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The substitution of rare-earth ions has been recognized as an effective way to modify the multiferroic properties, especially to realize the electric field-controlled magnetism in BiFeO3 ceramics, in which the symmetry modulation of R3c/Pna21 and the unlocked ferromagnetism through breaking the cycloidal spin structure are the key issues. Here, the enhancement of ferroelectric polarization and weak ferromagnetism are investigated in Bi1−xLaxFeO3 ceramics together with the magnetoelectric coupling coefficient αME with the development of the Pna21 phase. The expected electric field-controlled magnetism is achieved at the phase boundary through the electric field-induced transition of Pna21/R3c, where the variation of magnetization reaches 34.18 emu/mol (58.95%) at x = 0.18 after poling. [ABSTRACT FROM AUTHOR]

Manipulation of carrier types in SnSe crystals is quite advantageous to fabricate SnSe-based homojunction devices such as thermoelectric modules. However, tuning the n-type charge carrier at an optimal level of SnSe is quite challenging because of its natural p-type without intentional doping. Here, we report the realization of the n-type SnSe through halogens or Ce doping. Importantly, heavily electron doped SnSe single crystals (∼1019 cm−3) can be obtained by Ce-doping through the Bridgeman method. The electrical conductivity of as-grown SnSe crystals evolves from thermally activated behavior to the metallic one when the electron concentrations are increased from 1016 to 1019 cm−3. Remarkably, the power-factor and electronic quality factor of heavily electron Ce-doped SnSe crystals can reach 1.59 and 0.44 μW cm−1 K−2 at 300 K, respectively, which is one of the best thermoelectric n-type SnSe. This work suggests that Ce-doping through the Bridgeman method is an ideal route for further improving the thermoelectric property of n-type SnSe crystals. [ABSTRACT FROM AUTHOR]

The aging effect and the metastable ferroelectric state are investigated in the Ba4Eu2(Ti0.9Zr0.1)4Ta6O30 ceramic, where the tetragonal tungsten bronze structure with a P4bm space group is confirmed. When the compound is cooled from temperatures far above its transition temperature (TC), a very slim polarization-electric field curve is observed at 300 K. After 3 days of aging at 300 K, an obvious increase in the remanent polarization and the coercive electric field can be obtained. Moreover, a gradual recovery of the endothermic peak is detected in the differential scanning calorimeter curves when the compound is cooled from temperatures above TC and aged at 300 K for several days. These phenomena are interpreted as the result of a metastable ferroelectric state and the related aging effect, which may be deeply concerned with the compositional inhomogeneity and the hindered superstructure transformation. Through manipulating A and B site cation substitutions, the range of the metastable ferroelectric state can be tuned, and compounds with a different ferroelectric transition process can be obtained. [ABSTRACT FROM AUTHOR]

Lead-free relaxors Ba5RSn3Nb7O30 (R = La, Nd, Sm) with a tetragonal tungsten bronze structure were prepared by a standard solid-state reaction process, and the dielectric and ferroelectric properties were systematically determined together with the structures and microstructures. Rietveld refinement results suggested that a single-phase tungsten bronze structure in space group P4/mbm was obtained for all the compositions. Both the dielectric constant (ε′) and the dielectric loss (tan δ) exhibited a broad maximum with evident frequency dispersion far below room temperature, which indicated the typical relaxor nature. The selected area electron diffraction patterns revealed that the relaxor behavior in the present system originated from the incommensurate structure modulation. The dark-field transmission electron microscopy images confirmed the presence of polar nanoregions in the areas generating the satellite reflections of incommensurate structure modulation, which implied a possible correlation between the incommensurate structure modulation and polar nanoregions in tungsten bronze relaxors. [ABSTRACT FROM AUTHOR]

Effects of B site ions on the relaxor to normal ferroelectric crossover in Ba4Sm2Zr4(NbxTa1-x)6O30 (x = 0, 0.3, 0.5, 0.7, 0.9, and 1) tungsten bronze ceramics were investigated. The tetragonal tungsten bronze structure in space group P4/mbm was confirmed for compositions of x =0, 0.3, and 0.5, while space group P4bm was confirmed for compositions of x =0.7, 0.9, and 1. With the increasing Nb content in the B site, the dielectric properties showed a crossover from the relaxor to normal ferroelectric behavior, accompanied with the disappearance of frequency dispersion, increased ferroelectric transition temperature, and larger dielectric constant value. The room temperature Raman spectra for compositions of x =0 and x =1 showed different vibration modes of the oxygen octahedral, and the temperature dependence of the integrated intensity of Raman bands indicated the different structural transition process. Unlike the effects of A site ions, the onset of the relaxor/normal ferroelectric behavior of Ba4Sm2Zr4(NbxTa1-x)6O30 was mainly caused by the different electron configuration of Nb and Ta. [ABSTRACT FROM AUTHOR]

