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In this paper, the thermoelectric (TE) properties of Janus MXY monolayers (M = Pd, Pt; X, Y = S, Se, Te) are systematically studied using first principles and the Boltzmann transport theory. The thermal conductivity (k), Seebeck coefficient (S), power factor (PF), and TE figure of merit (ZT) are calculated accurately for various carrier concentrations. The lattice thermal conductivities of these six materials sequentially decrease in the order PtSSe, PtSTe, PtSeTe, PdSSe, PdSTe, and PdSeTe. PdSeTe and PtSeTe monolayers have a high ZT close to one at 300 K. In addition, we predicted the TE properties at high temperatures and found that the maximum ZT (2.54) is achieved for a monolayer of PtSeTe at 900 K. The structural and electronic properties of these six Janus transition-metal dichalcogenide (TMD) monolayers were systematically studied from first principles. Our results show that all six materials are semiconductors with bandgaps between 0.77 eV and 2.26 eV at the Heyd-Scuseria-Ernzerhof (HSE06) level. The present work indicates that the Janus MXY TMD monolayers (M = Pd, Pt; X, Y = S, Se, Te) are potentially TE materials. [ABSTRACT FROM AUTHOR]

We systematically investigate the thermoelectric properties of lanthanum phosphide (LaP) using first-principles calculations together with the Boltzmann transport theory. The dynamic stability of LaP is confirmed based on phonon dispersion. The different atomic masses of La and P atoms lead to an acoustic-optical bandgap that prohibits scattering between acoustic and optical phonon modes. The lattice thermal conductivity κ l is 3.19 W/mK at room temperature, which is less than that of LaAs because of the smaller group velocities and the larger Grüneisen parameter. The calculated phonon-mode contribution to κ l , scattering rate, and mean free path may provide significant guidance to further theoretical and experimental research. The power factor reaches 0.012 W m−1 K−2 at a carrier concentration of 1.05 × 10 20 c m − 3 , which is comparable to the power factor of the typical thermoelectric material Bi2Te3. This reasonable power factor and thermal conductivity suggest that LaP is a promising thermoelectric material. The dependence of the figure of merit ZT on carrier concentration n and temperature T indicates that a high ZT can be obtained by increasing the temperature and tuning the carrier concentration. [ABSTRACT FROM AUTHOR]

The effects of indentation-induced dislocations on spectroscopic performances of CdZnTe detectors and on the deep-level defects of CdZnTe crystals are studied. The mobility-lifetime product (ls) for electrons of the as-grown sample is determined to be 1.2×10-3 cm2/V by the γ-ray energy spectral measurement. However, the value reduced to 4.5×10-4 cm2/V after the dislocation is artificially increased by indentation. Meanwhile, the energy resolution is deteriorated from 7.45% to 28.15%. The ion beam induced charge (IBIC) measurements showed quite low carrier collection efficiency of electrons in the dislocation enriched areas. Moreover, the carrier recombination rate at dislocations was reduced with the increase in applied voltage. The thermally stimulated current measurements showed that the concentration of dislocation related defect levels observed at 0.107 eV and 0.159 eV increased almost twice after indentation. These defect levels could probably result in the carrier loss during the γ-ray energy spectrum and IBIC measurements. [ABSTRACT FROM AUTHOR]

This study demonstrates well-designed tri-layer flexible transparent conducting electrodes (TCEs), whose structure is ZnO (20 nm)/Ag grids (4, 6, 8, 10 nm)/ZnO (20 nm) (ZAZ), fabricated via thermal deposition. The optical, electrical, and mechanical characteristics of the proposed structure are improved compared to those of MoO3/Ag grids/MoO3 (MAM) electrodes. The transmittance at 550 nm, sheet resistance, and figure of merit of the proposed ZAZ electrodes with 6-nm silver grids are 78.58%, 9.3 Ω/square, and 9.6 x 10-3, respectively, which are better than those of MAM electrodes (66.25%, 9.7 X/square, and 1.6 x 10-3, respectively). It is found that the enhancement of the electrical characteristics of ZAZ can be ascribed to the improved crystallization of ZnO films. ZnO films with improved crystallization and a larger grain size can inhibit carriers from scattering at inter-grain boundaries. Based on a bending test, the strains of ZAZ electrodes under tension and compression were 0.616%, 0.633%, and those of MAM electrodes were 0.62% and 0.65%, respectively. The sheet resistance of the ZAZ structure increases significantly after 800 bending cycles, while that of the MAM structure increases significantly after only 200 bending cycles. These data indicate that ZAZ electrodes have significantly improved mechanical properties and durability compared to those of MAM electrodes in the bending test under both tensile and compressive stress. The proposed TCEs show good optical, electrical, and mechanical characteristics and have potential for application in optoelectronics. [ABSTRACT FROM AUTHOR]

