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The resistive switching evolution of NiO/AlO in Pt/NiO/AlO/n-Si structure was investigated with postannealing time. When increasing the postannealing time, larger voltage/current is needed to turn on/turn off the structure, respectively. Large memory resistance window can be obtained by the interface modulation of NiO/AlO. For the fresh structure, the low resistance state (LRS) obeys Ohmic conduction mechanism and the high resistance state (HRS) fits Poole-Frenkel-like behavior. With the postannealing time increase, the reaction between NiO and AlO occurs. Finally, the Pt/Ni-Al-O/n-Si structure forms. Schottky emission mechanism has dominated in the HRS, while the LRS shows Poole-Frenkel-like behavior. [ABSTRACT FROM AUTHOR]

The stability, the electronic and the magnetic properties of the hydrogen-terminated zigzag graphitic C3N4 nanoribbons (ZCNNRs) were investigated by using first-principles computations. The semiconductor to half-metal transition could be realized by controlling the hydrogen content of the environment, which is independent of nanoribbon width. The semiconducting ZCNNRs are stable at low hydrogen pressure, while the ZCNNRs are half-metallic at high hydrogen concentration. The hydrogenation acts as the electron doping at high concentration, which significantly alters the electronic and magnetic properties of ZCNNRs. The transition metal-free magnetism in ZCNNRs endows them many applications in novel integrated functional nanoelectronic devices, especially spintronics. [ABSTRACT FROM AUTHOR]

Fully transparent indium–tin-oxide/high-k-rare-earth-oxide Eu2O3/F-doped SnO2 devices that show stable bipolar resistance switching have been successfully fabricated. In addition to the transmittance of above 86% for visible light, high resistance ratio, good data retention and initial forming-free resistance switching behaviour were obtained in the transparent memory. The results of high-resolution spectroscopy and x-ray photoelectron spectroscopy analyses combining with the temperature dependence of resistance suggest that metallic Eu filaments are formed in the low-resistance state. Mechanism analysis indicates that the coexistence of oxygen vacancies and metallic Eu in the Eu2O3 films plays an important role in the forming-free resistive switching performance. The switching mechanism was attributed to formation/oxidation of filamentary and oxygen ion migration. [ABSTRACT FROM AUTHOR]

Amorphous films Zr0.8Si0.2O2 were deposited on quartz substrates at room temperature, by using pulsed laser deposition technique. After annealing at high temperature, Zr0.8Si0.2O2 films suffer a phase separation to precipitate tetragonal ZrO2 nanocrystals in ZrSiO4 amorphous matrix. Their crystal structure, microstructure, optical absorbance and photoluminescence have been systematically investigated. Tetragonal ZrO2 nanocrystals show intense UV emission around 392 nm under photonic excitation with a wavelength of 250 nm. The corresponding models of electronic excitation and transition related to UV emission also have been proposed. [ABSTRACT FROM AUTHOR]

(ZrO2) x (SiO2)1− x (Zr-Si-O) films with different compositions were deposited on p-Si(100) substrates by using pulsed laser deposition technique. X-ray photoelectron spectra (XPS) showed that these films remained amorphous after annealing at 800°C with RTA process in N2 for 60 s. The XPS spectra indicated that Zr-Si-O films with x=0.5 suffered no obvious phase separation after annealing at 800°C, and no interface layer was formed between Zr-Si-O film and Si substrate. While Zr-Si-O films with x >0.5 suffered phase separation to precipitate ZrO2 after annealing under the same condition, and SiO2 was formed at the interface. To get a good interface between Zr-Si-O films and Si substrate, Zr-Si-O films with bi-layer structure (ZrO2)0.7(SiO2)0.3/(ZrO2)0.5(SiO2)0.5/Si was deposited. The electrical properties showed that the bi-layer Zr-Si-O film is of the lowest equivalent oxide thickness and good interface with Si substrate. [ABSTRACT FROM AUTHOR]

Ba1-xSrxTiO3 (BST) thin films with compositional bilayer structure are fabricated using rf magnetron sputtering by controlling the deposition conditions. A highly (100) preferred orientation is developed, and enhanced tunability is obtained with the introduction of the bilayer structure. The orientation of the films and the interface between the two layers are both responsible for the improvement in the performance. It is also demonstrated that the in situ annealing before the deposition of the upper layer plays an important role in determining the tunable properties. A long post-annealing could destroy the bilayer structure, and hence degrade the enhanced dielectric characteristics and tuning properties of the films. [ABSTRACT FROM AUTHOR]