Electrically controlled band gap and topological electronic states are important for the nextgeneration topological quantum devices. In this letter, we study the electric field control of band gap and topological phase transitions in multilayer germanane. We find that although the monolayer and multilayer germananes are normal insulators, a vertical electric field can significantly reduce the band gap of multilayer germananes owing to the giant Stark effect. The decrease of band gap eventually leads to band inversion, transforming them into topological insulators with nontrivial Z2 invariant. The electrically controlled topological phase transition in multilayer germananes provides a potential route to manipulate topologically protected edge states and design topological quantum devices. This strategy should be generally applicable to a broad range of materials, including other twodimensional materials and ultrathin films with controlled growth. [ABSTRACT FROM AUTHOR]

Ferroelectricity and polarization reversal dynamics in Ba4Sm2Ti4Ta6O30 tungsten bronze ceramics were investigated by measuring dielectric spectra and the evolution of hysteresis loops over a wide temperature range. With decreasing temperature, the dielectric properties and differential scanning calorimetry results showed diffuse peaks at ~280 K with large thermal hysteresis, suggesting a first order ferroelectric transition. A dielectric relaxation was observed at low temperature that followed the Vogel-Fulcher relationship. The saturation and remanent polarizations of the Ba4Sm2Ti4Ta6O30 ceramics showed remarkable dependence on the applied field and temperature. The temperature dependence of the coercive field was divided into three linear regions and fitted to the Vopsaroiu model. Activation energies for polarization reversal of 0.73, 0.79, and 0.65 eV were determined for the following three regions: (I) the diffuse ferroelectric transition region (323.15-293.15 K), (II) the region just below the ferroelectric transition temperature (293.15-233.15 K), and (III) the low temperature relaxation region (233.15-173.15 K), respectively. The decrease of the activation energy in region III was attributed to the low temperature relaxation of Ba4Sm2Ti4Ta6O30. [ABSTRACT FROM AUTHOR]

Any of two or more two-dimensional (2D) materials with similar properties can be alloyed into a new layered material, namely, 2D alloy. Individual monolayer in 2D alloys is kept together by van der Waals interactions. The property of multilayer alloys is a function of their layer number. Here, we studied the shear (C) and layer-breathing (LB) modes of Mo0.5W0.5S2 alloy flakes and their link to the layer number. The study reveals that the disorder effect is absent in the C and LB modes of 2D alloys, and the monatomic chain model can be used to estimate the frequencies of the C and LB modes. We demonstrated how to use the frequencies of C and LB modes to identify the layer number of alloy flakes deposited on different substrates. This technique is independent of the substrate, stoichiometry, monolayer thickness, and complex refractive index of 2D materials, offering a robust and substrate-free approach for layer-number identification of ultrathin flakes of 2D materials, such as 2D crystals and 2D alloys. [ABSTRACT FROM AUTHOR]

We propose and model a terahertz detector based on the transport properties of an excited carrier population in a nanopore structure. The present work supports the proposal with detailed electronic dispersion, optical absorption, and carrier transport. [ABSTRACT FROM AUTHOR]

Rare earth ion (RE)-substitution has been recognized as an effective way for improving multiferroic properties especially for realizing the electric field-controlled magnetism in BiFeO3 ceramics, where the symmetry modulation of R3c-Pna21-Pbnm and unlocking ferromagnetism by destroying the cycloidal spin structure are the key points. In Lu-substituted BiFeO3 ceramics, however, the Pna21 phase is not involved. In the present work, La/Lu co-substitution was investigated to involve the Pna21 phase in BiFeO3 ceramics. The phase transition from R3c to Pna21 occurred with an increase in x, and the mixed structure of R3c, Pna21, and Pbnm phases was determined in Bi0.82−xLaxLu0.18FeO3 ceramics. The greatly enhanced ferroelectric polarization and the switching from antiferromagnetic to the weak ferromagnetic state through the destruction of the cycloidal spin structure were achieved. Subsequently, the direct magnetoelectric coupling coefficient αME up to 2.02 mV/cm Oe was obtained. The increased effective ionic radius of RE in the present ceramics played a key role in involving Pna21 phase in RE-substituted BiFeO3 ceramics, and the critical value was about 0.104 23(2) nm. [ABSTRACT FROM AUTHOR]

