (EPR). After irradiation, the EPR characterization of the samples was performed by determining the EPR intensity of the spectrum relative to a reference standard constituted by Mn<...

    更新日期:2020-02-14
  • A comparative study of Ac-dielectric barrier discharge versus Ns-dielectric barrier discharge plasma actuators in an incompressible turbulent mixing layer
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-14
    Ashish Singh and Jesse Little

    A comparison between ac-dielectric barrier discharge (DBD) and ns-DBD plasma actuators is performed in a low-speed turbulent mixing layer to assess differences in their control mechanisms (momentum versus thermal). The mean flow response to actuation is matched for the two cases at a single downstream location to gauge scaling of relevant parameters (carrier frequency, energy per pulse, etc). The similarity between local behavior downstream is found to extend to the global flow, both in the mean and fluctuating components. However, the ns-DBD requires approximately six times more electrical energy to achieve the same control as the ac-DBD in this specific flow. An analysis of the flow field very near the splitter plate trailing edge sheds light on the difference in momentum versus thermal actuation mechanisms. A velocity deficit is observed for both actuators, but a thermal bump effect is evident in the ns-DBD case while a near surface jet is observed in the ac-DBD case.

    更新日期:2020-02-14
  • Between life and death: strategies to reduce phototoxicity in super-resolution microscopy
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-14
    Kalina L Tosheva, Yue Yuan, Pedro Matos Pereira, Siân Culley and Ricardo Henriques

    Super-resolution microscopy (SRM) enables non-invasive, molecule-specific imaging of the internal structure and dynamics of cells with sub-diffraction limit spatial resolution. One of its major limitations is the requirement for high-intensity illumination, generating considerable cellular phototoxicity. This factor considerably limits the capacity for live-cell observations, particularly for extended periods of time. Here, we give an overview of new developments in hardware, software and probe chemistry aiming to reduce phototoxicity. Additionally, we discuss how the choice of biological model and sample environment impacts the capacity for live-cell observations.

    更新日期:2020-02-14
  • Factors contributing to the local polar-structural heterogeneity and ultrahigh piezoelectricity in Sm-modified Pb(Mg 1/3 Nb 2/3 )O 3 –PbTiO 3
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-14
    Naveen Kumar, Anupam Mishra, Arnab De, Uma Shankar and Rajeev Ranjan

    Recently, an ultrahigh piezoelectricity (longitudinal piezoelectric coefficient d 33 ~ 1500 pC/N) was reported in polycrystalline specimens of Sm-modified relaxor ferroelectric system Pb(Mg 1/3 Nb 2/3 )O 3 –PbTiO 3 (PMN–PT) (Li et al 2018 Nat. Mater . 17 349). Here, we examine the factors associated with this anomalous phenomenon by carrying out a comparative structural, dielectric, ferroelectric and impedance spectroscopy on Sm-free 0.71PMN-0.29PT (piezoelectric coefficient d 33 ~ 380 pC/N) and its Sm modified counterpart ( d 33 ~ 1160 pC/N). We found that, apart from inducing a Cm → P 4 mm inter-ferroelectric instability, Sm modification stabilizes a considerable degree of oxygen vacancies, with Sm exhibiting valence fluctuation. Based on our results, we argue that these defect types are the important source for creating structural-polar heterogene...

    更新日期:2020-02-14
  • Tunable crystallization mechanism of Sb 4 Te films by VO 2 nano-grid framework for breaking through the trade-off between thermal stability and crystallization speed
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-14
    Yang Li and Yegang Lu

    The thermal stability and optical bandgap of the amorphous Sb 4 Te film can be improved significantly by combining with VO 2 , which leads to a high crystallization temperature (around 220 °C), good data retention (ten-year data retention above 130 °C), and high amorphous resistance. The crystallization mechanism of Sb 4 Te changes from growth-dominated mode into nucleation-dominate one, which is confirmed by in situ microstructure observation experimentally and crystallization kinetics index theoretically, due to the long-range orders of Sb–Te and Sb–Sb bonds disorganized by the introduction of VO 2 nano-grid framework. The Sb 4 Te crystallites can be refined and confined in the VO 2 nano-grid framework. VO 2 –Sb 4 Te films with less than 15 at.% of VO 2 maintain the high crystallization speed. The nano-grid framework of VO 2 enables an efficient way to invade the long-order bon...

    更新日期:2020-02-14
  • Manipulation of self-organized nanograting for erasing and rewriting by ultrashort double-pulse sequences irradiation in fused silica
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-14
    Wencheng Zhang, Qinxiao Zhai, Juan Song, Kongyu Lou, Yuedong Li, Zhongmin Ou, Quanzhong Zhao and Ye Dai

    The formation process of self-organized nanograting in fused silica glass with femtosecond laser (1 kHz, 120 fs, 800 nm) double-pulse sequences irradiation is investigated by combined control of polarization state of individual pulse, interpulse temporal delay (from −330 to 350 ps) and energy ratio in each sequence. It is found that the as-formed nanograting induced by the first pulse can be erased by the second pulse in repeated sequences irradiation, and moreover a new one is be rewritten in situ if the two pulses in a sequence were temporally well separated. The rewritten nanograting shows a new orientation perpendicular to the polarization direction of the second pulse. Additionally, the erasing and rewriting of nanograting can become more efficient as long as the second pulse energy increases to be higher than the first one, regardless of the interpulse delay. Our result shows that the energy ratio in double-pulse sequences plays a decisive role in the erasing and r...

    更新日期:2020-02-14
  • Control of pathogenic bacteria on the surface of rolling fruits by an atmospheric pressure air dielectric barrier discharge system
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-14
    Yao Zhao, Yang Xia, Ting Xi, Di Zhu, Qiang Zhang, Zhihua Qi, Dongping Liu and Wenchun Wang

    Atmospheric pressure cold plasma technology has great application potential in the field of food safety. A novel atmospheric air dielectric barrier discharge device has been designed to generate plasma directly on the surface of spherical fruit. This device consists of the quartz tube, the high-voltage electrode attached to the outer wall of the quartz tube, and the fruit placed onto the inner surface of the quartz tube, acting as the ground electrode. The intensified charge-coupled detector images show that a uniformly scanning discharge channel is formed between the surface of treated substance and the inner wall of quartz tube. When the treated substance is rolled in the device, the uniform plasma is directly formed over the fruit surface. The bactericidal efficiency of plasma against pathogenic microorganisms on rolling fruit surface has been studied. The number of Staphylococcus aureus ( S. aureus ) on the surface of fruit treated by plasma for 15 s in rolling s...