A charge trapping memory device using Ti0.2Al0.8Ox film as charge trapping layer and amorphous Al2O3 as the tunneling and blocking layers was fabricated for nonvolatile memory application. TiAl2O5 nanocrystals are precipitated from the phase separation of Ti0.2Al0.8Ox film annealed at 900 °C. A memory window of 2.3 V and a stored electron density of 1×1013/cm2 were obtained. Good retention characteristics of the memory device at 80 °C were observed due to the deep charge trapping level as identified by the valence band offsets and electron energy loss spectrum measurements. [ABSTRACT FROM AUTHOR]

The microstructural evolution and resistive switching of glassy Ag30Ge17Se53 electrolyte films clipped by Ag active electrode, at which a positive bias was applied, and Pt inert electrode, were investigated by transmission electron microscopy observations and I-V measurements as functions of the period of electrical field treatment. It is revealed that an electrical field induced precipitation reaction forming conductive particles with orthorhombic Ag2Se structure and followed growth and networking of these particles, leading to an electrical percolation, are responsible for the transition from high resistive to high conductive state of the system. The kinetics of the precipitation reaction was also analyzed. [ABSTRACT FROM AUTHOR]

An organic bistable device with a structure Cu/Cu2S/copperphthalocyanine (Cu-Pc)/Pt was fabricated. Compared to the single layer organic device composed of Cu/Cu-Pc/Pt, the bilayer devices were observed to show distinct bistability with the resistance ratio of the off/on states up to 107 and low switch voltage (0.75–0.85 V). At least 105 switching cycles were achieved in the “write-read-erase-read” cycle voltage. The filament mechanism for the device is supported by the “metallic” behavior in their temperature dependence of the resistance in the on state. Such a memory device provides a promising structure for the nonvolatile memory. [ABSTRACT FROM AUTHOR]

The tunable property and thermal stability of (Ba0.25Pb0.25)Sr0.5TiO3 films derived by pulsed laser deposition have been investigated. The substitution of Pb for Ba in (Ba,Sr)TiO3 (BST) system has been revealed to raise the transition temperature close to room temperature (RT) and enhance the tuning property. It is proposed that nanopolar regions would occur in the films in the paraelectric state at RT, arising from the addition of Pb2+ into the A site of pervoskite structure of BST. This induces the relaxor behavior and diffuse phase transition. Hence, low temperature-dependent tunability is obtained due to the broadening of dielectric constant peak. These results demonstrated that Pb substitution could be a simple and effective method to obtain high tunability and good temperature stability simultaneously. [ABSTRACT FROM AUTHOR]

The growth of large‐scale films forms the cornerstone for future integrated photodetection applications of 2D materials. However, there is still an unwelcome trade‐off between the size of these films and the performances of devices fabricated using them. To deal with this issue, a possible scheme for film assembly is proposed using high‐quality nanolayers to achieve both outstanding device performance and large film area. Specifically, photodetectors are fabricated on nanostructured BiI3 films (1 × 1 cm2) assembled with interlaced, vertically grown 2D nanoplates. These devices inherent the excellent photodetecting capability of single‐BiI3‐nanoplate‐based photodetectors, showing responsivity of up to 2.22 AW−1, high speed photoresponse of 2 ms/5.3 ms for rise/decay times, and outstanding specific detectivity as high as 1.65 × 1012 Jones. This suggest that this approach to preparing large‐scale 2D BiI3 films holds potential for the realization of integrated high‐performance photosensing devices. Furthermore, it is anticipated that it can be to other 2D materials. [ABSTRACT FROM AUTHOR]

High‐performance bottom‐gate nonvolatile organic field‐effect transistor (OFET) devices based on a special matching energy‐band alignment between the organic semiconductor pentacene and the charge‐trapping dielectric ZnTe are reported. The lower potential difference between the conduction band minimum of ZnTe and the lowest unoccupied molecular orbital of pentacene with a weak electron conductivity endows the OFET a memory window of 10 V at an applied sweeping gate‐voltage of ±15 V, a high ION/IOFF ratio of more than 106, and good retention with a high ION/IOFF ratio of 6 × 105 after 104 s. The large memory window of the OFET is attributed to the unique energy‐band alignment of the memory device and the high density of traps in Te‐deficient ZnTe film, and the prominent retention is attributed to the deeply trapped electrons in the potential well formed by Al2O3 tunneling and blocking layers. [ABSTRACT FROM AUTHOR]

