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The solid-electrolyte-based memristors have attracted tremendous attention for the next-generation nonvolatile memory for both logic and neuromorphic applications. However, they encounter variability performance challenges which originated from the random ionic transport and conductive filaments formation. Evidently, the electrochemical metallized mechanism associated with ion transport has been elucidated. Nonetheless, the failure mechanism caused by ion transport during cycles is rarely reported. Hereafter, the five stages of failure in the Ag/Ag10Ge15Te75/W memristor are elucidated through ex-situ current-voltage measurements combined with in-situ transmission electron microscopy characteristics. Our investigation reveals that the migration and enrichment of Ag ions result in the precipitation of Ag2Te. The formation of Ag2Te hinders the device's ability to maintain its bipolar characteristics and also decreases the resistance value of the high resistance state, thereby reducing the device's switching ratio. The promising results provide important guidance for the future design of structures and the manipulation of ion transport for high-performance memristors. [ABSTRACT FROM AUTHOR]

Perovskite‐oxide‐based ferroelectric tunnel junctions (FTJs) hold great potential for applications in non‐volatile memory and neuromorphic computing due to their unique properties. However, the challenges in synthesizing high crystalline quality perovskite oxides directly on silicon wafer limit the applications of these FTJs in conventional Si‐based integrated circuits, let alone the neural networks. Herein, perovskite oxide FTJs with an ON/OFF ratio up to 1.2×106, writing/erasing speed down to 1 nanosecond, and cycling endurance (>106) are achieved by integrating ultrathin freestanding ferroelectric perovskite oxide membranes directly on silicon wafers using a wet‐transfer method. Moreover, synapses based on these FTJs exhibit long‐term plasticity. For handwritten digits recognition task, the convolutional neural network (CNN) simulation is implemented achieving a recognition accuracy up to 98.9% based on the experimental performance, close to the result of 99.2% by software‐floating‐point‐based CNN. This work sheds light on the integration of ferroelectric perovskite oxides directly on silicon for high‐performance FTJ‐based non‐volatile memory and synaptic devices. [ABSTRACT FROM AUTHOR]

Organic field‐effect transistors (OFETs) hold great promise for applications in non‐volatile memories, detectors, and artificial synapses due to the good flexibility and biocompatibility. However, certain drawbacks such as high operating voltages and significant degradation in endurance characteristics have hindered their practical implementations. Herein, a novel approach is proposed to enhance the performance of OFETs by incorporating a bi‐functional n‐type polymer semiconductor interlayer, Poly‐{[N,N'‐bis(2‐octyldodecyl)naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (N2200), into a pentacene OFET structure. The device exhibits remarkable improvements, with reliable P/E operation cycles of over than 104 and a retention time of more than 10 years. On one hand, the inclusion of N2200 as an n‐type semiconductor effectively reduces the height of hole‐injection barrier for trapping and thus reducing the working voltage based on the electrostatic induction theory. On the other hand, n‐type semiconductor N2200 serves as a native hole‐consumption (or hole‐trapping) dielectric, and its narrower bandgap restrains the formation of deep hole‐traps, thus favoring the endurance characteristics of the OFET. [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]

Organic field‐effect transistor (OFET) memory based on pentacene has attracted a lot of attentions due to its promising prospect of application in flexible electronics, while the high programming/erasing (P/E) gate voltages due to the existence of hole barrier at pentacene/polymer interface leaves great challenges for its commercial applications. A high‐performance pentacene‐based OFET nonvolatile memory (ONVM) with polymer blends is reported here as the charge‐trapping layer containing poly(2‐vinyl naphthalene) (PVN) and poly{[N,N'‐bis(2‐octyldodecyl)naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5'‐(2,2'‐bithiophene)} (N2200). The presence of N2200, an n‐type semiconductor, in blends significantly improves the memory performance of pentacene‐based memory devices based on the static‐electric effect. The electrons in N2200 are aggregated near the pentacene/polymer interface due to the electric attraction from the positively charged defects in pentacene. Furthermore, those electrons reduce the height of hole barrier and produce local easy‐transportation paths for holes between pentacene and PVN, which enables the electret‐based ONVM device with low P/E voltages, fast P/E speeds, large mobility and stable multilevel data‐storage ability in ambient air. [ABSTRACT FROM AUTHOR]