    更新日期:2020-02-14
  • Luminescence and afterglow due to defects in β -SiAlON crystal powder
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-14
    Yoriko Suda, Yoshiaki Kamigaki, Hayato Miyagawa, Takashi Takeda, Kohsei Takahashi and Naoto Hirosaki

    Si 6− z Al z O z N 8− z ( β -SiAlON):Eu 2+ is among the most suitable green phosphors for white LEDs. To further improve the performance of this phosphor, it is important to investigate the properties of the nitride host crystal, β -SiAlON, which is considered to contain nitrogen vacancy defects (V N ) to some extent. From time-resolved fluorescence (TR-F) measurements of β -SiAlON without luminescent activators, we observed blue, yellow, and ultraviolet emissions. We focused on the blue emission typically centered at 460 nm, which was quenched at room temperature, but showed a continued afterglow for several milliseconds. The electron spin resonance signal of Si dangling bonds due to V N in β -SiAlON was observed to have a high concentration of 5.8 × 10 16 g −1 . We have previously reported the blue emission in nitride phosphor CaAlSiN

    更新日期:2020-02-14
  • Filtering microwave differential signals through odd-mode spoof surface plasmon polariton propagation
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-14
    Mingzhu Du, Yijun Feng, Ke Chen and Junming Zhao

    Recently, spoof surface plasmon polaritons (SPPs) have been successfully applied to microwave signal propagation in ultra-thin planar circuits, due to their unique features of electromagnetic (EM) wave confinement in deep subwavelength scale and controllable dispersive properties. Both even and odd modes can be supported in symmetric spoof SPP structures. However, most device applications employ even mode propagation due to its easy stimulation. In this paper we investigate the dispersion characteristics and EM field patterns of both even and odd modes in a symmetric H-shaped spoof SPP structure. We concentrate on odd modes with an anti-symmetric electric field distribution, and their application to the propagation and filtering of differential signals. With odd modes, a balanced bandpass filter (BPF) can be constructed with a designable passband depending on the dispersion engineering of the odd modes in the spoof SPP structures. Pure odd mode propagation provides an ideal plat...

    更新日期:2020-02-14
  • Flexible and transparent planar supercapacitor based on embedded metallic mesh current collector
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-13
    Ji-Peng Chen, Wenbin Huang, Zhou-Ying Jiang, Jian-Long Xu, Shi-Qing Zhao and Yan-Hua Liu

    The preparation of planar transparent flexible supercapacitors with high energy storage capacity, high mechanical properties and excellent optical properties is still a great challenge. The typical planar supercapacitor electrodes adopting the interdigital structure are semi-transparent, for the interdigital parts are opaque. Herein, we report a highly transparent and flexible planar supercapacitor by utilizing the embedded metallic mesh as the current collectors. The embedded metallic mesh with an interdigital structure, which was fabricated though the selective electrodeposition and film-invertion techniques, was employed as the planar supercapacitor electrode after being loaded with MnO 2 by electrochemical deposition. The realized planar solid-state supercapacitor exhibits high performance electrochemical characters and high transparency with an areal capacitance of 1.33 mF cm −2 and an optical transmittance of 81.7%. Further, the planar solid-state super...

    更新日期:2020-02-13
  • Observation of plasmon boosted photoelectrochemical activities on single Au/Cu 2 O nanoelectrode
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-13
    Yuanyuan Qian, Jun Liu, Bo-tao Zhang, Yanbin Huang, Dawei Cao, Kuankuan Ren, Haoran Tang, Yang Sun, Qicong Li, Cheng Yang, Shengchun Qu, Zhijie Wang and Yongxin Li

    Plasmon related photoelectrochemical (PEC) reactions have been widely reported on metallic nanostructures in a large scale. However, the detailed information on single nanostructure has been rarely reported. Herein, we construct nanoelectrode based on single Au/Cu 2 O nanowire to unveil how surface plasma in Au nanowire impact the PEC behavior of Au/Cu 2 O nanoelectrode with diameter as small as 100 nm. Even in such low dimension, we could still observe obvious photocurrent in the scale of nanoamperes. The contribution of plasma in Au nanowire has been confirmed by the external quantum yield spectra and the exponential curve of photocurrent versus light intensity. Importantly, H 2 bubble has also been observed in the water reduction process. Thus, insights on PEC reactions in nanoscale have been provided.

    更新日期:2020-02-13
  • High photon count rates improve the quality of super-resolution fluorescence fluctuation spectroscopy
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-13
    Falk Schneider, Pablo Hernandez-Varas, B Christoffer Lagerholm, Dilip Shrestha, Erdinc Sezgin, M Julia Roberti, Giulia Ossato, Frank Hecht, Christian Eggeling and Iztok Urbančič

    Probing the diffusion of molecules has become a routine measurement across the life sciences, chemistry and physics. It provides valuable insights into reaction dynamics, oligomerisation, molecular (re-)organisation or cellular heterogeneities. Fluorescence correlation spectroscopy (FCS) is one of the widely applied techniques to determine diffusion dynamics in two and three dimensions. This technique relies on the temporal autocorrelation of intensity fluctuations but recording these fluctuations has thus far been limited by the detection electronics, which could not efficiently and accurately time-tag photons at high count rates. This has until now restricted the range of measurable dye concentrations, as well as the data quality of the FCS recordings, especially in combination with super-resolution stimulated emission depletion (STED) nanoscopy. Here, we investigate the applicability and reliability of (STED-)FCS at high photon count rates (average intensities of more ...

    更新日期:2020-02-13
  • Bias stress and humidity exposure of amorphous InGaZnO thin-film transistors with atomic layer deposited Al 2 O 3 passivation using dimethylaluminum hydride at 200 °C
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-13
    Dianne C Corsino, Juan Paolo S Bermundo, Mami N Fujii, Kiyoshi Takahashi, Yasuaki Ishikawa and Yukiharu Uraoka

    Highly reliable amorphous InGaZnO ( a -IGZO) (In:Ga:Zn:O = 2:2:1:7) thin-film transistors (TFTs) were fabricated with 25 nm-thick Al 2 O 3 passivation deposited by atomic layer deposition (ALD) using dimethylaluminum hydride (DMAH). Al 2 O 3 passivation deposited at various temperatures was studied to determine its effect on TFT behavior following gate bias stress and humidity exposure. The Al 2 O 3 -passivated a -IGZO TFTs demonstrated an on-off current ratio ( I on / I off ) of ~10 8 and linear mobility ( µ ) of 9 to 13 cm 2 V −1 s −1 . An optimum ALD temperature of 200 °C was demonstrated to result in Al 2 O 3 -passivated a -IGZO TFTs with very small on-voltage shifts of 0.3 V and −2.7 V against positive bias stress and negative bias illumination stress (NBIS) after 10 000 s of stress time. Furthermore, negli...

    更新日期:2020-02-13
  • Ammonia synthesis over γ -Al 2 O 3 pellets in a packed-bed dielectric barrier discharge reactor
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-13
    Xinbo Zhu, Xueli Hu, Xiqiang Wu, Yuxiang Cai, Hongbin Zhang and Xin Tu

    In this work, ammonia (NH 3 ) synthesis from N 2 and H 2 was carried out in a packed-bed dielectric barrier discharge (DBD) reactor, while three kinds of commercial packing materials including acidic γ -Al 2 O 3 , alkaline γ -Al 2 O 3 and neutral alumina pellets were employed. The effect of packing materials on plasma-assisted NH 3 synthesis was investigated and compared with an unpacked DBD reactor. The results show that the presence of packing materials enhanced the plasma-assisted NH 3 synthesis by 15.6% to 44.4% compared to the plasma reaction without a packing. The highest NH 3 concentration of 1565.5 ppm was obtained over the alkaline γ -Al 2 O 3 packed plasma reactor. The improvement of packing materials on plasma-assisted NH 3 synthesis followed the order of alkaline γ -Al 2 O 3 > neutral γ -Al<...