This work presents an experiment-informed, semi-empirical, elasto-plastic bond model for the discrete element modeling of woody biomass particles. The model renders nonlinear plastic deformation of materials when subjected to compression/tension, bending, and twisting, essential for accurately simulating the behavior of biomass in comminution. The model is implemented in an open-source DEM package LIGGGHTS and is assessed in a number of verification tests. The model is applied to simulate the fracturing test of notched loblolly pine blocks. Reduced bond strength is prescribed to the weak planes along the growth rings. It is found that the square-root formulation for describing the elasto-plastic normal bond contact delivers the best agreement with the experimental data over its linear and quadratic counterparts. Furthermore, the model predicts a strong anisotropic behavior of wood blocks with regard to the grain orientations, indicating that the cutting angle should be an important attribute for the optimization of biomass comminution. [Display omitted] • An experiment-informed, semi-empirical, nonlinear elasto-plastic bond model proposed • Model is capable of simulating irregular particle shapes via the bonded-sphere approach. • Model is applied to fracturing test simulation of loblolly pine wood blocks. • Material nonlinearity and anisotropy due to growth ring are captured. • The square-root form of proposed bond model delivers the best performance. [ABSTRACT FROM AUTHOR]

In this work, we present light-controlled resistive switches with p-Si/HfO2/Pt structures, in which the resistance can be controlled by a combination of electrical pulses and light. The devices have a large switching ratio (over 104) and good uniformity. Connecting two devices with a conventional resistor enables one to implement light-controlled material implication (IMP). Based on the light-controlled IMP logic, light-controlled NAND and light-controlled OR logic operations were also executed in the same devices. [ABSTRACT FROM AUTHOR]

By first-principles calculations, the magnetism of hole doped tin dichalcogenides SnX2 (X = S, Se) monolayers is systematically studied. It is found that a phase transition from nonmagnetic to ferromagnetic ground state appears once above the critical hole density (~1014 cm−2). The spin magnetic moment can maintain a magnitude of 1.0 μB/hole with excellent stability of ferromagnetic state. Furthermore, we demonstrate that strain is very useful to modulate the DOS near the valence band, resulting in the reduction of the critical hole density to ~1013 cm−2 when the strain reaches 4% (6%) in SnS2 (SnSe2), which can be realized in common field effect transistors. Moreover, the phonon dispersion calculations for the strained SnX2 monolayers indicate that they can keep the dynamical stability under the hole doping. Therefore, the strain tunable magnetic transition in hole doped tin dichalcogenides indicates their potential promising applications in spintronic devices. [ABSTRACT FROM AUTHOR]

Clear understanding the mechanism of resistive switching is the important prerequisite for the realization of high performance nonvolatile resistive random access memory. In this paper, binary metal oxide MoOx layer sandwiched by ITO and Pt electrodes was taken as a model system, reversible transition of abnormal and normal bipolar resistive switching (BRS) in dependence on the maximum voltage was observed. At room temperature, below a critical maximum voltage of 2.6 V, butterfly shaped I-V curves of abnormal BRS has been observed with low resistance state (LRS) to high resistance state (HRS) transition in both polarities and always LRS at zero field. Above 2.6 V, normal BRS was observed, and HRS to LRS transition happened with increasing negative voltage applied. Temperature dependent I-V measurements showed that the critical maximum voltage increased with decreasing temperature, suggesting the thermal activated motion of oxygen vacancies. Abnormal BRS has been explained by the partial compensation of electric field from the induced dipoles opposite to the applied voltage, which has been demonstrated by the clear amplitude-voltage and phase-voltage hysteresis loops observed by piezoelectric force microscopy. The normal BRS was due to the barrier modification at Pt/MoOx interface by the accumulation and depletion of oxygen vacancies. [ABSTRACT FROM AUTHOR]

Transition metal-free half-metallicity recently has been the subject of intense research activity due to its potential in spintronics application. By employing density functional theory calculations, we revealed that F-intercalated GaN bilayers exhibit robust p orbital-based half-metallicity against the intercalant concentration and biaxial strain of −10% to 10%. The stable half-metallicity results from a spontaneous phase transition through Stoner instability and can be attributed to unusually high density of states near the Fermi level due to the quasi-flat bands. These findings provide a strategy to design transition-metal free half-metallic materials for futuristic spintronic applications. [ABSTRACT FROM AUTHOR]

