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In this paper, we designed double V-shaped Al/Ni multilayer energy-containing microdevices with different V-angles, and we performed finite element modeling and simulation of the heat transfer process of the designed energy-containing microdevice. Temperature-dependent resistivity was introduced to effectively simulate the phase change during ignition. We simulated the temperature and current density distribution in the central region of the Al/Ni multilayer energy-containing microdevice and predicted the ignition voltage threshold for the specific device structure. Al/Ni multilayer energy-containing microdevices with different V-angles were prepared by electron beam evaporation technology, and ignition experiments on the prepared devices under the excitation of 47 μF capacitance were conducted. The experimental results show that the critical voltage of ignition increases with the increase in the V-angle, which verifies the correctness of the proposed finite element model. [ABSTRACT FROM AUTHOR]

Oxygen vacancies play a crucial role in stabilizing the ferroelectric phase in hafnium (Hf) oxide-based thin films and in shaping the evolution of their ferroelectric properties. In this study, we directly manipulated the oxygen vacancy concentration in Hf0.5Zr0.5O2−x (HZO) ferroelectric thin films in situ using oxygen plasma treatment. We scrutinized the variations in the ferroelectric properties of HZO films across different oxygen vacancy concentrations by integrating the findings from ferroelectric performance tests. Additionally, we elucidated the mechanism underlying the influence of oxygen vacancies on the coercive field and polarization properties of HZO ferroelectric films through the first-principles density functional theory (DFT) calculations. Finally, to study the impact of oxygen vacancies on the practical application of HZO ferroelectric synaptic devices, leveraging the plasticity of the ferroelectric polarization, we constructed a multilayer perceptron (MLP) network. We simulated its recognition accuracy and convergence speed under different oxygen vacancy concentrations in the MNIST recognition task. [ABSTRACT FROM AUTHOR]

Doping with various cations is considered to be a key method for inducing ferroelectricity in HfO2. However, previous studies often neglected the role of carriers introduced by heterovalent dopants. Here, using first-principles calculations, we show that carriers profoundly affect the stability of polar phases and advocate that carriers should be considered as a fundamental framework for understanding the origin of ferroelectricity in doped HfO2. Although doping with p-type elements that introduce holes can stabilize the polar phase, it is not sufficient to make them the ground state phase. However, when they are co-doped with an n-type V element, they not only stabilize the polar phase to the ground state, but also achieve charge neutrality through electron compensation. This is due to the formation of deep energy levels (electron–hole recombination centers) by V doping, similar to oxygen vacancies. Unlike oxygen vacancy compensation, which favors the formation of tetragonal phases, co-doping is more favorable for the formation of polar phases and the absence of structural defects. Our results contribute to the understanding of the origin of HfO2 ferroelectricity and provide a potential method for the preparation of HfO2-based films with excellent ferroelectric properties. [ABSTRACT FROM AUTHOR]

The γ‐ray total dose radiation effects on Zr‐doped HfO2 (HfZrO) and Al‐doped HfO2 (HfAlO) ferroelectric thin films are comparatively studied. The J–E, P–E,C–V, εr–f curves and fatigue characteristics of both HfZrO and HfAlO thin films are measured and analyzed with the increasing total dose from 0 to 5 Mrad (Si). The remnant polarization (Pr) values of both HfZrO and HfAlO thin films first decrease and then increase with the increasing total dose. A competitive mechanism between the pinned domains and increasing polarization switching charges induced by radiation is proposed to explain this phenomenon. This work presents doped HfO2 film with great radiation tolerance for nuclear and aerospace applications. [ABSTRACT FROM AUTHOR]

The oxygen ion (O2−) loss effect during resistive switching (RS) cycles will inevitably lead to endurance degradation or even failure in oxide-based memristive devices. In this Letter, we propose an effective way to recover the cycling-induced endurance failed HfOx based memristive devices by utilizing oxygen plasma treatment (OPT). In the as-fabricated Pt/HfOx/Pt devices, a negative SET event is observed after consecutive normal RS cycles and eventually triggers endurance failure. The appearance of the intermediate resistance state at the initial stage of the negative SET cycle indicates a prominent reduction of the migration barrier of O2−, which accounts for the occurrence of negative SET after increasing cycles. Then, we recover the devices from endurance failure by moderate OPT, which can supply the available O2− in RS cycles. More importantly, the first recovered devices after endurance failure can be recovered again through OPT, which better proves the validity of the recovery method. This study could provide an effective approach for understanding and addressing the cycling-induced endurance failure issue in oxide-based memristive devices. [ABSTRACT FROM AUTHOR]