    更新日期:2020-02-13
  • Research on continuous leakage location of stiffened structure based on frequency energy ratio mapping method
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-13
    Yu Zhang, Guixuan Yue, Lei Qi and Xiaobo Rui

    The stiffened structure has a complex effect on signal propagation and poses difficulties in leakage location technology. In order to solve this problem, this paper proposes a frequency energy ratio mapping method (FERMM). The method divides the grid on the structure in advance, compares the signal of the distributed sensor with the reference signal to generate a mapping matrix frome the energy ratio vector. When a leak at an unknown location occurs, the energy ratio vector is formed by the same method and matched with the mapping matrix to locate the unknown leakage. The energy ratio vector of this method are only related to the propagation path and are independent of the spectral characteristics of the leakage and the frequency response characteristics of the receiving sensor. FERMM has the adaptability to complex structures and can locate continuous signals for a fast real-time process. The FERMM was verified by 120 sets of experiments. The results show that the average posit...

    更新日期:2020-02-13
  • Modulation and mechanism of shockwaves induced on metals by femtosecond laser double-pulse
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-13
    Guoyan Wang, Jingya Sun, Pengfei Ji, Jie Hu, Jiaxin Sun, Qingsong Wang and Yongfeng Lu

    An ultrafast pump-probe shadowgraph imaging system and a laser induced breakdown spectroscopy (LIBS) system were used to investigate the modulation and mechanism of shockwaves of nickel (Ni) and aluminum (Al) induced by femtosecond laser double-pulse. With a suitable pulse delay, the bulge in the axial direction of the shockwave can be effectively eliminated and the shockwave expanded evenly in a hemispheric structure. The radial expansion distance of shockwaves of Ni and Al increased by 30% and 50% respectively with double-pulse excitation. The strong coupling of laser with liquid layer and plasma shielding effect were responsible for the enhancement of shockwaves within different regimes of pulse delay. Different enhancement trends were observed for the shockwaves of Ni and Al in the initial regime of pulse delay. Further study indicated that the reduced ablation volume of Al counteracted the enhancement effect of double-pulse on plasma and shockwave and it was the dominant me...

    更新日期:2020-02-13
  • High photocatalytic activity of 2D sheet structure ZnO/Bi 2 WO 6 Z-scheme heterojunction under simulated sunlight
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-12
    Jihai Duan, Miyu Liu, Yue Guo, Weiwen Wang, Zisheng Zhang and Chaojie Li

    The ZnO/Bi 2 WO 6 sheet structure was synthesized by a simple two-step hydrothermal method, and the structure in which the sheet was in close contact with the sheet improved the photocatalytic performance of Bi 2 WO 6 . Under simulated sunlight, ZnO/Bi 2 WO 6 showed excellent photocatalytic activity for the degradation of phenolic contaminants. The degradation rate of (1:1) ZnO/Bi 2 WO 6 to phenol, p-nitrophenol and p-chlorophenol was about 4 times, 7.69 times and 5 times than pure Bi 2 WO 6 , respectively. The increase in photocatalytic activity is attributed to the Z scheme heterostructure formed by the two semiconductors, which can effectively separate photogenerated carriers. Compared with a single catalyst, ZnO/Bi 2 WO 6 exhibits excellent charge transport properties in photoelectric conversion. Trap experiments of active species have shown that h + and ##IMG##

    更新日期:2020-02-12
  • Deterministic magnetic domain wall motion induced by pulsed anisotropy energy
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-12
    A W Rushforth, R Rowan-Robinson and J Zemen

    We propose a method to induce deterministic motion of a magnetic domain wall in a nanowire by inducing short strain pulses uniformly along the nanowire. Via inverse magnetostriction, a strain pulse causes the magnetic anisotropy to vary uniformly on a timescale comparable to the magnetisation dynamics. The resultant torque on the magnetic moments within the domain wall cause it to move along the nanowire. Using numerical calculations we analyse in detail the dependence of the domain wall’s motion on the material’s parameters and on the anisotropy pulse profile, and we consider the specific case of the anisotropy induced by voltage pulses applied to a hybrid piezoelectric/ferromagnet device. The method will be applicable to a range of magnetic textures including skyrmions, solitons, and domain walls in antiferromagnets, and is prospective for applications in a range of areas including ultra-energy efficient information storage and processing, communications technologies, position...

    更新日期:2020-02-12
  • Orientational transition of tin phthalocyanine molecules in the self-assembled monolayer
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-10
    Da-Xiao Yang, Zi-Long Wang, Ming-Xia Shi, Kai Sun, Min-Long Tao, Ji-Yong Yang and Jun-Zhong Wang

    The molecular orientations and self-assembled arrangements of organic molecules determine the properties of thin films. Here we report the orientational transitions of tin phthalocyanine (SnPc) molecules in the self-assembled structures on Cd(0 0 0 1) surfaces. In the monolayer regime, the low-temperature deposited SnPc molecules form a close-packed phase and ordered arrays of heptamers as well as an ultra-dense-packed monolayer. In particular, all molecules in the close-packed phase are flat-lying, and one seventh of the molecules in the heptamer are tilted, while all molecules in the ultra-dense-packed phase are tilted. These results demonstrate that the specific orientations of SnPc depend on the competition between intermolecular and molecule-substrate interfacial interactions.

    更新日期:2020-02-10
  • The self-repairing of ion irradiation damaged Mo–S–Ti (MoST) lubricant films by thermal annealing
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-10
    Zewen Duan, Haixia Jiang, Li Qiao, Liqiang Chai, Peng Wang, Xiaoyu Zhao and Weimin Liu

    Mo–S–Ti composite films deposited by magnetron sputtering were irradiated by 2 MeV Au 2+ with a high fluence of 3.3 × 10 15 ion cm −2 . Upon intense bombardment by 2 MeV Au 2+ , the Mo–S–Ti thin film exhibits sensitivity to radiation-induced amorphization at room temperature. Afterwards, thermal annealing experiments on the irradiated thin films were conducted over the temperature range of 200 °C–900 °C. Subsequent annealing experiments found that the effect of heavy ion irradiation on Mo–S–Ti films was a reversible reaction, with the irradiation-damaged MoS 2 lattice being completely self-repaired by thermal annealing. In the annealing temperature range of 200 °C–600 °C, no evidence of an amorphous to recrystallized transition was observed. When the temperature was increased to as high as 700 °C, the damaged MoS 2 molecules were well recrystallized. HRTEM images of irradiated samples annealed at 700 °C strikingly found...

    更新日期:2020-02-10
  • Programmable microwire composites: from functional units to material design
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-10
    A Uddin, D Estevez, F X Qin and H X Peng

    Microwire composites possess a wide range of functionalities that can be actively manipulated by magnetic field/stress stimuli or hybridization. Beyond those strategies, here we focus on programming microwave response by designing the wire functional units and assembling them in a specific arrangement. The programming was based on a code type defined by structural relaxation and electromagnetic damping and on a code pattern by wave attenuation, effective conductivity and near-field interaction effects. Structural relaxation was achieved by current annealing the wires, which was reflected in changes in Curie temperature, structural, magnetic and electrical properties. The wave propagation mapped by the transmission coefficient was manipulated by the wire concentration and periodicity and by arrangement of as-cast and annealed wires in their array. Increasing the wire concentration blueshifted the transmission band of the wire composites due to larger conductivity, while decreasin...