Organic field-effect transistors (OFETs) with polymer charge-trapping dielectric, which exhibit many advantages over Si-based memory devices such as low cost, light weight, and flexibility, still suffer challenges in practical application due to the unsatisfied endurance characteristics and even the lack of fundamental of behind mechanism. Here, we revealed that the degradation of endurance characteristics of pentacene OFET with poly(2-vinyl naphthalene) (PVN) as charge-storage layer is dominated by the deep hole-traps in PVN by using the photo-stimulated charge de-trapping technique with the fiber-coupled monochromatic-light probes. The depth distribution of hole-traps in PVN film of pentacene OFET is also provided. [ABSTRACT FROM AUTHOR]

Mn-doped La(Fe,Si) 13 compounds have been demonstrated as excellent candidates for magnetic refrigeration applications. However, the origins of Mn-dependent magnetic properties are still unclear. Here, by employing density functional theory calculations and Monte Carlo simulations, the changes in magnetic moment, total magnetic exchange coupling constant J total , atomic local environment, and Curie temperature T C of Mn-doped La(Fe,Si) 13 compounds were investigated. Mn atoms were found to prefer 96i sites and anti-parallelly couple with Fe atoms. The reduction of total magnetic moments during Mn substitution originates from the decreasing magnetic moments of Fe and anti-ferromagnetic coupling between Mn and Fe. Moreover, Mn dopants lead to the decrease in J total and T C , and the analysis of atomic local environment indicates that the weakening of J total can be mainly attributed to the shrinkage of the intra-icosahedral bond between Fe-I and Fe-II. This work offers a theoretical comprehension of the fundamental magnetic properties of Mn-doped La(Fe,Si) 13 compounds. [Display omitted] [ABSTRACT FROM AUTHOR]

We explore scaling laws for adapting a bonded-sphere discrete element method (BS-DEM) model developed for woody structural mechanics at the millimeter scale to model the mechanics of realistic lignocellulosic biomass microstructures. Two scaling approaches, i.e., the reverse coarse graining (RCG) and equivalent bulk behavior (EBB), are proposed based on the classical mechanics principles and assessed in the single-particle compression and rectangular cuboid block tension tests. The EBB approach is recommended for BS-DEM models with general 3D geometries and is applied to simulate the microindentation test on a realistic microscale pinewood specimen. Simulations are performed to elucidate the impact of specimen thickness and loading position on the specimen's force–deformation behavior. The range of Young's modulus obtained from the calibrated BS-DEM simulations can match the experimental measurements. This is the first-of-its-kind study that has explored scale-bridging modeling approaches in biomass micromechanics and has proposed solutions based on BS-DEM models in the microscale. [Display omitted] • First-of-its-kind reverse scaling laws for bonded-sphere discrete element model. • Reverse coarse graining applicable for maintaining equivalent single-bond behavior. • Equivalent bulk behavior recommended for BS-DEM model with general 3D geometries. • Impact of specimen thickness and loading position on material response analyzed. • Young's moduli from simulations using EBB can match the experimental measurements. [ABSTRACT FROM AUTHOR]

The commercialization of bioenergy has been significantly limited by various material handling issues due to the poor flowability of granular biomass materials. Addressing these issues demands a fundamental understanding of flow physics and robust models to predict the multi-regime flow behavior of biomass particles. In this study, we investigated the multi-regime flow behavior of loblolly pine chips, a widely used bioenergy feedstock, through combined experiments and simulations. A quasi-static hypoplastic model and a cross-regime Drucker–Prager (DP)- μ (I) model were utilized and validated against inclined plane flow experiments to understand the quasi-static and dense flow behavior of milled pine chips. The results show that along the inclined plane, loblolly pine chips mainly present in heap flow (varying thickness along the plane), and in plane flow (iso-thickness along the plane) only when the inclination closes to the material's critical state internal friction angle. The results also show that the multi-regime DP- μ (I) model predicts a completely different velocity profile from the hypoplastic model. DP- μ (I) model can capture the flow behavior of pine chips in both flow regimes well but at the cost of extra parameter determination, and the shear-rate dependent rheology model can successfully capture the flow of elongated high-frictional particles. These findings advance the scientific understanding of the multi-regime flow behavior of granular biomass materials and shed light on formulating novel constitutive models to assist granular biomass handling in the bioenergy industry. [Display omitted] • A multi-regime constitutive model is formulated to model granular biomass flow. • Quasi-static and dense flow behaviors are studied with an inclined plane tester. • Shear rate dependency of elongated high-frictional particles are studied. • Flow patterns and stopping profiles are governed by flow regimes. [ABSTRACT FROM AUTHOR]