We identify by ab initio calculations a new simple cubic carbon phase in Pa3 symmetry, which has a 48-atom unit cell in all-sp³ bonding networks, thus termed SC48 carbon. It can be viewed as a crystalline form of C12 clusters or a combined structure of SC24 and BC12 carbon, but it is energetically more stable than the recently reported cubic carbon phases such as BC8, SC24, BC12, and fcc-C12. The structural stability is verified by phonon mode analysis. Electronic band and density of state calculations reveal that SC48 carbon is an insulator with a large direct band gap of 4.40 eV. Moreover, simulated x-ray diffraction patterns provide an excellent match to the distinct diffraction peaks found in milled fullerene soot. These results provide a solid foundation for further exploration of this new carbon allotrope. [ABSTRACT FROM AUTHOR]

In this paper, the authors report rationally designed, innovative tri-layer flexible transparent conductive electrodes (TCEs) fabricated via thermal deposition. The proposed structure improves transparency compared with that of the traditional tri-layer electrode (dielectric/metal film/dielectric) by using metallic grid patterns (dielectric/metal grids/dielectric). The obtained MoO3/Ag grids/MoO3 TCEs show low sheet resistance and good mechanical properties. The sheet resistance of the proposed electrodes is 5.88 Ω/square and the transmittance reaches 76.5%, which are better than those of conventional MoO3/Ag film/MoO3 electrodes (6.12 Ω/square, <70%). The mechanical properties are significantly improved compared with those of MoO3/Ag film/MoO3 in the bending test under both tensile and compressive stress. The surface features of the MoO3/Ag grids/MoO3 TCEs were measured using the contact angle method to calculate the surface energy and polarity. The polarity is 0.5-0.26, which is better than those of indium tin oxide (0.35) and MoO3/Ag film/MoO3 (0.5-0.0058) electrodes for 0-800 bending cycles. The proposed flexible transparent electrodes show good optical, electrical, and mechanical characteristics and have potential for application in optoelectronics. [ABSTRACT FROM AUTHOR]

The Ni contact layer was deposited on semi-insulating 4H-SiC substrate by magnetron sputtering. The as-deposited samples were treated by rapid thermal annealing (RTA) and KrF excimer laser thermal annealing (LTA), respectively. The RTA annealed sample is rectifying while the LTA sample is Ohmic. The specific contact resistance (ρc) is 1.97 × 10-3 Ω·cm2, which was determined by the circular transmission line model. High resolution transmission electron microscopy morphologies and selected area electron diffraction patterns demonstrate that the 3C-SiC transition zone is formed in the near-interface region of the SiC after the as-deposited sample is treated by LTA, which is responsible for the Ohmic contact formation in the semi-insulating 4H-SiC. [ABSTRACT FROM AUTHOR]

We theoretically and numerically investigate a low-power, ultrafast, and dynamic all-optical tunable plasmonic analog to electromagnetically induced transparency (EIT) in two nanodisk resonators side-coupled to a metal-insulator-metal plasmonic waveguide system. The optical Kerr effect is enhanced by the slow light effect of the plasmonic EIT-like effect and the plasmonic waveguide based on graphene-Ag composite material structures with giant effective Kerr nonlinear coefficient. The optical Kerr effect modulation method is applied to improve tuning rate with response time of subpicoseconds or even femtoseconds. With dynamically tuning the propagation phase of the plasmonic waveguide, π-phase shift of the transmission spectrum in the plasmonic EIT-like system is achieved under excitation of a pump light with an intensity as low as 5.85 MW/cm2. The group delay is controlled between 0.09 and 0.4 ps. All observed schemes are analyzed rigorously through finite-difference time-domain simulations and coupled-mode formalism. Results show a new direction toward the low power consumption and ultrafast responses of integration plasmonic photonic devices and all-optical dynamical storage of light devices in optical communication and quantum information processing. [ABSTRACT FROM AUTHOR]

In this work, the composition dependence of high-frequency magnetic properties for the oriented hcp-Co1-xIrx soft magnetic films with negative uniaxial magnetocrystalline anisotropy (Kugrain) and in-plane uniaxial anisotropy field (Hu) is investigated. Both the saturation magnetization (Ms), Kugrain, and Hu are greatly affected by the composition of Ir. The (μi - 1) . fr of Co1-xIrx (with negative Kugrain) is larger than Acher's limit (without Kugrain) when x exceeds 0.14. The increasing percent of (μi - 1) . fr could get a maximum of 42% when x is 0.2. [ABSTRACT FROM AUTHOR]

Using a combination of Ag-coated hollow glass spheres (HGS@Ag) and a small quantity of graphene sheets within the epoxy matrix, we have prepared a novel lightweight high efficiency microwave absorption composite. Compared with pure HGS@Ag and graphene composite, the -10 dB absorption bandwidth and the minimum reflection loss of the novel composite are improved. Reflection loss exceeding -20 dB is obtained for composites in a wide frequency range and the minimum reflection loss reaches -46 dB while bandwidth less than -10 dB can reach up to 4.1GHz when an appropriate absorber thickness between 2 and 3.5mm is chosen. The enhanced microwave absorption performance of the novel composite is due to the enhanced dielectric response, enhanced conductivity, and the trap of electromagnetic radiation with increased propagation paths by multiple reflections. [ABSTRACT FROM AUTHOR]