A phosphorescent (Ph) cyclometallated rhenium (I) (ReI) complex was synthesized by reacting 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline with pentacarbonylbromorhenium in refluxing toluene solutions. The precipitates were easily sublimed to obtain a pure electrically neutral carbonyl diamine ReI complex, (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline)Re(CO)3Br. The Re complex was used as an orange emitting dopant in 4,4′-N,N′-dicarbazole-biphenyl host to fabricate Ph organic light-emitting diodes (PhOLEDs). The maximum electroluminescence (EL) efficiency and luminance of 21.8 cd/A and 8315 cd/cm2 were harvested, respectively, which were the highest EL results among the PhOLEDs based on ReI complexes. The improvements of the EL performances could be ascribed to the synergistic effects of together incorporation of two reciprocally repulsive phenyl and methyl groups on the backbone of 1,10-phenanthroline molecule of the ligand. [ABSTRACT FROM AUTHOR]

The authors show that a current flowing in a direction not perpendicular to the layer planes of an exchange-biased spin valve systematically changes the exchange bias. The direction of the exchange bias can be completely reversed when a large enough current is applied. This effect occurs only when the direction of the initial sweeping magnetic field is antiparallel to the exchange-bias field. The effect is attributed to the recently predicted current-induced torque in an antiferromagnet and provides evidence to support the prediction that the critical current is smaller in an antiferromagnet than the typical value for current switching in a ferromagnet. [ABSTRACT FROM AUTHOR]

The authors report an experiment in which optical pulses are effectively stored via maximal atomic coherence in a three-level Λ-type 87Rb atomic system, and then selectively released at one of the two different wavelengths by turning on the retrieve control pulse at 794.9842 or 794.9698 nm. The storage time up to 360 ns was demonstrated. [ABSTRACT FROM AUTHOR]

Dielectric relaxation and ultrasonic attenuation spectra of Sr4La2Ti4Nb6O30 tungsten bronze ceramics were investigated over a broad temperature range. A broad permittivity peak with strong frequency dispersion was observed around 200 K, which followed well the Vogel-Fulcher relationship, and is attributed to relaxor ferroelectric behavior with spin glass nature. The ultrasonic investigation provided further evidence on this thermally activated process, and both the dielectric relaxation and the freezing of polar clusters were clearly observed in the ultrasonic velocity shift and ultrasonic attenuation spectra. [ABSTRACT FROM AUTHOR]

The exciton properties play a crucial role in controlling the optical properties of molybdenum disulfide (MoS2). In this work, horizontally oriented MoS2 (H-MoS2), horizontally and vertically oriented MoS2 (HV-MoS2), and vertically oriented MoS2 (V-MoS2) on the same SiO2/Si substrate have been synthesized and investigated using temperature-dependent photoluminescence spectroscopy from 7 to 300 K. Except for direct excitons called as A and B peaks, indirect exciton named as I peak is discovered with the splitting of three peaks. Compared with direct excitons, indirect excitons appear to be more susceptible to the orientation of MoS2. The exciton activation energies are larger, and the exciton–phonon coupling is stronger in V-MoS2 than in H-MoS2. The exciton properties of HV-MoS2 are more similar to those of V-MoS2, but there are some unusual phenomena. Our work provides a reference for optoelectronic applications based on transition-metal dichalcogenides represented by MoS2 grown with horizontal and vertical orientations. [ABSTRACT FROM AUTHOR]