    更新日期:2020-02-10
  • Surface charge transport behavior and flashover mechanism on alumina/epoxy spacers coated by SiC/epoxy composites with varied SiC particle size
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-10
    Jianyi Xue, Yuan Li, Junhao Dong, Junhong Chen, Wendong Li, Junbo Deng and Guan-Jun Zhang

    Charge accumulation phenomenon on gas–solid interface greatly restricts the development of HVDC energy transmission system. In this study, the surface charge transport behavior and flashover performance on alumina/epoxy spacer coated by SiC/epoxy composites are experimentally investigated under DC stress. SiC/epoxy composites with varied SiC particle size are fabricated and deposited on spacer surface. Nearly a charge free surface is achieved especially at smaller SiC particle size, even when metallic wires are adhered on spacer surface and connected to high voltage electrode. The DC flashover voltage increases with the decrease of SiC particle size. On the one hand, smaller SiC particle size exhibits more outstanding nonlinear conductivity characteristics, contributing to accelerating charge dissipation, whereas on the other hand, it would introduce plenty of shallow traps due to the increased interfacial regions between SiC particle and epoxy matrix, resulting in aggravating c...

    更新日期:2020-02-10
  • Comparison of different electrospinning technologies for the production of arrays with multifunctional properties: fluorescence, conduction and magnetism
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-10
    Jiao Tian, Qianli Ma, Wensheng Yu, Dan Li, Xiangting Dong, Guixia Liu and Hui Yu

    In order to efficiently select a specific electrospinning technology to construct multifunctional nanomaterials according to their actual demands, herein, we utilize the same spinning dopes to construct fluorescent-conductive-magnetic trifunctional array. This is a case study to compare the advantages and disadvantages of four electrospinning technologies including conjugate electrospinning (CJE), parallel electrospinning (PE), coaxial electrospinning (CAE) and traditional electrospinning (TE) technologies, and further systematically investigate the differences in structure and properties of the electrospun products. The results indicate that CAE technology is more suitable to prepare multifunctional materials with fluorescent property, and PE technology is more beneficial for the fabrication of Janus-structured multifunctional materials with conductive anisotropy. Janus-structured materials can be constructed by PE and CJE technologies, but CJE technology is a better choice to ...

    更新日期:2020-02-10
  • Correlation between the photocatalysis and growth mechanism of SnO 2 nanocrystals
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-10
    Hongquan Zhan, Ce Deng, Xiao-Lei Shi, Chuanqi Wu, Xiaohong Li, Zhipeng Xie, Changan Wang and Zhi-Gang Chen

    Due to the special structural defects, SnO 2 -based nanomaterials show full potentials for applying to photocatalysis. In this work, we explore the relationship between photocatalysis and growth mechanism of SnO 2 nanocrystals. Through a pH-modifying method, the growth of SnO 2 nanocrystals follows Ostwald ripening (OR) mode at pH = 9, and oriented attachment (OA) mode at pH = 1.5, respectively. We comprehensively studied the structural characteristics of SnO 2 nanocrystals by investigating high-resolution transmission electron microscope, x-ray diffraction, Brunauer–Emmett–Teller nitrogen physisorption, UV–vis diffuses reflectance, and photoluminescence spectra, and the results with growth dynamic simulation show that OA mode is obviously different from OR mode, and the photocatalytic performance of SnO 2 nanocrystals varies under different growth mechanisms. The factors including crystal structure, particle size, and defects...

    更新日期:2020-02-10
  • In-package cold plasma decontamination of fresh-cut carrots: microbial and quality aspects
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-07
    Nikhil Kumar Mahnot, Lih-Peng Siyu, Zifan Wan, Kevin M Keener and N N Misra

    Cold plasma is a promising nonthermal technology for the decontamination and preservation of fresh and fresh-cut produce. The rapid action of a cocktail of reactive oxygen and nitrogen species in plasma against a variety of food spoilage and pathogenic organisms make it a suitable decontamination intervention. This study evaluates the effectiveness of high voltage atmospheric cold plasma in reducing the natural microflora of carrots treated at 60, 80, and 100 kV (60 Hz frequency) for 1, 2, 3, 4, and 5 min. About 2 log 10 CFU/g reduction in the population of both, total aerobic mesophiles, and yeast and mold was observed in carrot discs treated at 100 kV for 5 min (~250 W power). The changes in pH, colour, texture, and total carotenoids of cold plasma treated carrots were minor. For shelf-life evaluation of plasma treated cut-carrots voltages between 80 to 100 kV and treatment times between 4 to 5 min is recommended, such that reduction in spoilage microflora and qualit...

    更新日期:2020-02-07
  • Tunable strontium titanate terahertz all-dielectric metamaterials
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-07
    Xiaoyong He, Fangting Lin, Feng Liu and Wangzhou Shi

    Based on SrTiO 3 (STO) elliptical metamaterials (MMs) structures, the tunable propagation properties have been systematically investigated in the THz regime, including the effects of temperatures, incident angles, operation frequencies, and graphene Fermi levels. The results reveal that STO MMs manifest excellent thermally tunable properties, e.g. the amplitude and frequencies modulation depths are larger than 95.3% and 21.8% if temperature varies in the range of 70–320 K. The incident angles affect the resonant curves significantly, the amplitude modulation depth approximates 90% by changing the polarization angles, and the Q -factor reaches more than 20. The tunable Fano resonances can be achieved by utilizing a symmetrical STO-graphene structure. If the graphene Fermi level changes in the range of 0.3–1.0 eV, the amplitude modulation depth of transmission curve is more than 80%. The results are very helpful to understand the resonant mechanisms of ferroelectri...

    更新日期:2020-02-07
  • Topotactic transition between perovskite and brownmillerite phases for epitaxial LaCoO 3− δ films and effects thus resulted
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-07
    Hailin Huang, Jine Zhang, Hui Zhang, Furong Han, Xiaobing Chen, Jinghua Song, Jing Zhang, Shaojin Qi, Yuansha Chen, Jianwang Cai, Fengxia Hu, Baogen Shen and Jirong Sun

    Oxygen vacancy distribution has a direct effect on the crystal structure and physical properties of complex oxides, resulting in versatile applications. Here, we report on a reversible topotactic phase transition between the perovskite and brownmillerite structures for the LaCoO 3− δ ( δ = 0–0.5) epitaxial film by annealing the sample under different conditions. In the atmosphere of 2 × 10 −4 Pa, LaCoO 3 film is transformed from the perovskite structure to the brownmillerite structure when annealing temperature exceeds 500 °C. Meanwhile, the magnetic order transits from ferromagnetic to anti-ferromagnetic. Variable-range hopping demonstrates the electronic transport process for both phases. The incorporation of oxygen vacancies results in an upward shift of the ln ρ - T −1/4 curve, without affecting the ln ρ - T −1/4 slope. We found signatures for preferential distribution for oxygen vacan...

    更新日期:2020-02-07
  • Exchange bias and anomalous Hall effect in a wide temperature range of 5–300 K in non-collinear antiferromagnetic Mn–Cr–Sn alloy
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-07
    Z H Liu, K K Chang, Q Q Zhang, Y J Zhang and X Q Ma

    In this paper, noncollinear antiferromagnets Mn3.1Sn0.9 and Mn2.5Cr0.6Sn0.9 with an Ni3Sn-type hexagonal structure has been synthesized. An exchange bias (EB) from 5 K to room temperature has been observed in Mn 2.5 Cr 0.6 Sn 0.9 with a maximum EB field of 3166 Oe at 5 K, which decreases gradually to 60 Oe at 300 K. It is proposed that the EB is ascribed to the exchange anisotropy between the ferromagnetic component and the antiferromagnetic host due to the magnetic inhomogeneity of the materials. Large anomalous Hall effect ranging from 3.5 to 1 µ Ω · cm persists from 5 K to 300 K, which is attributed to the non-vanishing Berry phase arising from the non-collinear spin structure. Both the exchange bias and anomalous Hall effect in a wide temperature range of 5–300 K suggest that the Mn–Cr–Sn alloy has a promising application prospect in antiferromagnetic based spintronics devices.