The temperature-controlled surface-assisted synthesis of halogen bonded, organometallic, and covalent nanostructures based on 1,3,5-tribromo-benzene (TriBB) was studied with scanning tunneling microscopy and X-ray photoemission spectroscopy in ultrahigh vacuum. Vapor deposition of TriBB onto a Cu(111) surface held at 90 K leads to the formation of large domains of a honeycomb-like organic monolayer structure stabilized by triangular nodes with Br...Br intermolecular bonds. Upon annealing the organic monolayer to ~140 K, a new hexagonal close-packed structure with intact TriBB molecules connected by Cu adatoms is formed. Further warming up the sample to 300 K gives rise to the scission of C-Br bonds and formation of C-Cu-C bonds between phenyl fragments such that stable dendritic organometallic networks are formed. Larger islands of organometallic networks are obtained by maintaining the temperature of Cu(111) at 420 K during deposition of TriBB. Simultaneously, large islands of Br atoms are formed around the organometallic networks. Annealing the more extended organometallic network (prepared at 420 K) to 520 K leads to the formation of a branched covalent organic framework (COF) which comprises structural elements of porous graphene and is surrounded by Br islands. These organometallic networks and COFs appear as small dendritic and branched domains, most likely due to the steric influence exerted by the Br islands. [ABSTRACT FROM AUTHOR]

In this paper, low-power and ultrafast all-optical tunable plasmon induced transparency in metal-dielectric-metal (MDM) waveguide side-coupled Fabry-Perot (FP) resonators system with nonlinear optical Kerr medium is investigated both analytically and numerically. High tunability in transparency window magnitude and phase responses is obtained when nonlinear optical Kerr material is embedded in the MDM waveguide. In order to reduce the pump intensity, traditional nonlinear optical Kerr material is replaced by graphene. A shift of 64 nm in the central wavelength of the transparency window is achieved when the FP resonators are covered with monolayer graphene with pump intensity increasing from 9.2 to 10 MW/cm2. An ultrafast response time of the order of 1 ps is reached because of ultrafast carrier relaxation dynamics of graphene. This work not only paves the way towards the realization of on-chip integrated nanophotonic devices but also opens the possibility of the construction of ultrahigh-speed information processing chips based on plasmonic circuits. [ABSTRACT FROM AUTHOR]

The defect levels and carrier lifetime in CdZnTe: In crystal were characterized with photoluminescence, thermally stimulated current measurements, as well as contactless microwave photoconductivity decay (MWPCD) technique. An evaluation equation to extract the recombination lifetime and the reemission time from MWPCD signal is developed based on Hornbeck-Haynes trapping model. An excellent agreement between defect level distribution and carrier reemission time in MWPCD signal reveals the tail of the photoconductivity decay is controlled by the defect level reemission effect. Combining 241Am gamma ray radiation response measurement and laser beam induced transient current measurement, it predicted that defect level with the reemission time shorter than the collection time could lead to better charge collection efficiency of CdZnTe detector. [ABSTRACT FROM AUTHOR]

A map displaying the matching characteristics and absorption performance for the metallic carbonyl iron composite in microwave frequency band is developed based on the origin of absorption peaks. In this map, the dependence of matching frequency fm on absorber thickness, input impendence, and absorption peak value is achieved simultaneously from the complex permeability and permittivity spectra without any approximation. From this map, the perfect matching frequency fpm and perfect matching thickness tpm at input impendence Z=1 can be directly searched. Moreover, the required absorber thickness and the reflection loss value at any expected frequency where the absorption peak locates can be directly observed. [ABSTRACT FROM AUTHOR]

The micro fluxgate sensors have shown high sensitivity for the magnetic beads detection. For portable magnetic biological detection, Co-based amorphous ribbons with high permeability and low saturation magnetic induction are chosen as core materials to lower the operation requirements of the fluxgate-based magnetic beads detection. The micro fluxgate sensors with single-layer core and bi-layer core are fabricated by Micro-Electro-Mechanical System technologies, which exhibit a power consumption of 10.88 mW and 24.48 mW, a sensitivity of 1644V/T and 1456V/T, and a noise of 1.66 nT/Hz1/2 @1Hz and 2.32 nT/H1/2 @1Hz, respectively. The Dynabeads with concentrations of 300 &#181g/ml in 10 µl are detected by the micro fluxgate-based sensing system based on static response, and the results show signal change ratio of 12.2% and 9.2% under the max signal difference at 215 µT and 480 µT of the bias magnetic field for two kinds of the sensors, respectively, which is near the saturation point of the sensors. The fluxgate-based bead detection system with Co-based ribbon core presents low demands for the bias magnetic field and power consumption. [ABSTRACT FROM AUTHOR]