The many-body dissipative particle dynamics (mDPD) is a prominent mesoscopic multiphase model for fluid transport in mesoconfinement. However, it has been a long-standing challenge for mDPD (and other multiphase-enabled DPD models) to accurately predict real-fluid static and dynamic properties simultaneously. We have developed a modified mDPD model to overcome the issue and a rigorous calibration approach that uses reference data, including experimental and/or molecular dynamics (MD) simulations to parameterise the modified mDPD for real fluids. We choose heptane as a representative example of hydrocarbon in source rocks to demonstrate the model's capability to accurately predict the equation of state (EOS), free surface tension, diffusivity, and viscosity. Our timing test shows that the modified mDPD is 400–500 times faster than its MD counterpart for simulating bulk heptane in equivalent volumes. To further demonstrate the robustness of the model, we revisited the benchmark problem of mesoscopic modelling of water, in which all the previous works on DPD reported only a limited portion of the water properties. We show that the modified mDPD can provide accurate modelling of water static and dynamic properties and an EOS that matches the experimental data to a large range of confinement pressure. [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]

The synapse is one of the fundamental elements in human brain performing functions such as learning, memorizing, and visual processing. The implementation of synaptic devices to realize neuromorphic computing and sensing tasks is a key step to artificial intelligence, which, however, has been bottlenecked by the complex circuitry and device integration. We report a high-performance charge-trapping memory synaptic device based on two-dimensional (2D) MoS2 and high-k Ta2O5–TiO2 (TTO) composite to build efficient and reliable neuromorphic system, which can be modulated by both electrical and optical stimuli. Significant and essential synaptic behaviors including short-term plasticity, long-term potentiation, and long-term depression have been emulated. Such excellent synaptic behaviors originated from the good nonvolatile memory performance due to the high density of defect states in the engineered TTO composite. The 2D synaptic device also exhibits effective switching by incident light tuning, which further enables pattern recognition with accuracy rate reaching 100%. Such experimental demonstration paves a robust way toward a multitask neuromorphic system and opens up potential applications in future artificial intelligence and sensing technology. [ABSTRACT FROM AUTHOR]

Recent years have witnessed the emergence of visible‐light‐stimulated synaptic transistors, which has potential for the construction of visual cognition and light‐controlled neuromorphic hardware. Efforts are made to improve the visible light‐stimulated plasticity by boosting the synaptic weight after optical neural activities. However, such modulation at the expense of increased initial synaptic weight before the stimuli still results in the limited plasticity. Here, instead of employing those inherent interfacial trap‐induced effects that raise the activated synaptic weight, it is demonstrated that an interfacial modification to inhibit them can greatly reduce the initial synaptic weight. Hence, with the assistance of the charge‐trapping memory effect, the initial and the activated synaptic weight can be modulated, leading to a significantly enhanced plasticity. Such enhancement is accomplished in a type of pentacene‐based synaptic transistors in which a visible‐light‐triggered plasticity above 108% (at 0 V gate voltage and −1 V source–drain voltage) can be achieved under a moderate optoelectronic stimulus. As a demonstration, long‐term potentiation is implemented to showcase synaptic responses with high plasticity after repeated light‐triggered neural activities, suggesting the proposed mechanism and design paradigm would be beneficial for future optical neuromorphic architectures. [ABSTRACT FROM AUTHOR]