In this study, the structure evidence of the Pna21 phase and the field-induced transition of Pna21/R3c have been quantitatively investigated in Bi1-xSmxFe0.99Ti0.01O3 (x = 0.12, 0.14, and 0.16) ceramics together with the subsequent electric field-controlled magnetism. A sequential phase transition of R3c-Pna21-Pbnm is detected by Rietveld refinement of the x-ray diffraction data. Further, the electric field-induced phase transition is investigated near the morphotropic phase boundary at x = 0.14, where the structure is tuned from Pna21 to R3c with poling treatment, and this transition could become reversible with as-annealing after poling. For x = 0.14, the structure is tuned from Pna21 to R3c with poling treatment, and this transition could become reversible with as-annealing after poling. The phase transition is confirmed by Rietveld refinements together with VSM measurements, providing an opportunity for electric field-controlled magnetism. The magnetoelectric coupling is enhanced, and the linear magnetoelectric coefficient αME up to 0.91 mV/Oe·cm is obtained in Bi1-xSmxFe0.99Ti0.01O3 ceramics. More importantly, the R3c and Pna21 structures are confirmed by selected area electron diffraction and dark-field analysis at x = 0.14, and the high-resolution TEM image demonstrates the coexistence of the R3c and Pna21 structures. [ABSTRACT FROM AUTHOR]

The crossover from normal to relaxor ferroelectrics in Sr0.25Ba0.75(Nb1−xTax)2O6 (x = 0, 0.1, 0.25, and 0.5) ceramics was determined together with the structure evolution. A single-phase tungsten bronze structure in space group P4bm (x = 0 and 0.1) or P4/mbm (x = 0.25 and 0.5) was obtained in the entire composition range. The lattice parameter a increased, while c, tetragonality c/a, and cell volume decreased with increasing x. Meanwhile, the dielectric maximum temperature Tm went down and the dielectric peak exhibited an enhanced diffused nature with a stronger frequency dispersion, where the saturated P–E loop (x = 0 and 0.1) transformed to a slim relaxor loop (x = 0.25) and finally to the linear one (x = 0.5). Raman spectra results revealed the reduced covalence between the B-site cation and the oxygen ion as a result of Ta-substitution. The coexistence of Nb5+ and Ta5+, which possessed the distinct covalence with the oxygen ion, played the key role in the structural variation and crossover from normal to relaxor ferroelectrics in the present system. [ABSTRACT FROM AUTHOR]

Thermoelectric materials, based on photo-thermoelectric effect (PTE), may be promising in photo-detection because of their self-power, extremely broad-band, and free of cryogenic attachments. Up to now, the performance of PTE is mainly optimized through enhancement of extrinsic absorption such as using optical metamaterials. Instead, we here improve the PTE through materials engineering, accordingly systematically investigated the PTE of both P- and N-type SnSe crystals with different carrier concentrations (1017–1019 cm−3). P-type SnSe has much better photo-thermoelectric performance than the N-type one. Among P-type SnSe, the SnSe crystal with the largest carrier concentration (∼1019 cm−3 at room temperature) demonstrates the highest photo-thermoelectric performance. Analysis by a modified two-temperature model suggests that the key parameter of enhanced PTE is the high electrical conductivity, which leads to large optical absorption and large temperature difference. Our work provides a guideline on how to engineer thermoelectric materials to enhance their photo-thermoelectric performance. [ABSTRACT FROM AUTHOR]

This Letter reports two kinds of oxygen-containing plasma treated β-Ga2O3 Schottky barrier diodes (SBDs), including N2O plasma treatment and O2 plasma treatment, and the SBD without plasma is prepared for comparison. I–V characteristics, breakdown characteristics, and trap state characteristics of three devices have been studied. It is found that the turn-on voltage of SBDs with N2O plasma can reduce to 0.6 V, and the better current density of 750 A/cm2 and an on-resistance of 3.5 mΩ cm2 are obtained after the N2O plasma treatment. Moreover, the breakdown voltage of SBDs with N2O plasma is 50.2% higher than the conventional one, whose value reaches 323 V. In addition, the trap states' characteristics of the devices are studied, which show that the oxygen-containing plasma can reduce the deep level trap states density partly in the anode region, which can improve the surface quality effectively. [ABSTRACT FROM AUTHOR]