We theoretically propose a dynamic and ultrafast group delay tuning mechanism in two microcavities side-coupled to a waveguide system through external optical pump beams. The optical Kerr effect modulation method is applied to improve tuning rate with response time of subpicoseconds or even femtoseconds. The group delay of an all-optical analog to electromagnetically induced transparency effect can be controlled by tuning either the frequency of photonic crystal microcavities or the propagation phase of line waveguide. Group delay is controlled between 5.88 and 70.98 ps by dynamically tuning resonant frequencies of the microcavities. Alternatively, the group delay is controlled between 1.86 and 12.08 ps by dynamically tuning the propagation phase of line waveguide. All observed schemes are analyzed rigorously through finite-difference time-domain simulations and coupled-mode formalism. Results show a new direction toward microstructure integration optical pulse trapping and all-optical dynamical storage of light devices in optical communication and quantum information processing. [ABSTRACT FROM AUTHOR]

High quality 431 steel coatings were prepared on a 27SiMn substrate by extreme-high-speed laser cladding (EHLA) and conventional laser cladding (CLA), respectively. The cladding speed of the EHLA process was 150 m/min, and the surface rate could reach up to 1.14 m2/h, which is four times higher than that of the CLA process. The microstructure of the coatings was investigated in detail. The microstructure of both coatings was dominated by dendrites. Benefitting from the ultrahigh cooling rate, the dendrites of EHLA coatings were more refined than that of CLA coatings. The element distribution between dendrites and interdendritic regions was more uniform. The corrosion resistance was evaluated by electrochemical tests. The results indicated that the EHLA coatings performed better corrosion resistance due to the fine uniform microstructure. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Chemical Physics (1674-0068) is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We investigated the operation of an all-optical rubidium-87 atomic magnetometer with amplitude-modulated light. To study the suppression of spin-exchange relaxation, three schemes of pumping were implemented with room-temperature and heated paraffin coated vacuum cells. Efficient pumping and accumulation of atoms in the F=2 ground state were obtained. However, the sought-for narrowing of the resonance lines has not been achieved. A theoretical analysis of the polarization degree is presented to illustrate the absence of light narrowing due to radiation trapping at high temperature. [ABSTRACT FROM AUTHOR]

The Fe-doped lead-free 0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3 single crystal, reported in the previous work, which exhibited giant piezoelectric strain response (normalized strain constant up to ~1300 pm/V) and a large quasi-static piezoelectric constant d33 of ~600 pC/N, was investigated here with the emphasis on the domain structure so as to understand the nanoscale mechanism responsible for the giant strain response. Based on in-plane and out-of-plane piezoresponse force microscopy, it was found that Fe ion doping induced domain evolution from macrodomains of several micrometers to nanodomains of tens of nanometers. High-resolution transmission electron microscopy was adopted to give an insight into the fine domain structure after Fe doping. The domain evolution under an in situ electric field was further studied, and the results indicated that the giant strain response originated not only from the polarization rotation around the morphotropic phase boundary but also from the domain contribution. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Chemical Physics (1674-0068) is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We report a high frequency ultrasonic transducer up to 50MHz for vessel imaging based on a leadfree (K0.44Na0.56)NbO3-0.5 mol. % Mn (Mn-KNN) single crystal, which has a high electromechanical coupling coefficient kt of 0.64 and a large thickness frequency constant Nt of 3210 kHz ⋅ mm. The Krimholtz, Leedom, and Mattaei (KLM) equivalent circuit model was utilized to simulate and optimize the pulse-echo response combined with PiezoCAD software. Theoretically, a high -6 dB bandwidth of 74.94% was obtained at a center frequency of 50.47MHz and optimized matching conditions. The experimental results showed a center frequency of 51.8MHz with a -6 dB bandwidth of 70.2%. The excellent global performance makes this lead-free single-crystal transducer quite potential in an environmentally friendly vessel imaging transducer. [ABSTRACT FROM AUTHOR]

Organometal halide perovskite is a promising material to fabricate light-emitting diodes (LEDs) via solution processing due to its exceptional optoelectronic properties. However, incomplete precursor conversion and various defect states in the perovskite light-emitting layer lead to low luminance and external quantum efficiency of perovskite LEDs. We show here the addition of an optimum amount of sodium bromide in the methylammonium lead bromide (MAPbBr3) precursor during a one-step perovskite solution casting process can effectively improve the film coverage, enhance the crystallinity, and passivate ionic defects on the surface of MAPbBr3 crystal grains, resulting in LEDs with a reduced turn-on voltage from 2.8 to 2.3V and an enhanced maximum luminance from 1059 to 6942 Cd/m² when comparing with the pristine perovskite-based device. [ABSTRACT FROM AUTHOR]