The usage of ferroelectric-gate field effect transistors (FeFET) in digital circuits has typically been its applications in memory. The use of FeFET to implement logic circuits is neither completely understood nor extensively studied. This paper presents simulations of electrical properties of a single FeFET and the resulting behavioral characterizations of FeFET-based basic logic circuits in a commercially available TCAD environment. The all-FeFET current mirror, CMOS inverter, 2-input-NAND and 2-input-NOR logic circuits show almost the same electrical characteristics as standard MOSFET ones, except for the negligible clockwise hysteresis under the condition of low voltage supply. Moreover, the all-FeFET current mode sensitive amplifier whose component units were all-FeFET common-source amplifier, current mirror and differential amplification, also works reasonably. [ABSTRACT FROM AUTHOR]

Perovskite ferroelectrics (FEs) have high endurance to radiation. Strontium titanate (STO) (SrTiO3) is a kind of perovskite FE with a large dielectric constant, which has attracted a good deal of attention due to its excellent dielectric, photoelectric and optical properties. The proton radiation damage in STO thin films is investigated by computer simulations in this work. The threshold displacement energy is an important input parameter for Monte Carlo simulation based on a binary collision approximation model, so we first use molecular dynamics to calculate the averaged threshold displacement energy of Sr, O and Ti atom. The calculated values are 67, 50 and 136 eV, which are obviously larger than default value (25 eV) in the Stopping and Range of Ions in Matter (SRIM) code. The results of the SRIM simulation demonstrate the dependency of vacancy number and position distribution on the proton's energy and the angle of incidence. [ABSTRACT FROM AUTHOR]

Oxygen ions' migration is the fundamental resistive switching (RS) mechanism of the binary metal oxides-based memristive devices, and recent studies have found that the RS performance can be enhanced through appropriate oxygen plasma treatment (OPT). However, the lack of experimental evidence observed directly from the microscopic level of materials and applicable understanding of how OPT improves the RS properties will cause significant difficulties in its further application. In this work, we apply scanning probe microscope (SPM)-based techniques to study the OPT-enhanced RS performance in prototypical HfOx based memristive devices through in situ morphology and electrical measurements. It is first found that the structural deformations in HfOx nanofilm induced by migration of oxygen ions and interfacial electrochemical reactions can be recovered by OPT effectively. More importantly, such structural deformations no longer occur after OPT due to the strengthening in lattice structure, which directly illustrates the enhanced quantity of HfOx nanofilm and the nature of enhanced RS properties after OPT. Finally, the underlying mechanisms of OPT-enhanced RS performance are analyzed by the results of X-ray photoelectron spectroscopic (XPS) surface analysis. In the OPT-enhanced HfOx nanofilm, oxygen vacancies in crystalline regions can be remarkably reduced by active oxygen ions' implantation. The oxygen ions transport will depend considerably on the grain boundaries and OPT-enhanced lattice structure will further guarantee the stability of conductive filaments, both of which ensure the uniformity and repeatability in RS processes. This study could provide a scientific basis for improving RS performance of oxides-based memristive devices by utilizing OPT. [ABSTRACT FROM AUTHOR]

Bi3.15Nd0.85Ti2.99Mn0.01O12 (BNTM) thin films with (200)-orientations, (117)-orientations, and mixed-orientations were prepared by sol-gel methods. The influence of orientations on polarization fatigue behaviors of BNTM thin films were systematically investigated at both low and elevated temperatures. It was found that the changed trends of the polarization fatigue of (200)-oriented and (117)-oriented BNTM thin films at elevated temperatures were opposite. The fatigue properties become exacerbated for the (200)-oriented ones and become improved for the (117)-oriented ones, while the reduction of remanent polarization first decreases and then increases for the mixed-oriented ones. It can be assumed that the different roles played by domain walls and interface layer with increasing T in these thin films have caused such differences, which was certified by the lower activation energies (0.12–0.13 eV) of (200)-oriented BNTM thin films compared to those of BNTM thin films (0.17–0.31 eV) with other orientations through the temperature-dependent impedance spectra analysis. With the aid of piezoresponse force microscopy (PFM), the non-neutral tail-to-tail or head-to-head polarization configurations with greater probabilities for (117)-oriented and mixed-oriented thin films were found, while a majority of the neutral head-to-tail polarization configurations can be observed for (200)-oriented ones. [ABSTRACT FROM AUTHOR]