    更新日期:2020-02-07
  • Study of the transition from self-organised to homogeneous plasma distribution in chromium HiPIMS discharge
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-07
    M Šlapanská, A Hecimovic, J T Gudmundsson, J Hnilica, W Breilmann, P Vašina and A von Keudell

    The self-organised plasma patterns, known as spokes or ionisation zones in magnetron sputtering discharges, were observed in a wide range of power densities, from low power direct current magnetron sputtering (dcMS) discharge to high power impulse magnetron sputtering (HiPIMS) discharge. For some target materials and non-reactive gases, it was observed that at very high power densities (> ##IMG## [http://ej.iop.org/images/0022-3727/53/15/155201/dab6a8cieqn001.gif] ) the plasma exhibits a transition from a regime where spokes are observed to a homogeneous plasma regime. In this contribution, we present a comparison of plasma properties: plasma emission (optical emission spectroscopy) and flux of argon and chromium ions (mass spectrometry), measured both in the spoke regime and in the homogeneous plasma regime, aimed to expand the understanding of the plasma transition between the two modes. A simple biased flat probe was used to distinguish between the s...

    更新日期:2020-02-07
  • Growth mechanism of highly oriented layered Sb 2 Te 3 thin films on various materials
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-07
    Françoise Hippert, Philippe Kowalczyk, Nicolas Bernier, Chiara Sabbione, Xavier Zucchi, Damien Térébénec, Cristian Mocuta and Pierre Noé

    Sb 2 Te 3 is a layered material with outstanding properties leading to applications in interfacial phase-change memories, spintronic and thermoelectric devices. For successful integration in devices, controlling the orientation of the atomic planes of Sb 2 Te 3 deposited by sputtering on various materials used for electrodes and on dielectric layers is required. We have succeeded in depositing Sb 2 Te 3 thin films (thickness in the range 10–100 nm) by sputtering in industrial deposition equipments on WSi, TiN, amorphous Si as well as on native and thermal silicon oxide layers. The structure and orientation of the films were studied by x-ray diffraction. The Sb and Te planes are found parallel to the substrate, whatever the nature of the bottom material, provided that the sputtering conditions avoid a Te deficiency in the deposited film. These results show that deposition of Sb 2 Te 3 with out-of-plane or...

    更新日期:2020-02-07
  • Realization of controllable acoustic acceleration beams via flexible active surfaces
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-07
    Peng-Qi Li, Ya-Xi Shen, Zhi-Guo Geng, Pei-Chao Cao, Yu-Gui Peng and Xue-Feng Zhu

    The generation of acoustic acceleration beams is a research hotspot that has attracted increasing interest recently. In this article, we propose to generate controllable acoustic acceleration beams by using a flexible active surface with homogeneous phase and amplitude distributions. Thus, the active surface does not necessarily require very complex electronic control systems. Analytically, we show that the beam trajectories can be related to the shape of flexible active surfaces via the technique of inverse Legendre transformation. Consequently, we can directly create diffraction-suppressed acoustic beams along curve trajectories in space. We numerically and experimentally demonstrate that the acoustic beam projected from a bent active surface propagates along the predesigned path, which is in good agreement with theoretical prediction. We envision that the active soft acoustic surface may have versatile applications in the fields of medical treatment, particle manipulation and...

    更新日期:2020-02-07
  • A high transmittance and fast response in-plane switching liquid crystal display with the zero-azimuth anchoring layers on the electrodes
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-07
    Osamu Sato, Harumi Okuno, Isao Adachi, Kohei Goto, Takahiro Noda and Kimiaki Tsutsui

    An in-plane switching (IPS) liquid crystal display (LCD) containing the zero-azimuth anchoring layers formed only on the electrodes and rubbed polyimide (PI) covered on the other areas was successfully developed. This configuration was realized using photoreactive PI with photo-radical generation units and the mask exposure technique. The maximum transmittance ( T max ) of this LCD was 1.12 times higher than that of a conventional IPS LCD. This was attributed to a large aperture in the voltage-on state because the nematic liquid crystals (NLCs) on the electrodes were barely anchored to the surface, such that the NLCs could be rotated by applying a small in-plane electric field above the electrodes, and by an elastic torque caused by the twisted NLCs between the electrodes. Furthermore, the response times of this LCD were equivalent to those of a conventional IPS LCD because the NLCs between the electrodes quickly recovered to their initial orientation after remov...

    更新日期:2020-02-07
  • A self-powered flexible-vision electronic skin based on piezophototronic GaN nanowires for rapid image recognition
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-07
    Tianming Zhao, Hongye Guan, Tianyan Zhong, Baodan Liu, Fei Liu, Lili Xing and Xinyu Xue

    A self-powered flexible-vision electronic skin for rapid image recognition has been fabricated from piezophototronic GaN nanowires. The basic structure of each photodetecting pixel consists of horizontally-aligned GaN nanowires crossing a cross-finger electrode, and 6 × 6 photodetecting pixels that form a patterned sensing matrix. The working mechanism is based on the piezophototronic effect, and the device can harvest a tiny amount of mechanical energy and directly output photodetecting signals without any external electrical power. The output piezoelectric voltage is significantly dependent on UV illumination, and the response is up to ~76 for 80 µ W cm −2 light. The response and recovery times are very short. A practical application of the device for rapid image recognition has been simply demonstrated, and this shows the potential for realizing an artificial intelligent retina. This work can promote the development of wearable flexible electronics and expan...

    更新日期:2020-02-07
  • Distributed vibration sensing with high frequency response by using WDM based integrated scheme
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-07
    Zhenshi Sun, Kun Liu, Junfeng Jiang, Pengfei Ma, Shuang Wang, Zhongyuan Xu, Hairuo Guo, Zichun Zhou, Tianhua Xu and Tiegen Liu

    Distributed vibration sensing measurement with high frequency response is still a challenging task in distributed optical fiber vibration sensing systems. In this paper, a WDM based integrated scheme is proposed to directly demodulate the high frequency vibration signal with high spatial resolution by merging the phase sensitive optical time-domain reflectometry and the Sagnac interferometer. A maximum frequency response of ~2.5 MHz and a spatial resolution of 20 m have been achieved in a 4 km sensing fiber link. Comparison to conventional sensing structure, the proposed scheme shows great application potential in the field of distributed vibration sensing system.

    更新日期:2020-02-07
  • Redefinition the quasi-Fermi energy levels separation of electrons and holes inside and outside quantum wells of GaN based multi-quantum-well semiconductor laser diodes
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-05
    Ding Li, Liefeng Feng, Wei Yang, Xiufang Yang, Xiaodong Hu and Cunda Wang

    Both accurate experiments and a self-consistent theoretical simulation using the near-ABC or ab initio method have uncovered the anomalous changes in the junction voltage ( V j ) of GaN-based lasers (Li et al 2013 Appl. Phys. Lett . 102 123501, Feng et al 2018 J. Phys. D: Appl. Phys . 51 095102 and Feng et al Appl. Phys . B 124 39). Here, further accurate emission spectral characteristics and band-gap simulation of a GaN based laser diodes (LDs) confirmed that previous researchers may have confused the junction voltage ( V j ) and the separation between the two Fermi levels of electrons and holes in the active region divided by the electronic charge (Δ E f / e ). For the multiple-quantum wells (MQWs), there are obvious differences between them. For an ideal GaN-based LDs, despite the increase in junction voltage, physical quantities includin...