The development of cost-effective gas sensors with improved sensing properties and minimum power consumption for room temperature hydrogen leakage monitoring is in increasing demand. In this context, this report focus on the facile fabrication of ordered mesoporous TiO2 via evaporation-induced self-assembly route. With the controlled doping threshold (3%Co-TiO2), the output resistance change to 1000 ppm H2 is ~4.1×103 with the response time of 66 s. The sensor response exhibits power law dependence with an increase in the hydrogen concentration, where the power law coefficient was found not only specific to the kind of target gas but also related to temperature. Further, the effect of structure integrity with doping level and humidity on sensing characteristics is interpreted in terms of variation in surface potential eVS and depletion region w caused by the adsorption of molecular oxygen O2- 2 . [ABSTRACT FROM AUTHOR]

Spin-orbit torques (SOTs) in Ta/CoFeB/MgO structures are studied by harmonic voltage method. The results indicate that both Slonczewski-like (HSL) and field-like (HFL) effective field are enhanced by annealing in the film stacks with various Ta thicknesses. Investigation of the crystallographic phase of the Ta layers and resistance of Hall bar devices suggest that annealing may induce a phase transformation in the Ta layers from the α to the β phase, which results in the enhanced HSL of the annealed samples. Current-induced magnetization switching experiments revealed a corresponding decrease of the switching current in the annealed samples because of their enhanced SOTs. [ABSTRACT FROM AUTHOR]

The characteristics of MoS2-nanoflake field-effect transistors (FETs) were studied by analyzing the transfer curves in MoS2-FETs with ferroelectric and general polymers as the gate dielectric. A clear hysteresis, opposite to the electron trapping-detrapping effect in traditional MoS2-FETs, was observed in the MoS2-FETs with ferroelectric poly(vinylidene fluoride/trifluoroethylene) [P(VDF-TrFE)] films. The effect carrier mobility of MoS2 nanoflakes reached approximately 95.6 cm²/Vs under the control of the polarization field of P(VDF-TrFE), whereas the effect carrier mobility was only approximately 15.3 cm²/Vs in MoS2-FETs with traditional dielectric poly(methyl methacrylate) (PMMA) films. Furthermore, the ferroelectric MoS2-FETs possess a higher ON/OFF resistance ratio (approximately 107) than do the PMMA MoS2-FETs (approximately 105). [ABSTRACT FROM AUTHOR]

Bouncing dynamics of impact droplets on solid surfaces intensively appeal to researchers due to the importance in many industrial fields. Here, we found that droplets impacting onto dome convex superhydrophobic surfaces could rapidly bounce off with a 28.5% reduction in the contact time, compared with that on flat superhydrophobic surfaces. This is mainly determined by the retracting process of impact droplets. Under the action of dome convexity, the impact droplet gradually evolves into an annulus shape with a special hydrodynamic distribution. As a consequence, both the inner and external rims of the annulus shape droplet possess a higher retracting velocity under the actions of the inertia force and the surface energy change, respectively. Also, the numerical simulation provides a quantitative evidence to further verify the interpretation on the regimes behind the rapidly detached phenomenon of impact droplets. [ABSTRACT FROM AUTHOR]

In this work, we reported a large magnetoresistance effect in silicon by ion implantation of nitrogen atoms. At room temperature, the magnetoresistance of silicon reaches 125 % under magnetic field 1.7 T and voltage bias -80 V. By applying an alternating magnetic field with a frequency (f ) of 0.008 Hz, we find that the magnetoresistance of silicon is divided into f and 2f two signal components, which represent the linear and quadratic magnetoresistance effects, respectively. The analysis based on tuning the magnetic field and the voltage bias reveals that electric-field-induced space-charge effect plays an important role to enhance both the linear and quadratic magnetoresistance effects. Observation as well as a comprehensive explanation of large MR in silicon, especially based on semiconductor CMOS implantation technology, will be an important progress towards magnetoelectronic applications. [ABSTRACT FROM AUTHOR]

This paper demonstrates an online measurement technique which can measure both surface tension and viscosity for confined fluids in microfluidic systems. The surface tension and viscosity are determined by monitoring the liquid film thickness deposited in a microchannel based on the hydrodynamics of Taylor flow. Measurements were carried out for pure liquids and binary aqueous liquid mixtures. The results agreed well with reference data and theoretical models. This novel method has considerable potential for measuring dynamic interfacial tension of complex mixtures. Furthermore, it offers opportunity for integrating property measurement with two-phase flow in microchannel, opening new lines of applications. [ABSTRACT FROM AUTHOR]