This study examines the role of nano B 4 C addition in improving the mechanical properties of Ti–6Al–4V (Ti64) alloys fabricated by laser melting deposition under as-built and heat-treated conditions. However, the enrichment of reinforcing phases generated by in situ production at grain boundaries causes a serious reduction in ductility, limiting the development of high-performance titanium matrix composites. To avoid this deficiency, the fabricated titanium matrix composites (TMCs) were subjected to three different heat treatment programmers, namely, subtransus heat treatment, supertransus heat treatment and triple heat treatment. The effects of B 4 C addition and heat treatment on microstructure, texture and mechanical properties were systematically investigated. The results show that TiB and TiC, synthesized in situ, promote the precipitation of α-Ti with a non-Burgess orientation relationship, and weakening the texture intensity of α-Ti. The ultimate tensile strength of the in situ synthesized (TiB + TiC) reinforced Ti64 composites is 1168 MPa, which is 35.5 % higher than the ultimate tensile strength of the Ti64 alloys. However, this effect resulted in a decrease in elongation at break to 2.5 %. An excellent combination of strength and fracture strain of 1060 MPa and 9.3 %, respectively, was simultaneously achieved for the heat-treated TMCs. The excellent ductility is mainly attributed to the microstructure consisting of primary equiaxed-α, ultrafine α s lamellar and retained β phase has been obtained after triple heat treatment. This finding offers significant guidance for the additive manufacturing of TMCs microstructures in order to attain the desired mechanical properties. [ABSTRACT FROM AUTHOR]

Abstract: We report non-saturating linear magnetoresistance (LMR) in silver-poor composite thin films of Ag10Ge15Te75 (AGT). The LMR increases with decreasing temperature and reaches a value of 110% at 200K under a magnetic field of 70kOe. The observed magnetoresistance is proportional to carrier mobility due to identical temperature dependencies. The microstructures of AGT films annealed at different temperature are investigated by TEM observations. The observed LMR effect is resulting from the inhomogeneous distribution of conductivity caused by highly conductive Ag2Te and GeTe4 precipitates, which generate a current distortion in the surrounding amorphous silver-poor Ag–Ge–Te matrix. [Copyright &y& Elsevier]

With the advancement of renewable energy, the processing and handling of biomass feedstocks has drawn enormous research interest. The key to economically viable and operationally reliable biomass handling processes involves a complete understanding of the flow behavior of different feedstocks as functions of the inherent critical material properties environmental conditions, and critical processing parameters. This review introduces the basic principles and methods in bulk solids flow and highlights recent efforts to understand the flow behavior of biomass feedstocks. The effects of inherent properties, environmental parameters, and handling equipment on the flow behavior of biomass feedstocks are presented. Particle size, shape, moisture, consolidation stress, temperature, storage time at rest, chemical treatment, and the material and geometry of the handling equipment all substantially influence biomass flowability. The limitations of current studies and the potential methods to overcome them are presented. Finally, an outlook for future research effort is provided, with proposed opportunities for improving the characterization of biomass flow. [Display omitted] [ABSTRACT FROM AUTHOR]

The growth of Ag-nanofilaments in the solid electrolyte films of memristors based on Ag30S2P14O42 is investigated. After the formation of the Ag-nanofilaments in the solid electrolyte, the memory cells are switched to the high conductive state. With a positive voltage applied on the Ag electrode of the cells, the Ag-nanofilaments gradually become thicker due to the reduction and diffusion of Ag+ cations in the solid electrolyte. The relationship between the thickening rate of the Ag-nanofilaments and the concentration of the Ag+ cations surrounding them is analyzed, and the results show that the thickening of the Ag-nanofilaments is determined by the reduction and diffusion of Ag+ cations in the solid electrolyte. [ABSTRACT FROM AUTHOR]