    更新日期:2020-02-06
  • Reflective plasmonic super-oscillatory metasurfaces with simultaneous phase and amplitude controls for sub-diffraction focusing
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-05
    Dongliang Tang, Jia Liu, Long Chen, Jianjun Liu and Xiaohu Zhang

    Optical super-oscillatory phenomena, coming from the delicate interference of the propagating light through an elaborate-designed structure, have been successfully applied to realize far-field focusing and imaging with a resolution beyond the diffraction limit. However, most reported super-oscillatory lenses only modulate either the amplitude or phase of the incident light. Here, a reflective plasmonic super-oscillatory metasurface (RSOM), made of aluminum-nanorods/glass-spacer-layer/aluminum-mirror, is proposed to simultaneously engineer a desired amplitude and phase profile of the incoming light and realize far-field sub-diffraction focusing. The used reflective configuration with a high polarization conversion can be helpful to concentrate more energy into the super-oscillatory spot. Sub-diffraction hotspots are further numerically verified and precisely formed at the preset plane. The compressed spot sizes for one RSOM are 0.666 and 0.714 times the diffraction limit along th...

    更新日期:2020-02-06
  • Red persistent luminescence excited by visible light in CaS:Eu 2+ ,Tm 3+
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-05
    Yuki Tamura, Tsuyoshi Okuno, Yoriko Suda and Yasushi Nanai

    Excitation wavelength dependence of red persistent luminescence in ##IMG## [http://ej.iop.org/images/0022-3727/53/15/155101/dab6d1cieqn001.gif] phosphor is reported. Persistent luminescence appears under visible light excitation in the wavelength region of 400–600 nm. Photon energy from white light-emitting diode lamps is possibly stored in this material. This sulfide phosphor is synthesized using iodine vapor. Under iodine vapor, Eu 2+ and Tm 3+ are found to be efficiently included in CaS. The concentration dependence of Eu 2+ is studied, and the optimum concentration is 0.05%. Trap depth of 0.27–0.33 eV contributing to persistent luminescence is evaluated by using thermoluminescence.

    更新日期:2020-02-06
  • Orbital localization induced magnetization in nonmetal-doped phosphorene
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-05
    Le Huang, Peng Zhang, Nengjie Huo, Huafeng Dong, Hui-Xiong Deng, Zhongming Wei and Jingbo Li

    Density functional theory calculations are performed to explore the nature of magnetization in group-VI (O, S, Se, Te) and group-VII (F, Cl, Br, I) elements doped phosphorene monolayers. All these dopants, except for F, can introduce localized spin-polarized states in the gap of phosphorene, resulting in the magnetization of these systems. Orbital coupling analysis suggests that the distinct spin-polarization behaviors between group-VI-substituted and group-VII-substituted phosphorene result from the different orbital coupling between the dopants and neighboring P atoms. It is also demonstrated that the stability of magnetization, characterized by polarization energy, increases with the localization of spin-polarized bands. Our predictive results may inspire further experimental and theoretical exploration on the potential applications of doped 2D materials in spintronics.

    更新日期:2020-02-06
  • Enhancing local electric fields at plasmonic nanogaps by optimal dielectric coatings
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-05
    Liren Deng, Yanni Zhai, Yun Chen, Ningning Wang and Yu Huang

    Due to the generation of electromagnetic hot spots, metallic nanogaps have attracted great attention in various subjects, especially in plasmonics. For fixed nanogaps, using dielectric coating is an efficient way to narrow the gaps while improving their thermal and chemical stability. Herein, it is numerically demonstrated that the utilization of high refractive index dielectric coatings with zero or little loss, like TiO 2 , can lead to the generation of remarkable hot spots at the nanogaps. Two mechanisms work synergistically including the improved light coupling effect and a great leap of local electric field intensities at the dielectric-air interface. For higher refractive index dielectric coatings in practice, like graphene, despite a greater electric field leap at the interface, the weakening light coupling effect turns to play a dominant and negative role owing to the lossy dielectric properties. Our results provide a new perspective for the stabilization and fu...

    更新日期:2020-02-06
  • Low-magnetic-field controlled magnetodielectric coupling at room temperature in a chiral layered diphenylalanine-based 1D-coordination-polymer
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-05
    Jinlei Zhang, Shuyi Wu, Xiaobin Zhu, Jiancang Shen, Kede Ji and Ran Zhang

    Materials with low-magnetic-field control at room temperature is of fundamental importance for the practical application. Herein, a chiral 1D-coordination-polymer ([Ni(DPA) 2 (H 2 O)]) possessing coupled ferroelectric and ferromagnetic order is constructed. In addition, [Ni(DPA) 2 (H 2 O)] exhibits room-temperature ferroelectricity with giant magnetodielectric coefficency between −18% and −23% in the temperature range from 270 to 310 K, in nearly all measured frequencies, and under applied magnetic field as low as 0.5 T. The asymmetrical distortion of the coordination bond spurs electrical polarization and magnetodielectric effect, and reduces spin frustration in the octahedral geometry due to spin-lattice coupling. In addition, 2D nanosheets with non-centrosymmetric structure can be successfully exfoliated from [Ni(DPA) 2 (H 2 O)] microcrystals in retaining the morphological and structural integrity. This observation revea...

    更新日期:2020-02-06
  • Tunable metasurface with controllable polarizations and reflection/transmission properties
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-05
    Ruiqi Mao, Guangming Wang, Tong Cai, Haisheng Hou, Dengpan Wang, Borui Wu, Wenwu Zhang and Qing Zhang

    Metasurfaces attract significant attention and are widely applied in modern communication systems due to their powerful capabilities to control the polarization, amplitude, and phase of electromagnetic waves. However, it is considerably challenging to control polarization and amplitude of incident waves for a passive metasurface. Specifically, we integrate the transmission and reflection functions by loading a middle layer with PIN diodes while the upper and lower structures are used to manipulate the polarizations of incident waves. As a proof of concept, we fabricate a sample having 18 × 18 meta-atoms. Beam deflectors for the circularly polarized waves dependent on Helicity are realized when the PIN diodes are turned off. A transmissive polarization converter for x -polarization and a reflective polarization keeper for y -polarization are achieved as the PIN diodes are turned on. More importantly, the functionalities exhibit extremely high efficiencies in the ra...

    更新日期:2020-02-06
  • Introducing Huiyun Liu, Editor-in-Chief for Journal of Physics D: Applied Physics
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-05
    Huiyun Liu

    Description unavailable

    更新日期:2020-02-06
  • Deciphering the synergy between plasma and catalyst support for ammonia synthesis in a packed dielectric barrier discharge reactor
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-04
    Bhaskar S Patil, Alwin S R van Kaathoven, Floran J J Peeters, Nikolay Cherkasov, Jürgen Lang, Qi Wang and Volker Hessel

    Plasma-assisted ammonia synthesis in a packed dielectric barrier discharge (DBD) reactor at atmospheric pressure is presented in this work. A broad range of materials (commonly used as catalyst supports) with various chemical properties (acidic α -Al 2 O 3 , anatase TiO 2 and basic MgO, CaO), surface area and porosity ( α -Al 2 O 3 and γ -Al 2 O 3 ), dielectric properties (quartz wool, TiO 2 , and BaTiO 3 ), have been investigated for synergetic effects by packing them in the discharge zone of the DBD reactor. All the materials showed a substantial effect on ammonia production, which can be explained solely as a result of the effect of packing on plasma formation and not by a synergy between plasma and surface catalysis. Size and shape of packing material are found to be the key parameters in enhancing the performance. Quartz wool, closely followed by γ -Al 2 O ...