Theoretical and experimental work has revealed that a positively charged insulator layer formed by oxygen‐related defects near pentacene–dielectric interface in organic field‐effect‐transistors (OFETs) severely affects their performance. A novel OFET memory structure with an n‐type organic buffer layer at the pentacene/polymer interface is proposed. In this structure, electrons are induced on the surface of the n‐type organic layer near the interface due to the electrostatic field of the positively charged insulator and partly compensate the local positive charges at the interface, leading to a reduction in the height of hole barrier formed at the interface. On the other hand, the positive space charges will be induced in an extended region in n‐type organic layer due to the limited density of ionized donors, blocking the back transfer of holes to pentacene as a result of the thicker positively charged layer. This idea is implemented in the n‐type PTCDI‐C13‐buffered OFETs with poly(2‐vinyl naphthalene) (PVN) dielectric, in which greatly reduced P/E gate voltages, reliable P/E endurance of more than 10 000 cycles, and excellent retention time of more than 104 s with an ION/IOFF of more than 104 under a set of P/E pulses with low amplitudes and short pulses are achieved in air. [ABSTRACT FROM AUTHOR]

With structural miniaturization down to the nanoscale, some detectable parameters of materials no longer remain constant. For NiO nanoparticles example, Raman shift and Néel temperature increase while optical band gap decreases with increasing the nanoparticle size. Herein, we developed the analytic models to describe the size dependence of these above-mentioned seemingly uncorrelated parameters for NiO nanoparticles, based on the average coordination number-dependent cohesive energy model. Consistency between our theoretical predictions and the corresponding experimental results not only verified the accuracy of our developed models but also provided insight into the essentiality of cohesive energy in describing the effect of size on the materials properties of NiO nanoparticles. [ABSTRACT FROM AUTHOR]

A nonvolatile memory structure with a high-k composite of ZnO-TiO2 as a charge-trapping dielectric was fabricated by using rf-sputtering and atomic layer deposition techniques, in which the potential of the conduction-band minimum of the composite was designed to be lower than that of Si by the use of the special energy-band offsets among Si, ZnO, and TiO2. Compared to the conduction-band minimum of Si, a relatively negative potential of the high-k composite leads to a continuous rise in the shift of the flat-band potential of the memory device except a drop at the beginning part of the time-dependent retention curve after a programming operation. The drop was attributed to the escape of trapped charges at the Si/Al2O3 interface. After extracting the contribution to the deterioration of the retention curve from the traps at the Si/Al2O3 interface, it was identified that the band alignment in a charge-trapping memory device dominated its retention behaviors. [ABSTRACT FROM AUTHOR]

Lead-free (1 − x)(0.8Bi0.5Na0.5TiO3-0.2SrTiO3)-xLiNbO3 (BNST-xLN, x = 0-0.08) piezoelectric ceramics were fabricated by a solid-state sintered technology. The effects of LN-doping on the structural and electrical properties of the BNST-xLN system were systematically investigated. The results of Raman spectroscopy revealed that the substitution of LN softens the phonon vibrations in the BNST-xLN system, in accordance with the remarkable reduction in the phase transition temperature (TF−R), remnant polarization (Pr), negative strain (Sneg) and piezoelectric coefficient (d33). However, the degradation of the long-range ferroelectric orders was accompanied by a significant increase in the electric field-induced strain response. At x = 0.04, a maximum unipolar strain of ~ 0.36% with a corresponding normalized strain (Smax/Emax) of ~ 600 pm/V was obtained at room temperature, which should be mainly ascribed to the reversibly electric field-induced phase transition between the ergodic relaxor and ferroelectric phases due to their comparable free energies in the two-phase coexistence region. Moreover, it was also found that the BNST-xLN system processes predominant electrostrictive behaviors with relatively high electrostrictive coefficient (Q33) and excellent temperature stability when the field-induced phase transition cannot be trigged by the applied electric field, as evidenced by a fact that the Q33 value of BNST-0.08LN ceramic keeps almost constant as high as ~ 0.028 m4/C2 in the temperature range from room temperature to 120 °C. [ABSTRACT FROM AUTHOR]