A β-Ga2O3 Schottky barrier diode (SBD) with a p-type NiOx guard ring was fabricated, and the reverse leakage and subthreshold leakage current reduction was found at high temperatures from temperature-dependent I–V characteristics. The functional mechanisms of NiOx as edge termination on leakage reduction were studied. NiOx can increase the barrier height and passivate the defects at the interface, resulting in the suppression of subthreshold leakage and elimination of current crowding effect confirmed by a thermal emission microscope. From the temperature-dependent x-ray photoelectron spectroscopy characteristics, more holes generated to deplete Ga2O3 at higher temperatures were found. It leads to reduce the reverse leakage current. The small-polaron transportation in NiOx is proposed to argue the implausibility of the leakage conduction in NiOx. This work will offer critical physical insight and a valuable route for developing low-leakage Ga2O3 SBDs. [ABSTRACT FROM AUTHOR]

Recently, the extremely large magnetoresistance (MR) observed in transition metal telluride, like WTe2, attracted much attention because of the potential applications in magnetic sensor. Here, we report the observation of extremely large magnetoresistance as 3.0x104% measured at 2K and 9 T magnetic field aligned along [001]-ZrSiS. The significant magnetoresistance change (~1.4x104%) can be obtained when the magnetic field is titled from [001] to [011]-ZrSiS. These abnormal magnetoresistance behaviors in ZrSiS can be understood by electron-hole compensation and the open orbital of Fermi surface. Because of these superior MR properties, ZrSiS may be used in the magnetic sensors. [ABSTRACT FROM AUTHOR]

ZnMnO films codoped with Ga, Cr, and Fe were deposited on sapphire substrates via pulsed laser deposition. The structures, magnetization, and transport properties of p-type ZnMnO films can be tuned using n-type Ga, Cr, and Fe codopants. The Coulombic attraction between n- and p-type dopants favorably decreases the energy of system, thereby preventing dopant aggregation and effectively enhancing dopant solubility. The above noncompensated n-p codoping can provide a certain amount of carrier density and local spins and results in the room temperature magnetizations and low temperature positive or negative magnetoresistances in ZnO wide gap semiconductors. [ABSTRACT FROM AUTHOR]

Effects of Ca-substitution on the crystal structure and dielectric properties were investigated for Ba5SmTi3Nb7O30 tungsten bronze ceramics. The tetragonal tungsten bronze structure in space group P4bm was determined in Ba4CaSmTi3Nb7O30 ceramics, which was the same for Ba5SmTi3Nb7O30. The c-axis off center displacement in both B1 and B2-sites for Ba5SmTi3Nb7O30 was slightly larger than that in BaCaSmTi3Nb7O30, while the distortion of Ti/Nb(2)O6 octahedra in Ba4CaSmTi3Nb7O30 was obviously suppressed compared with that in Ba5SmTi3Nb7O30. Though there were also two dielectric anomalies observed in Ba4CaSmTi3Nb7O30, the relaxor ferroelectric nature was changed to the normal ferroelectric one, and both the endothermal peak in differential scanning calorimetry curve and the significant thermal hysteresis of the phase transition confirmed the first order ferroelectric transition. These results indicated that the ferroelectric nature of Ba4CaSmTi3Nb7O30 was more close to that in Ba4Sm2Ti4Nb6O30, and it could be concluded that the ferroelectric nature in filled tungsten bronze ceramics was primarily dominated by the A-site occupation rather than B-site occupation. [ABSTRACT FROM AUTHOR]

We have designed and fabricated a half-wavelength reflection line resonator that consists of a pair of coupled microstrip lines on a GaAs/AlGaAs heterostructure. By changing the top gate voltage on a small square with a two-dimensional electron gas under the resonator, the quality factor was tuned over a large range from 2700 to below 600. Apart from being of fundamental interest, this gate modulation technique has the potential for use in on-chip resonator applications. [ABSTRACT FROM AUTHOR]

Inverse photoemission spectroscopy (IPES) enables the characterization of the density of states of unoccupied energy states above the Fermi level. However, due to the relatively high electron currents required to achieve useful signal to noise ratios, sample damage is a concern. Regioregular poly(3-hexylthiophene) (rr-P3HT) was used to systematically study the influence of electron radiation during IPES measurements on a prototypical conductive polymer. A series of IPES measurements exposing the samples to a range of electron fluxes was performed. An analysis of the electronic structure and the morphology showed that significant changes occurred in the investigated samples depending on the electron flux. X-ray diffraction results revealed that the root cause of the spectral changes is most likely related to crystallization of the film in an edge-on orientation. This was confirmed by Raman spectroscopy where both the C-C and C=C stretch modes shifted to lower frequencies after 5 IPES scans indicating a more ordered molecular structure. The observation of these stretch modes even after exposure to higher electron flux indicates that the main chemical structure of the P3HT molecules remains mostly intact during the IPES measurements. The absence of significant changes in C 1s and S 2p photoemission core level lines also confirmed this conclusion. [ABSTRACT FROM AUTHOR]