Bi4Ti2.99Mn0.01O12 (BTM) thin films with different ratio of neodymium (Nd) doping were prepared on Pt(111)/Ti/SiO2/Si(100) substrates through a sol-gel method. The effects of Nd doping on domain dynamics and temperature-dependent fatigue behaviors of BTM thin films were systematically studied. The polarization fatigues of BTM (not doped) and Bi3.5Nd0.5Ti2.99Mn0.01O12 (BNTM05) thin films first get better with the increasing temperature (T) from 300 to 350 K and then become worse from 350 to 400 K, while Bi3.15Nd0.85Ti2.99Mn0.01O12 (BNTM85) thin films show enhanced fatigue endurance from 300 to 400 K. It can be shown that the long-range diffusion of oxygen vacancies in BTM thin film happens more easily through the impedance spectra analysis with T from 300 to 475 K, which can be verified by a lower activation energies (0.13–0.14 eV) compared to those of BNTM05 and BNTM85 (0.17–0.21 eV). Using a temperature-dependent piezoresponse force microscopy (PFM), we have found more responsive domain fragments in Nd-substituted films. The microscopic domain evolution from 298 to 448 K was done to further explain that the domain wall unpinning effect has been enhanced with increasing T. The correlation between microscopic domain dynamics and macroscopic electrical properties clearly demonstrates the effects of charged domain wall in Nd-doped BTM thin films during the fatigue tests. [ABSTRACT FROM AUTHOR]

The friction behavior of monolayer molybdenum diselenide (MoSe 2) under normal electric field was studied by the atomic force microscope. The friction coefficients of MoSe 2 are increasing with bias voltage applied on the Si substrate. The results show that the adhesion and electrostatic forces increase with bias and approximately follow a parabolic law. The friction force and surface potential are of the same tendency with bias application time, and the contribution of charges accumulation to friction is considerable. The mechanisms of the friction behavior under external normal electric field were explained with electrostatic force and adsorption. This study reveals a possibility of electronically controlling friction in two-dimensional MoSe 2 system, with potential applications in solid lubricant and moving parts for MEMS devices. • The friction behavior of monolayer MoSe 2 nanosheet can be modulated under normal electric field investigated by the AFM. • The friction coefficient, adhesion force and electrostatic force increase with the sample bias. • The mechanisms of friction behaviors under normal electric field were explained with electrostatic force and absorption. • A possibility of electronically controlling friction is provided in 2D MoSe 2 system. [ABSTRACT FROM AUTHOR]

Polar metals, commonly defined by the coexistence of polar structure and metallicity, are thought to be scarce because free carriers eliminate internal dipoles that may arise owing to asymmetric charge distributions. By using first-principle electronic structure calculations, we explored the possibility of producing metallic states in the polar/nonpolar KNbO 3 /BaTiO 3 superlattice (SL) composed of two prototypical ferroelectric materials: BaTiO 3 (BTO) and KNbO 3 (KNO). Two types of polar/nonpolar interfaces, p-type (KO) - /(TiO 2 ) 0 and n-type (NbO 2 ) + /(BaO) 0 , which can be constituted into two symmetric NbO 2 /BaO-NbO 2 /BaO (NN-type) and KO/TiO 2 -KO/TiO 2 (PP-type) SL, as well as one asymmetric KO/TiO 2 -NbO 2 /BaO (PN-type) SL. The spatial distribution of ferroelectric distortions and their conductive properties are found to be extraordinarily sensitive to the interfacial configurations. An insulator-to-metal transition is found in each unit cell of the symmetric interfacial SL models: one exhibiting quasi-two-dimensional n-type conductivity for NN-type SL, while the other being quasi-two-dimensional p-type conductivity for PP-type SL. The anisotropic coexistence of in-plane orientation of free carriers and out-of-plane orientation of ferroelectric polarization in KNO/BTO SL indicates that in-plane free carriers can not eliminate the out-of-plane dipoles. Our results provide a road map to create two-dimensional polar metals in insulating perovskite oxide SL, which is expected to promote applications of new quantum devices., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

Bi₄Ti 2.99 Mn 0.01 O 12 (BTM) thin films with different ratio of neodymium (Nd) doping were prepared on Pt(111)/Ti/SiO₂/Si(100) substrates through a sol-gel method. The effects of Nd doping on domain dynamics and temperature-dependent fatigue behaviors of BTM thin films were systematically studied. The polarization fatigues of BTM (not doped) and Bi 3.5 Nd 0.5 Ti 2.99 Mn 0.01 O 12 (BNTM05) thin films first get better with the increasing temperature ( T ) from 300 to 350 K and then become worse from 350 to 400 K, while Bi 3.15 Nd 0.85 Ti 2.99 Mn 0.01 O 12 (BNTM85) thin films show enhanced fatigue endurance from 300 to 400 K. It can be shown that the long-range diffusion of oxygen vacancies in BTM thin film happens more easily through the impedance spectra analysis with T from 300 to 475 K, which can be verified by a lower activation energies (0.13⁻0.14 eV) compared to those of BNTM05 and BNTM85 (0.17⁻0.21 eV). Using a temperature-dependent piezoresponse force microscopy (PFM), we have found more responsive domain fragments in Nd-substituted films. The microscopic domain evolution from 298 to 448 K was done to further explain that the domain wall unpinning effect has been enhanced with increasing T . The correlation between microscopic domain dynamics and macroscopic electrical properties clearly demonstrates the effects of charged domain wall in Nd-doped BTM thin films during the fatigue tests.