Band alignments of La2Hf2O7 (LHO) films grown on fully depleted SiGe on insulator (FD SGOI) substrates have been investigated by x-ray photoelectron technique. The valence and conduction band offsets for LHO/FD SGOI systems are determined to be 3.25 and 1.49 eV, respectively. Such asymmetric band alignment can be modulated to be quite symmetric by the surface nitridation of FD SGOI using NH3 treatment. The impact of NH3-treatment temperature on band offsets is also investigated. [ABSTRACT FROM AUTHOR]

Abstract: Neuromorphic optoelectronic devices with new functionality have attracted much attention since they can be applied in energy‐efficient computing and recognition. Here, a silicon optoelectronic device with a designed configuration resembling the retinal circuitry is reported. This kind of device composed of a silicon photoreceptor and a hafnium metal oxide synapse supports optoelectronic spike‐timing‐dependent plasticity that is manipulated completely by both optical and electrical stimuli. The optoelectronic plasticity allows the lasting modulation of photoresponses by using a transient optoelectronic stimulus. Stateful photoresponses can thus be regulated according to either the illumination intensity or the electrical compliance current. [ABSTRACT FROM AUTHOR]

Oxide-based binary resistive switching memories using metal nitride as one of the electrodes usually have a limited ratio of the resistances of the high- and low-resistance states. Here, we propose a competing mechanism to enhance the switching ratio by modifying the high-resistance state with extra inherent interfacial oxygen diffusion against what happens at the oxide/nitride interface. This is implemented in Pt/ZrO2/Ta2O5/TaN bilayer structures, where a resistance ratio above 104, about one to two orders of magnitude greater than that in Pt/Ta2O5/TaN monolayer structures, is achieved. This competing mechanism is further corroborated by the failed enhancement in the switching ratio when using an altered stacking arrangement of the two oxide layers. [ABSTRACT FROM AUTHOR]

Lead-free 0.985[(0.94− x)Bi0.5Na0.5TiO3-0.06BaTiO3- xSrTiO3]-0.015LiNbO3 [( BNT- BT- xST)- LN, x=0-0.05] piezoelectric ceramics were prepared using a conventional solid-state reaction method. It was found that the long-range ferroelectric order in the unmodified ( BNT- BT)- LN ceramic was disrupted and transformed into the ergodic relaxor phase with the ST substitution, which was well demonstrated by the dramatic decrease in remnant polarization ( Pr), coercive field ( Ec), negative strain ( Sneg) and piezoelectric coefficient ( d33). However, the degradation of the ferroelectric and piezoelectric properties was accompanied by a significant increase in the usable strain response. The critical composition ( BNT- BT-0.03 ST)- LN exhibited a maximum unipolar strain of ~0.44% and corresponding normalized strain, Smax/ Emax of ~880 pm/V under a moderate field of 50 kV/cm at room temperature. This giant strain was associated with the coexistence of the ferroelectric and ergodic relaxor phases, which should be mainly attributed to the reversible electric-field-induced transition between the ergodic relaxor and ferroelectric phases. Furthermore, the large field-induced strain showed relatively good temperature stability; the Smax/ Emax was as high as ~490 pm/V even at 120°C. These findings indicated that the ( BNT- BT- xST)- LN system would be a suitable environmental-friendly candidate for actuator applications. [ABSTRACT FROM AUTHOR]

FALCON (Fracturing And Liquid CONvection) is a hybrid continuous/discontinuous Galerkin finite element geothermal reservoir simulation code based on the MOOSE (Multiphysics Object-Oriented Simulation Environment) framework being developed and used for multiphysics applications. In the present work, a suite of verification and validation (V&V) test problems for FALCON was defined to meet the design requirements, and solved to the interests of enhanced geothermal system modeling and simulation. The intent for this test problem suite is to provide baseline comparison data that demonstrates the performance of FALCON solution methods. The test problems vary in complexity from a single mechanical or thermal process, to coupled thermo-hydro-mechanical processes in geological porous medium. Numerical results obtained by FALCON agreed well with either the available analytical solutions or experimental data, indicating the verified and validated implementation of these capabilities in FALCON. Whenever possible, some form of solution verification has been attempted to identify sensitivities in the solution methods, and suggest best practices when using the FALCON code. [ABSTRACT FROM AUTHOR]