A low temperature controlled annealing technique was utilized to improve the performance of vertical β-gallium oxide (β-Ga2O3) Schottky barrier diodes (SBDs) in this work. The nickel is diffused into Ga2O3, and NiO was formed at the interface between the anode and semiconductor generating p–n junction after low temperature annealing. Simultaneously, the trap state density of interface Ni/Ga2O3 as well as the carbon bonded with oxygen on the surface was reduced, which was proved by the capacitance and conductance measurements and x-ray photoelectron spectroscopic analysis, respectively. Combined the decreased saturation current density by three orders of magnitude from 1.21 × 10−6 to 9.27 × 10−8 and 5.12 × 10−9 A/cm2 and larger breakdown voltage from 220 to 270 V owing to the optimized interface and the formation of NiO, a low temperature annealing technique makes certain effective improvement for vertical β-Ga2O3 SBDs via interface engineering. [ABSTRACT FROM AUTHOR]

Hybrid improper ferroelectricity (HIF) has received increasing scientific attention since it provides great potential for realizing single phase room temperature multiferroicity with strong magnetoelectric coupling, and Ruddlesden–Popper (R–P) compounds AO(ABO3)n with even n are the most important candidates for HIFs. However, the modulation of ferroelectric polarization is recognized as a challenging issue. Here, Sr3−xBaxSn2O7 ceramics with a large remanent polarization with respect to other R–P HIFs (∼1.0 μC/cm2) combined with a reduced coercive field are reported. The polarization increases obviously with the increasing tolerance factor, inconsistent with the previous understanding. This is because the amplitude of tilt increases and rotation decreases, which results in the increased distortion of SnO6 octahedra. That is, the polarization of R–P compounds should be determined by the combined effects of tilting and rotation and not be simply evaluated by the tolerance factor. [ABSTRACT FROM AUTHOR]

High-performance biodegradable transient resistive random-access memories (RRAMs) with the structure of Mg/MoO3/MgO/MoO3/Mg have been fabricated on a polylactic acid (PLA) substrate. Without the electroforming process, the devices have high ratios of the high-resistance state (HRS)/low-resistance state (LRS) (>50% of devices reaching above 106 and ∼3% reaching above 1011), good retention properties (both the HRS and LRS without deterioration within 2 × 104 s), and good endurance properties (continuously switched between the HRS and LRS >100 times under appropriate voltage pulses). By investigating the effect of different top electrode (TE) and bottom electrode (BE) combinations (TE/BE: Mg/Mg, Pt/Mg, Mg/Pt, and Mg/Au) and different oxygen contents of MoO3 on the performance of devices, the resistive switching mechanism is revealed to be the redox of the Mg TE at the interface of Mg/MoO3. The HRS is attributed to the formation of MgO after Mg is oxidized by mobile oxygen ions or oxygen captured from adjacent MoO3 under applied voltage, while the LRS is ascribed to the dissolution of formed MgO. The fitting results of the measured data indicate that the conduction of the HRS is dominated by the Poole-Frenkel (P-F) emission and that of the LRS is governed by the Ohmic conduction. Moreover, the devices can degrade quickly in 0.9% NaCl solution within 5 h, except for the PLA substrate that is able to degrade in the human body. [ABSTRACT FROM AUTHOR]

The intrinsically low thermal conductivity is fundamentally important for the development of high-performance thermoelectric and thermal insulating materials. Here, we observed ultra-low cross-plane thermal conductivities of naturally misfit layered single crystals Bi2[AE]2Co2Oy (AE=Ca, Ca0.5Sr0.5, Sr, and Ba) using the time-domain thermoreflectance method. These low values are comparable to the lowest conductivity in crystalline oxides and approaching the theoretical conductivity minimum of disordered crystals. Besides, these samples show the amorphous-like temperature dependence at cryogenic temperatures and the effective mean free paths are in the same magnitudes as the lattice constants. [ABSTRACT FROM AUTHOR]