The negative thermal expansion (NTE) behavior provides us an opportunity to design materials with controllable coefficient of thermal expansion (CTE). In this letter, we report a tunable isotropic thermal expansion in the cubic (Sc1-xZrx)F3+8 over a wide temperature and CTE range (al¼=-4.0 to+16.8*10-6 K-1, 298-648 K). The thermal expansion can be well adjusted from strong negative to zero, and finally to large positive. Intriguingly, isotropic zero thermal expansion (al¼2.6*10-7 K-1, 298-648 K) has been observed in the composition of (Sc0.8Zr0.2)F3+8. The controllable thermal expansion in (Sc1-xZrx)F3+8 is correlated to the local structural distortion. Interestingly, the ordered magnetic behavior has been found in the zero thermal expansion compound of (Sc0.8Zr0.2)F3+8 at room temperature, which presumably correlates with the unpaired electron of the lower chemical valence of Zr cation. The present study provides a useful reference to control the thermal expansion and explore the multi-functionalization for NTE materials. [ABSTRACT FROM AUTHOR]

The negative thermal expansion (NTE) behavior provides us an opportunity to design materials with controllable coefficient of thermal expansion (CTE). In this letter, we report a tunable isotropic thermal expansion in the cubic (Sc1-xZrx)F3+8 over a wide temperature and CTE range (al¼=-4.0 to+16.8*10-6 K-1, 298-648 K). The thermal expansion can be well adjusted from strong negative to zero, and finally to large positive. Intriguingly, isotropic zero thermal expansion (al¼2.6*10-7 K-1, 298-648 K) has been observed in the composition of (Sc0.8Zr0.2)F3+8. The controllable thermal expansion in (Sc1-xZrx)F3+8 is correlated to the local structural distortion. Interestingly, the ordered magnetic behavior has been found in the zero thermal expansion compound of (Sc0.8Zr0.2)F3+8 at room temperature, which presumably correlates with the unpaired electron of the lower chemical valence of Zr cation. The present study provides a useful reference to control the thermal expansion and explore the multi-functionalization for NTE materials. [ABSTRACT FROM AUTHOR]

We demonstrate that the magneto-optic-Kerr effect with normal light incidence can be used to obtain quantitative optical measurements of both components of spin-orbit-induced torque (both the antidamping and effective-field components) in heavy-metal/ferromagnet bilayers. This is achieved by analyzing the quadratic Kerr effect as well as the polar Kerr effect. The two effects can be distinguished by properly selecting the polarization of the incident light. We use this alloptical technique to determine the spin-orbit torques generated by a series of Pt/Permalloy samples, finding values in excellent agreement with spin-torque ferromagnetic resonance measurements. [ABSTRACT FROM AUTHOR]

We report a 23.4% improvement of conversion efficiency in solar cells based on InGaN/GaN multiple quantum wells by using a patterned sapphire substrate in the fabrication process. The efficiency enhancement is due to the improvement of the crystalline quality, as proven by the reduction of the threading dislocation density. More importantly, the better crystalline quality leads to a positive photovoltaic efficiency temperature coefficient up to 423 K, which shows the property and advantage of wide gap semiconductors like InGaN, signifying the potential of III-nitride based solar cells for high temperature and concentrating solar power applications. [ABSTRACT FROM AUTHOR]

The electronic structure and optical properties of the new solar cells absorber material: mixed perovskites CsSnxPb(1-x)I3 are studied by the first-principle calculations with mBJ+SOC (modified Beak Johnson approximation plus spin-orbit coupling) method. The band gap of the serial of compounds almost quasi-linearly reduces with increasing Sn content from 0.96 eV (x = 0) to 0.16 eV (x = 1). Optical absorption coefficient revealed a progressive red shift with the increment of the Sn content, accompanying with the absorption edge broadening. The absorption coefficient and Ideal Power Absorption Coefficient (IPAC) increase greatly with the Pb atoms being partially substituted by Sn atoms. The pure CsSnI3 has the highest IPAC, but it is unstable in the air because the Sn2+ will be oxidized to Sn4+. So our results indicate that partially substituted CsSnxPb(1-x)I3 might be the good solar cell absorption material. [ABSTRACT FROM AUTHOR]

The (0001¯) C face of 4H-SiC wafer was etched by reactive ion etching in SF6/O2 plasma. The effect of etching parameters, such as work pressure, SF6:O2 ratio and etching time, on the residue formation were systematically investigated. The residue morphologies were observed by scanning electron microscopy and atomic force microscopy, respectively. The residues have spike shape and their facets are defined as {11¯02¯} crystal planes. They are formed at beginning of the etching and no new spikes are generated as prolonging etching time. Both work pressure and SF6:O2 ratio play significant role in the spike formation. The residues can be eliminated completely by increasing the SF6:O2 ratio and work pressure. On the basis of experimental results and of 4H-SiC crystal structure, the spike formation model is proposed. [ABSTRACT FROM AUTHOR]