In this work, we have fabricated and thoroughly characterized dielectric-stacked memory devices with AlO-CuO composites as the charge trapping layer which are prepared by using atomic layer deposition and RF-magnetron sputtering techniques. The devices exhibit a large memory window of 13.27 V and a density of the trapped charges of 9.37 × 10 cm at a working voltage of ±11 V. The microstructural observations by using high resolution transmission electron microscopy and the analysis on X-ray photoelectron spectroscopy indicate that the strong charge-trapping ability of AlO-CuO composite should be ascribed to the occurrence of Cu, resulted by the inter-diffusion at the interface of CuO/AlO. Such an interesting composite layer has very attractive application in nonvolatile memory. [ABSTRACT FROM AUTHOR]

The charge-trapping memory devices namely Pt/Al2O3/(Al2O(Cu2O)/SiO2/-Si with 2, 3 and 4 nm SiO2 tunneling layers were fabricated by using RF magnetron sputtering and atomic layer deposition techniques. At an applied voltage of ±11 V, the memory windows in the C- V curves of the memory devices with 2, 3 and 4 nm SiO2 tunneling layers were about 4.18, 9.91 and 11.33 V, respectively. The anomaly in memory properties among the three memory devices was ascribed to the different back tunneling probabilities of trapped electrons in the charge-trapping dielectric (Al2O(Cu2O) due to the different thicknesses of SiO2 tunneling layer. [ABSTRACT FROM AUTHOR]

A space and time third-order discontinuous Galerkin method based on a Hermite weighted essentially non-oscillatory reconstruction is presented for the unsteady compressible Euler and Navier-Stokes equations. At each time step, a lower-upper symmetric Gauss-Seidel preconditioned generalized minimal residual solver is used to solve the systems of linear equations arising from an explicit first stage, single diagonal coefficient, diagonally implicit Runge-Kutta time integration scheme. The performance of the developed method is assessed through a variety of unsteady flow problems. Numerical results indicate that this method is able to deliver the designed third-order accuracy of convergence in both space and time, while requiring remarkably less storage than the standard third-order discontinous Galerkin methods, and less computing time than the lower-order discontinous Galerkin methods to achieve the same level of temporal accuracy for computing unsteady flow problems. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

An OpenACC directive-based graphics processing unit (GPU) parallel scheme is presented for solving the compressible Navier-Stokes equations on 3D hybrid unstructured grids with a third-order reconstructed discontinuous Galerkin method. The developed scheme requires the minimum code intrusion and algorithm alteration for upgrading a legacy solver with the GPU computing capability at very little extra effort in programming, which leads to a unified and portable code development strategy. A face coloring algorithm is adopted to eliminate the memory contention because of the threading of internal and boundary face integrals. A number of flow problems are presented to verify the implementation of the developed scheme. Timing measurements were obtained by running the resulting GPU code on one Nvidia Tesla K20c GPU card (Nvidia Corporation, Santa Clara, CA, USA) and compared with those obtained by running the equivalent Message Passing Interface (MPI) parallel CPU code on a compute node (consisting of two AMD Opteron 6128 eight-core CPUs (Advanced Micro Devices, Inc., Sunnyvale, CA, USA)). Speedup factors of up to 24× and 1.6× for the GPU code were achieved with respect to one and 16 CPU cores, respectively. The numerical results indicate that this OpenACC-based parallel scheme is an effective and extensible approach to port unstructured high-order CFD solvers to GPU computing. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

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]

An effective method to generate traps at the interface was developed to enhance the charge trapping capability of HfO2/Al2O3 multilayered memory devices. A high charge density was obtained in the inter-diffusion layer in which additional trap sites could be created by thermal-treatment induced inter-diffusion. By keeping the consistent thickness of the charge trapping layer and increasing the number of the inter-diffusion layers, more traps can be introduced in the charge trapping layer. So, creating more trap sites by enhancing the inter-diffusion at the interface of different high-k dielectrics could be a potential choice for future memory applications. [ABSTRACT FROM AUTHOR]