Recently, transition metal dichalcogenide (TMD) materials have shown promise in electronics and optoelectronics applications. Most of their properties are closely related to their abundant structural phases and phase transitions. For more practical applications in the future, it is necessary to tune the phase transitions in this material system. Here, we demonstrate the modulation of phase transitions in miscible WxMo1-xTe2 samples by appropriate alloying. The temperature dependent thermal conductivity along the c-axis, which strongly relates to the phase structures and the defect level, has been measured using the time-domain thermoreflectance method. In addition, a tunable hysteretic effect, induced by phase transitions, is observed in both thermal and electrical transport properties and confirmed by the consistent hysteresis in the Raman spectroscopic study. This hysteretic effect can be applied to realize phase-change storage devices. Furthermore, we provide a phase diagram to illustrate the composition dependent phase transition in WxMo1-xTe2. This work demonstrates an approach to modulate phase transition and thermal hysteresis in such a TMD material system by alloying engineering. [ABSTRACT FROM AUTHOR]

Flow-induced voltage generation on graphene has attracted great attention, but harvesting voltage by ionic liquid continuously flowing along graphene at macro-scale is still a challenge. In this work, we design a network structure of graphene grids (GG) woven by crisscrossed graphene micron-ribbons. The structure is effective in splitting the continuous fluid into "droplets" to generate consistent voltage using the mechanism of electrochemical energy generation. Key parameters such as flow rate, mesh number of GG, and slope angle are optimized to obtain maximum voltage in energy generation. The results suggest great potential of this graphene-based generator for future applications in energy harvesting. [ABSTRACT FROM AUTHOR]

We synthesis uniform Au-CdS core-shell hetero-nanorods and demonstrate the effective plasmon-exciton interaction induced optical nonlinear enhancement in metal-semiconductor hetero-nanostructures. After growing CdS semiconductor shell onto the Au nanorods, the longitudinal plasmon resonance exhibits considerable red-shift with enlarged absorption intensity. Nonlinear absorption responses transform from saturable absorption to reverse saturable absorption, and effective nonlinear absorption coefficient β is increased from -7.7 to +22.2 cm/GW. The observed behaviors indicate strong plasmon-exciton interaction and great local field enhancement. [ABSTRACT FROM AUTHOR]

We measured the radio-frequency reflection spectrum of an on-chip reflection line resonator coupled to a graphene double quantum dot (DQD), which was etched almost isolated from the reservoir and reached the low tunnel rate region. The charge stability diagram of DQD was investigated via dispersive phase and magnitude shift of the resonator with a high quality factor. Its complex admittance and low tunnel rate to the reservoir was also determined from the reflected signal of the on-chip resonator. Our method may provide a non-invasive and sensitive way of charge state readout in isolated quantum dots. [ABSTRACT FROM AUTHOR]

The authors demonstrate high response organic ultraviolet (UV) photodetector (PD) using 4,4′,4″-tri-(2-methylphenyl phenylamino) triphenylaine (m-MTDATA) and tris-(8-hydroxyquinoline) gallium (Gaq3) to act as the electron donor and acceptor, respectively. The m-MTDATA:Gaq3 blend device shows a photocurrent of 405 μA/cm-2 at -8 V, corresponding to a response of 338 mA/W under an illumination of 365 nm UV light with an intensity of 1.2 mW/cm2. The high response is attributed to the enhanced dissociation of geminate hole-electron pairs in the distributed heterojunction of the blend and suppression of radiative decay. Photophysics of the PD involved is also discussed in terms of the performance and device structures. [ABSTRACT FROM AUTHOR]

We investigated the sensitized effect of fac-tris(2-phenylpyridine) iridium [Ir(ppy)3] on tris-(dibenzoylmethanato)-mono-(bathophenanthroline) erbium (Er-DB) for 1.5 μm near-infrared emission. Compared with the neat Er-DB film, the blend film composed of Er-DB and Ir(ppy)3 with a 1:1 of the weight ratio shows 20 times and 4 times enhancement on intensity of photoluminescence (PL) and electroluminescence (EL), respectively. The improvement in both PL and EL intensities was conjectured to be the result of the energy transfer from Ir(ppy)3 to Er-DB complex, and the detailed mechanisms of the enhancement were also discussed. [ABSTRACT FROM AUTHOR]