The electronic structure and optical properties of the new solar cells absorber material: mixed perovskites CsSnxPb(1-x)I3 are studied by the first-principle calculations with mBJ+SOC (modified Beak Johnson approximation plus spin-orbit coupling) method. The band gap of the serial of compounds almost quasi-linearly reduces with increasing Sn content from 0.96 eV (x = 0) to 0.16 eV (x = 1). Optical absorption coefficient revealed a progressive red shift with the increment of the Sn content, accompanying with the absorption edge broadening. The absorption coefficient and Ideal Power Absorption Coefficient (IPAC) increase greatly with the Pb atoms being partially substituted by Sn atoms. The pure CsSnI3 has the highest IPAC, but it is unstable in the air because the Sn2+ will be oxidized to Sn4+. So our results indicate that partially substituted CsSnxPb(1-x)I3 might be the good solar cell absorption material. [ABSTRACT FROM AUTHOR]

Acoustic energy transfer (AET) has been widely used for contactless energy delivery to implantable devices. However, most of the energy harvesters (ultrasonic receivers) for AET are macro-scale transducers with large volume and limited operation bandwidth. Here, we propose and investigate two microelectromechanical systems diaphragm based piezoelectric ultrasonic energy harvesters (PUEHs) as an alternative for AET. The proposed PUEHs consist of micro-scale diaphragm array with different geometric parameter design. Diaphragms in PUEH-1 have large length to width ratio to achieve broadband property, while its energy harvesting performance is compromised. Diaphragms in PUEH- 2 have smaller length to width ratio and thinner thickness to achieve both broadband property and good energy harvesting performance. Both PUEHs have miniaturized size and wide operation bandwidth that are ideally suitable to be integrated as power source for implantable biomedical devices. PUEH-1 has a merged -6 dB bandwidth of 74.5% with a central frequency of 350 kHz. PUEH-2 has two separate -6 dB bandwidth of 73.7%/30.8% with central frequencies of 285 kHz/650 kHz. They can adapt to various ultrasonic sources with different working frequency spectrum. Maximum output power is 34.3 nW and 84.3 nW for PUEH-1 and PUEH-2 at 1mW/cm2 ultrasound intensity input, respectively. The associated power density is 0.734 μW/cm2 and 4.1 μW/cm2, respectively. Better energy harvesting performance is achieved for PUEH-2 because of the optimized length to width ratio and thickness design. Both PUEHs offer more alignment flexibility with more than 40% power when they are in the range of the ultrasound transmitter. [ABSTRACT FROM AUTHOR]

The epitaxial growth of FeSi film on (001) 0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 (PMN-0.32PT) was fabricated by sputtering and confirmed by high-resolution transmission electron microscopy. A fourfold symmetric angular remanent magnetization curve of as-deposited FeSi thin film is well fitted theoretically by considering the cubic magnetocrystalline anisotropy. We found that the fourfold anisotropy decreases slightly when an electric field (E) is applied on the Pt/PMN-0.32PT/FeSi/Ta heterostructures with Pt layer as the positive electrode. However, a magnetic anisotropy transition from fourfold anisotropy to twofold anisotropy occurs under negative E. The strain-electric field curve suggests that the observed different variation trend of magnetic anisotropy results from the asymmetric strain response on the polarity of E. Moreover, once the transition happens, it was irreversible unless the heterostructures are heated above the phase transition temperature of PMN-0.32PT. [ABSTRACT FROM AUTHOR]

Planar anisotropy Nd2Co17 flakes fractured along c crystal plane were fabricated by surfactantassisted high-energy ball milling technique. The magnetic flakes have a diameter range of 5-20 µm and a typical thickness of approximately 120 nm. The frequency dependence of complex permeability of Nd2Co17 epoxy resin composite has been investigated in the frequency range of 0.1-18 GHz. The measurement results show that the natural resonance frequency reaches 12.5 GHz while the initial permeability survives up to 2.26. The superior high frequency properties come from the large out-of-plane anisotropy field and the flake structure fractured along the c crystal plane of Nd2Co17. The planar anisotropic Nd2Co17 flakes have significant potential applications in the high-frequency devices working in the frequency beyond 10 GHz. [ABSTRACT FROM AUTHOR]

The epitaxial FeSi thin films on (001) 0.7[Pb(Mg1/3Nb2/3)O3]-0.3[PbTi0.3O3] (PMN-0.3PT) substrates were fabricated by radio frequency magnetron sputtering. The observed asymmetric strain-electric field curve suggests a tensile strain switching between two perpendicular directions in PMN-0.3PT with the variation of polarity of electric fields. A simple theoretical simulation of the free energy landscape shows that the stable magnetization easy axis (MEA) of FeSi with the inherent cubic magnetocrystalline anisotropy depends on the strength and direction of an extra strain induced uniaxial anisotropy. A reversible and non-volatile 90° switching of MEA by ±6 kV/cm pulses was confirmed by the angular dependence of remanent magnetization and Kerr hysteresis loops in Ta/FeSi/PMN-0.3PT/Pt heterostructures. [ABSTRACT FROM AUTHOR]