ZrO nanocrystallites based charge trap memory cells by incorporating a (ZrO)(SiO) film as a charge trapping layer and amorphous AlO as tunneling and blocking layer were prepared and investigated. The precipitation reaction in charge trapping layer forming ZrO nanocrystallites during rapid thermal annealing was investigated by transmission electron microscopy. The density and size of ZrO nanocrystallites are the critical factors for controlling the charge storage characteristics. The ZrO nanocrystallites based memory cells after postannealing at 800 C for 60 s exhibit the best electrical characteristics and a low charge loss ∼5 % after 10 write/erase cycles operation. [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]

The structural and optical characterizations of titania incorporated with alumina nanocrystals have been presented in this paper and the films exhibit excellent properties like low current density, small hysteresis as well as high photoluminescence quantum yields of about 361 nm. These properties are promising for the applications in future electronic devices. [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]

Unipolar resistance switching characteristics are observed in fully transparent indium-doped SnO2/MgO/F-doped SnO2 device. In addition to the transmittance above 90% for visible light, the devices show good endurance and retention characteristics. The resistance-temperature relation curves and the corresponding Arrhenius plot confirm the semiconducting conduction behavior of both the high resistance state and the low resistance state. Experimental results indicate that Ohmic and trap controlled space-charge-limited conduction mechanism controlled the charge carriers transport at the low voltage and high voltage regions, respectively. This work presents a candidate material MgO for the application on the future see-through electronic devices. [ABSTRACT FROM AUTHOR]

The charge trapping memory devices based on different HfO2/Al2O3 nanolaminated charge trapping layers were prepared and investigated. The memory device with 6 interfaces HfO2/Al2O3 shows a memory window of 4.7 V in its capacitance-voltage curve and a better retention property. It was suggested that the thermal treatment would reduce the defects inside the bulk HfO2, but cause an inter-diffusion at the interface HfO2/Al2O3, which could create additional defects at HfO2/Al2O3 interface. Increasing the number of the interfaces could enhance the charge trapping capability of the devices. The band alignments were established to explain the variation trend of the memory window and the retention characteristics of the memory devices with different laminated structures. [ABSTRACT FROM AUTHOR]

Well-developed bipolar resistive switching behaviors have been revealed in Pt/GaOx/ITO stacks without an electroforming process. By substituting platinum with titanium as the top electrode, switching polarity changed from 'counter-Figure-8' to 'Figure-8.' The modulation of Schottky barrier at the Pt/GaOx interface induced by migration of oxygen vacancies was proposed to explain the switching in Pt/GaOx/ITO stacks, while the switching in Ti/GaOx/ITO stacks was ascribed to the redox reaction at the Ti/GaOx interface. Our experimental result further confirms the migration of oxygen vacancies in the vicinity of the electrode area plays an important role in the resistive switching process. [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]

Complex impedance spectroscopy has been employed to investigate the conduction behavior of (Ba,Sr)(Zr,Ti)O3 thin films in the low- and high-resistance states for resistive switching applications. The domination of the grain bulk effect on the resistive switching is demonstrated. The analyses of activation energies for the conduction in the low- and high-resistance states have been executed comparatively. It is proposed that the first and the second ionization of oxygen vacancies are responsible for the conduction in the low- and high-resistance states, respectively. The transition of conduction mechanism is also discussed. [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]

Polycrystalline (Ba,Sr)(Zr,Ti)O3 thin films sandwiched between two Pt electrodes have been revealed to exhibit hysteretic current-voltage (I-V) characteristics and resistive switching at room temperature. High- and low-resistance states, as well as a less abrupt state transition, occur during the voltage cycle. The maximum ratio between these two resistance states is about 230. Analyses of I-V behaviors have been executed, and it is proposed that space-charge-limited-current conduction in higher voltage region caused by asymmetric electron trapping centers is responsible for such transition of resistance states. [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]