    更新日期:2020-02-04
  • The effect of metal-oxide incorporation on the morphology of carbon nanostructures
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-04
    Sebastian Tigges, Nicolas Wöhrl, Ulrich Hagemann, Marcel Ney and Axel Lorke

    Metal-organic, single-source, low-temperature, morphology-controlled growth of carbon nanostructures is achieved, using an inductively coupled plasma-enhanced chemical vapor deposition system. Three distinctive morphologies, namely nanoflakes, nanowalls (CNWs) and nanorods (and intermediates between these morphologies), can be reproducibly deposited, depending on the process parameters. The synthesized structures can be described as hybrid materials consisting of metal oxide incorporated in a carbon matrix material. Since the incorporation of metal oxide into the carbon structure significantly influences their growth, the synthesis cannot be described solely with the existing models for the growth of CNWs. Optical emission spectroscopy is used to measure the relative number density of suspected growth and etching species in the plasma, while physical and chemical surface analysis techniques (scanning electron microscopy, Raman spectroscopy, scanning Auger microscopy and x-ray ph...

    更新日期:2020-02-04
  • Tunable broadband terahertz metamaterial absorber using multi-layer black phosphorus and vanadium dioxide
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-02-04
    Tongling Wang, Lizhi Qu, Lingfei Qu, Yuping Zhang, Huiyun Zhang and Maoyong Cao

    We propose a dual-controlled switchable broadband metamaterial sandwich-structured absorber composed of black phosphorus (BP) and vanadium dioxide (VO 2 ), suitable for operation in the terahertz range. The proposed absorber consists of multi-layered sinusoidally patterned BP, sandwiched between dielectric layers, and a VO 2 bottom layer. Numerical results reveal that the broadband absorption can be dynamically tuned over a wide range by adjusting the electron doping of BP and conductivity of VO 2 . Owing to the fully metallic state of VO 2 , the proposed absorber realizes a more than 98% absorptance with the bandwidth of 2.9 THz under TE polarization and more than 90% absorptance with the bandwidth of 3.25 THz under TM polarization when the armchair direction of BP is along the y -axis and x -axis, respectively. Most importantly, by utilizing the dual independent controls in tandem, the state of proposed absorber can be switched...

    更新日期:2020-02-04
  • Diffusion behaviors of energy and momentum for 1D single-walled carbon nanotubes
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-28
    Nianbei Li

    The single-walled carbon nanotube (CNT) is a quasi-1D material with ultra high thermal conductivity. It is known that the heat conduction is closely related with the energy diffusion and the information of heat conduction can be obtained by examining the energy diffusion behavior. The correlated energy distribution C E ( i , t ) calculated in diffusion process gives the whole spatial distribution of energy spreading at every correlation time which is much better than the traditional heat conduction method where only a number of thermal conductivity is provided. In previous study the anomalous super-diffusion of energy has been reported for CNT via a non-equilibrium diffusion method. Here we apply the more sophisticate equilibrium diffusion method to investigate the energy diffusion behavior in CNT with much longer length up to ##IMG## [http://ej.iop.org/images/0022-3727/53/14/145302/dab69adieqn001.gif] m with much highe...

    更新日期:2020-01-30
  • The impact of laser energy, bias and irradiation positions on single event transients of InP HBT
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-28
    Xiao-Hong Zhao, Hong-Liang Lu, Yu-Ming Zhang, Yi-Men Zhang and Zhi-Chao Wei

    The mechanism of single event transients in indium phosphide heterojunction bipolar transistors are studied with different laser energy, collector and irradiation positions based on a pulsed laser experiment. The area of the depletion region neutralized by the laser track determines the area of the funnel region, and affects the total charges collected by collector Q Total . The total charge collection consists of the charge collected in the depletion region, the charges collected in funnel region, and the diffusion charges. The larger the area of the neutralized depletion region, the larger the area of the funnel region, thus, the more electron–hole pairs would be collected. The influence of laser energy, collector bias and irradiation positions on total charge collection is studied and discussed in detail.

    更新日期:2020-01-30
  • Radiofrequency phase resolved electron density measurements with the hairpin resonator probe
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-23
    D J Peterson, K Ford, J Brandon, S C Shannon, T Koh, T C Chua, K Bera, W Tian, S Rauf and P A Kraus

    A floating hairpin resonator probe is used to measure electron density within the radiofrequency cycle of a parallel plate capacitively coupled plasma at steady state. A time resolution capable of detecting electron density oscillations within the radiofrequency cycle is demonstrated. Electron density oscillations are observed at the drive frequency over a range of operating conditions including 10–250 mTorr (1.3–33 Pa) in argon driven at 13.56 or 27.12 MHz. Localized electron density oscillation amplitudes show moderate agreement with literature and fluid simulations near the powered electrode and disagreement in the plasma bulk. The technique is useful for studying electron heating mechanisms in radiofrequency discharges due to its high time resolution.

    更新日期:2020-01-23
  • Evaluation for multiple processing parameters in selective laser melting based on an integration of mesoscale simulation and experiment method
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-23
    Zhichao Dong, Weijie Li, Qi Zhang, Yabo Liu, Jingran Ge, Xiaohu Lin and Jun Liang

    Selection reasonable processing parameters for the metallic product by selective laser melting (SLM) is a significant issue to improve the performance of the final product. The optimization for the performance of the product is caused by the comprehensive effect of multiple processing parameters instead of a single parameter. It is urgent to propose a method for evaluating this comprehensive effect, furthermore, providing reasonable processing parameters. In this study, the mesoscopic features (molten pool morphology, free surface, porosity distribution, etc.) under different processing parameters are analyzed. Meanwhile, a powder scale thermal-fluid coupled model is established considering the randomly distributed powder bed and the complex physical phenomena within the molten pool. The simulation results are compared with the results characterized by multiple experimental methods. The integration of simulation and experiment results show that a fast scanning velocity or a larg...

    更新日期:2020-01-23
  • The plasma enhanced surface reactions in a packed bed dielectric barrier discharge reactor
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-23
    He Cheng, Mingyu Ma, Yanzhe Zhang, Dawei Liu and Xinpei Lu

    The conversion and utilization of CO 2 is one of the greatest global challenges. Plasma assisted catalysis provide a new resolution to this problem. However, the energy efficiency and conversion rates of the plasma process are still insufficient for industrial applications. The key reasons are the highly complex interaction between gaseous plasma and catalytic materials, especially in packed bed dielectric barrier discharges. Our study fills this critical gap by developing a novel numerical approach to study how the ns pulse driving plasma trigger the heterogeneous reactions on the Ni/ γ -Al 2 O 3 catalyst surface. The development of plasma inside the reactor is in the form of surface ionization wave (SIW) + filamentary microdischarges. The high electron power in the SIW region and the high ion power density in the sheath region on the catalysts surface provide enough energy to trigger heterogenous reactions. The heterogeneous reactions not on...