A reaction environment modulation strategy was employed to promote the H2 production over plasmonic Au/semiconductor composites. It is shown that the fast consumption of the holes in plasmonic Au nanoparticles by methanol in alkaline reaction environment remarkably increases H2 generation rate under visible light. The photocatalytic reaction is mainly driven by the interband transition of plasmonic Au nanoparticles, and the apparent quantum efficiency of plasmon-assisted H2 production at pH 14 reaches 6% at 420 nm. The reaction environment control provides a simple and effective way for the highly efficient solar fuel production from biomass reforming through plasmonic photocatalysis in future. [ABSTRACT FROM AUTHOR]

By increasing the section thickness of a triangular flexible hinge, this study focuses on optimal selection of parameters of fillet triangle flexible hinges and flexible support. Based on Castigliano's second theorem, the flexibility expression of the fillet triangle flexible hingewas derived. Then, the case design is performed, and the comparison of three types of flexible hinges with this type of flexible hinge was carried out. The finite element models of fillet triangle flexible hinges and flexible support were built, and then the simulation results of performance parameters were calculated. Finally, the experiment platform was established to validate analysis results. The maximum error is less than 8%, which verifies the accuracy of the simulation process and equations derived; also the fundamental frequency fits the requirements of the system. The fillet triangle flexible hinge is proved to have the advantages of high precision and low flexibility. [ABSTRACT FROM AUTHOR]

Aluminum Nitride (AlN) based surface acoustic wave (SAW) pressure sensors for harsh environment applications are of great interest in recent years. Such sensor employs a thick diaphragm (~50 μm) to endure the high pressure, but this seriously limits the sensitivity of these devices. Understanding of the working mechanism and the effect of geometrical parameters will yield the design principles to achieve improved sensitivity. In this letter, the effect of diaphragm on the performance of SAW pressure sensors is studied. AlN based SAW resonators on (100) wafer with different diaphragm shapes are fabricated, packaged, and characterized. Pressure coefficient of frequency (PCF) of pressure sensors with circular diaphragm, rectangular diaphragm (small aspect ratio) and rectangular diaphragm (large aspect ratio) is found to be 0.071 ppm/psi, 0.038 ppm/psi, and 0.171 ppm/psi, respectively. The longitudinal and lateral strains along the SAW propagation direction (h100i direction) have the opposite effects on the frequency change, i.e., longitudinal strain increases the resonant frequency while lateral strain decreases the resonant frequency. Hence, the measured PCF is a combined effect of the two strains, whereby increase in lateral strain results in lower PCF. The ratio of longitudinal/lateral strain is determined by the diaphragm shape. The rectangular diaphragm (large aspect ratio) with only lateral strain thus shows negative PCF. Additionally, by changing the wafer plane, SAW propagation direction and ratio of longitudinal/lateral strains may help to enhance the primary strain effect and minimize the reverse strain effect. This approach could further improve the sensitivity of pressure sensor without sacrificing its high pressure sensing range for harsh environment applications. [ABSTRACT FROM AUTHOR]

Two-dimensional, oblique detonations induced by a wedge are simulated using the reactive Euler equations with a detailed chemical reaction model. The focus of this study is on the oblique shock-to-detonation transition in a stoichiometric hydrogenair mixture. A combustible, gas mixture at low pressure and high temperature, corresponding to the realistic, inflow conditions applied in oblique detonation wave engines, is presented in this study. At practical flight conditions, the present numerical results illustrate that oblique detonation initiation is achieved through a smooth transition from a curved shock, which differs from the abrupt transition depicted in the previous studies. The formation mechanism of this smooth transition is discussed and a quantitative analysis is carried out by defining a characteristic length for the initiation process. The dependence of the initiation length on different parameters including the wedge angle, flight Mach number, and inflow Mach number is discussed. Despite the hypothetical nature of the simulation configuration, the present numerical study uses parameters we deem relevant to practical conditions and provides important observations for which future investigations can benefit from in reaching toward a rigorous theory of the formation and self-sustenance of oblique detonation waves. [ABSTRACT FROM AUTHOR]

The dynamics of the F+H2(v=0, j=0, 1) reactions have been studied at the collision energy of 1.27 kcal/mol using a high-resolution crossed molecular beam apparatus. HF product rotational state resolved differential cross sections have been obtained at the v'=1, 2, 3 levels. The product HF(v'=2) angular distributions are predominantly backward scattered for both H2 (j=0, 1) reagents. However, the distributions of product HF(v'=2) rotational states for the F+H2(v=0, j=0) reaction are significantly different from those for the F+H2(v=0, j=1) reaction. Experimental results show that the rotational excitation of H2 produces rotationally 'hotter' HF(v'=2) product. In addition, the HF(v'=3) product is more likely scattered into the forward direction when the H2 reagent is populated at j=0 state, which could be attributed to a slow-down mechanism. [ABSTRACT FROM AUTHOR]