    更新日期:2020-01-23
  • Filler fluorination of nanoTiO 2 /ER composites and their surface insulation properties: a comparison of dielectric barrier discharge and chemical solution fluorination
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-23
    Hao-Ou Ruan, Qing Xie, Fang-Cheng Lü, Zhen-Yu Zhan, Ji-Yuan Yan, Liu-Cheng Hao and Quan-Sheng Zhu

    NanoTiO 2 /epoxy resin composites, a kind of dielectric materials with excellent thermal, mechanical and electrical properties, has extensive promise in the insulation area of power system. Although the semiconductor property of TiO 2 filler can suppress the electric field mutations in the epoxy insulation devices, the doping of TiO 2 will have bad influence on the charge transmission, thus weakening the surface insulation. To solve this problem, filler fluorination with dielectric barrier discharge (DBD) plasma and chemical methods were designed to modify the TiO 2 filler. The effects of two fluorination methods on the micro-structures, electrical parameters, and insulation properties of the materials were studied. The results have shown that both DBD plasma and chemical fluorination methods can effectively introduce fluorine into TiO 2 filler and its epoxy composites, decreasing its dielectric constant and volume resistivity. Th...

    更新日期:2020-01-23
  • Nanosecond-pulsed dielectric barrier discharge-based plasma-assisted anti-icing: modeling and mechanism analysis
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-23
    Yifei Zhu, Yun Wu, Biao Wei, Haojun Xu, Hua Liang, Min Jia, Huimin Song and Yinghong Li

    The characteristics of nanosecond-pulsed dielectric barrier discharge (nSDBD) in an anti-icing configuration is studied. The mechanisms and energy characteristics of the nSDBD-based plasma-assisted anti-icing are analyzed using a numerical model and existing experimental data. Two-dimensional simulations based on PASSKEy (PArallel Streamer Solver with KinEtics) code are conducted. The code couples a self-consistent fluid model with detailed kinetics, an efficient photo-ionization model, Euler equations and a heat transfer equation for solid materials. The results of icing wind tunnel experiments conducted by two groups are analyzed together. The reduced electric field and the electron density are examined for high-voltage pulses with 800 ns and 20 ns width. The ‘merge’ of counter-propagating surface streamers with the same polarity is numerically observed under high-voltage amplitude. The effects of gas heating and solid heating in time scales of one pulse and one duty cycle are...

    更新日期:2020-01-23
  • Multiple anisotropic conductions, up/down conversion luminescence and magnetism assembled into 2D step-like Janus array film
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-23
    Jiao Tian, Qianli Ma, Wensheng Yu, Dan Li, Xiangting Dong, Guixia Liu and Jinxian Wang

    A novel 2D dual-layer step-like Janus array film (DSJAF) based on 1D Janus nanoribbon and Janus microfiber as structural units is devised and fabricated by combining conjugate with parallel electrospinning. In DSJAF, the top-layer Janus nanoribbon array film covers the left half of the bottom-layer Janus microfiber array film and the two films bind together to form the step-like composite film, achieving two sets of Janus structures, respectively, from top to bottom on the left half of the DSJAF and from left to right on the top surface of the DSJAF. The specially structured DSJAF exhibits two sets of double anisotropic conduction coming from the two sets of Janus structures, and single anisotropic conduction exists, respectively, in the top-layer film and bottom-layer film, realizing multiple anisotropic conductions. The conductive anisotropic degree of DSJAF is modulated by diverse structural units of Janus microfiber and Janus nanoribbon. Up-conversion luminescence (UCL) and ...

    更新日期:2020-01-23
  • Fabrication of ordered Sb–Te and In–Ge–Te nanostructures by selective MOCVD
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-23
    R Cecchini, C Martella, A Lamperti, S Brivio, F Rossi, L Lazzarini, E Varesi and M Longo

    The controlled growth of chalcogenide nanoscaled phase change material structures can be important to facilitate integration and to enable complex architectures for phase change memory and other microelectronic applications. Here, the growth of Sb–Te and In–Ge–Te alloys by metal–organic chemical vapour deposition (MOCVD) on patterned substrates featured with an array of recesses (~130 nm features width) was investigated. High selectivity, with preferential growth on a CoSi 2 metallic layer at the recess bottom with respect to the surrounding SiO 2 masking layer, was obtained, leading to a single-step fabrication of arrays of high-aspect-ratio chalcogenide nanostructures. The growth selectivity, as well as the morphology, composition and microstructure of the grown nanostructures, as a function of the different MOCVD process parameters, were investigated by scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, Ra...

    更新日期:2020-01-23
  • New low loss soft thermoplastic blends for microwave applications
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-22
    Tessnim Sghaier, Mohammed El Gibari and Benoit Guiffard

    All organic soft dielectrics are growing more and more interest in the electronic industry owing to their light weight, low cost and the flexibility they yield compared to the rigid devices. In the specific field of microwave communicating devices planar printed (patch) antennas on a soft dielectric substrate are sought for their conformability and advantageous compactness. In this article, two soft thermoplastic elastomer blends based on polypropylene (PP) or low-density polyethylene (LDPE) were tested. The fabrication process and the established characterization steps have been fully presented. More specifically, in order to characterize the dielectric film up to 40 GHz, the microstrip ring resonator with coplanar waveguide access has been adapted to a new configuration specimen sample. The results of the characterizations obtained showed very encouraging performances for microwave applications. Indeed, the measured dielectric constant and loss tangent up to 40 GHz were found ...

    更新日期:2020-01-23
  • Enhanced chemical etch rate of borosilicate glass via spatially resolved laser-generated color centers
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-22
    A A Serkov and H V Snelling

    In this work, it is shown that controllable increases in chemical reactivity of borosilicate glass can be induced through spatially resolved femtosecond laser irradiation at fluence values significantly lower than the damage threshold. The hydrofluoric acid etch rate has been found to be closely correlated to the reduction in optical transmission of the glass at 488 nm, which is, in turn, governed by the production of boron–oxygen hole centers. The combination of laser irradiation below the ablation threshold followed by chemical etching is shown to yield surfaces that have a roughness lower than those achieved by either laser or chemical etching alone. Application of this effect to the manufacture of freeform Laplacian optics is demonstrated.

    更新日期:2020-01-23
  • Nanosecond second harmonic generation for electric field measurements with temporal resolution shorter than laser pulse duration
    J. Phys. D: Appl. Phys. (IF 2.829) Pub Date : 2020-01-22
    Igor V Adamovich, Tom Butterworth, Thomas Orriere, David Z Pai, Deanna A Lacoste and Min Suk Cha

    Electric field induced second harmonic (EFISH) generation using a ns pulse duration laser has been employed for time-resolved measurements of the axial and transverse electric field in a pin-to-pin ns pulse discharge in ambient air, at atmospheric pressure and at 2 bar. The results demonstrate that the time-varying electric field can be measured accurately over the duration of the laser pulse 15–20 ns long, with the temporal resolution (potentially sub-ns) limited by the response time of the detector. Each data set provides time-accurate electric field over a period of up to 10 ns. Time-resolved electric fields over longer time periods are measured by adjusting the laser Q-switch delay, and using the composite data obtained by overlapping the individual data sets. Absolute calibration of the electric field is obtained from the comparison of the experimental data with the Laplacian field distribution in the discharge gap before breakdown, taking into account the residual charge a...

    更新日期:2020-01-23
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