Search

Perovskite oxides and organic–inorganic halide perovskite materials, with numerous fascinating features, have been subjected to extensive studies. Most of the properties of perovskite materials are dependence on their ferroelectricity that denoted by remanent polarization (Pr). Thus, the increase of Pr in perovskite films is mainly an effort in material physics. At present, commonplace improvement schemes, i.e., controlling material crystallinity, and post‐annealing by using a high‐temperature process, are normally used. However, a simpler and temporal strategy for Pr improvement is always unavailable to perovskite material researchers. In this study, an organic coating layer, low‐temperature, and vacuum‐free strategy is proposed to improve the Pr, directly increasing the Pr from 36 to 56 µC cm−2. Further study finds that the increased Pr originates from the suppression of the oxygen defects and Ti defects. This organic coating layer strategy for passivating the defects may open a new way for the preparation of higher‐performance and cost‐effective perovskite products, further improving its prospective for application in the electron devices field. [ABSTRACT FROM AUTHOR]

With the development of artificial intelligence technology, it remains a challenge to improve the resistive switching performance of next-generation nonvolatile ferroelectric memristor device (FMD). Here, we report an epitaxial Na0.5Bi0.5TiO3 ferroelectric memristor device (NBT-FMD) with temperature sensing. The NBT epitaxial films with strong polarization strength and suitable oxygen vacancy concentration were obtained by temperature adjustment (700 °C). In addition, the function of the spiking-time-dependent plasticity and paired-pulse facilitation is simulated in ferroelectric memristor devices of Pt/NBT/SrRuO3 (SRO)/SrTiO3 (STO). More importantly, we have designed a neuronal circuit to confirm that NBT-FMD can serve as temperature receptors on the human skin, paving the way for bio-inspired application. [ABSTRACT FROM AUTHOR]

In this paper, we study the existence of the families of odd symmetric periodic solutions in the generalized elliptic Sitnikov (N + 1) -body problem for all values of the eccentricity e ∈ [ 0 , 1) using the global continuation method. First, we obtain the properties of the period of the solution of the corresponding autonomous equation (eccentricity e = 0 ) using elliptic functions. Then, according to these properties and the global continuation method of the zeros of a function depending on one parameter, we derive the existence of odd periodic solutions for all e ∈ [ 0 , 1) . It is shown that the temporal frequencies of period solutions depend on the total mass λ (or the number N) of the primaries in a delicate way. [ABSTRACT FROM AUTHOR]

Electronic synaptic devices with photoelectric sensing function are becoming increasingly important in the development of neuromorphic computing system. Here, we present a photoelectrical synaptic system based on high-quality epitaxial Ba0.6Sr0.4TiO3 (BST) films in which the resistance ramp characteristic of the device provides the possibility to simulate synaptic behavior. The memristor with the Pt/BST/Nb:SrTiO3 structure exhibits reliable I–V characteristics and adjustable resistance modulation characteristics. The device can faithfully demonstrate synaptic functions, such as potentiation and depression, spike time-dependent plasticity, and paired pulse facilitation, and the recognition accuracy of handwritten digits was as high as 92.2%. Interestingly, the functions of visual perception, visual memory, and color recognition of the human eyes have also been realized based on the device. This work will provide a strong candidate for the neuromorphic computing hardware system of photoelectric synaptic devices. [ABSTRACT FROM AUTHOR]

Epitaxial (Pb0.9La0.1)(Zi0.4Ti0.6)O3 (PLZT) film was prepared with Pt as the upper electrode and La0.5Sr0.5CoO3(LSCO) as the bottom electrode on (001) STO substrate by radio frequency (RF) magnetron sputtering. The dynamic hysteresis scaling behavior of the film, including the variation of remanent polarization (Pr), coercive field (Ec), and loop area () with external field (E0) and frequency (f) , was systematically studied. The evolution of scaling behavior in the PLZT film can be divided into two stages: minor loops and major loops, which are in the low and high E0 regions, respectively. The scaling relations take form of < A > ∝ f − 0.11 E 0 2.72 and < A > ∝ f − 0.03 E 0 1.27 in minor loops and major loops, respectively. The results show that the domain structure and domain reversal play an important role in the dynamic hysteresis behavior of ferroelectric materials. [ABSTRACT FROM AUTHOR]

Obtaining an ideal ferroelectric photovoltaic (FE-PV) material with a narrow bandgap and a large ferroelectric polarization value can enable us to achieve great practical FE-PV performance. By the introduction of sulfur into the tetragonal BiCoO3 perovskite with a C-type antiferromagnetic ordering, it is found that the bandgap of BiCoO2S decreases significantly (about 1.2 eV) while maintaining a large polarization value (about 1.86 C m−2) that is similar to the value of 1.793 C m−2 of BiCoO3. Most noteworthy is that the optical absorption of BiCoO2S is remarkably higher than those of BiCoO3 and other FE-PV materials. The decrease of the BiCoO2S bandgap originates from the movement of Co 3d states to a low-energy position due to the reduction of the Co ionicity when the less electronegative sulfur is introduced into BiCoO3 to substitute oxygen. The narrow bandgap and the high optical absorption of the BiCoO2S films grown on different substrates are favorable for FE-PV applications. In addition, the bandgap of BiCoO2S can be modulated by the doping amount of sulfur, which can help us fabricate multilayer FE-PV devices based on different bandgaps from different layers. [ABSTRACT FROM AUTHOR]

Understanding the L10 phase transformation of FePt nanocrystals in FePt:X (X = nonmagnetic materials) nanocomposite thin films is of particular importance for controlling and designing these films as ultrahigh density magnetic recording media. In this study, by employing temperature- and pressure-dependence of the rate constant of phase transition, the nucleation (En = 0.3 eV) and growth (Eg = 0.9 eV) activation energies of L10 ordered domains, as well as an activation volume ΔV* ≈ 0.96 Ω (Ω = average atomic volume) for L10 ordering transition in FePt:Ag nanocomposite thin films have been successfully determined. These data suggest that the growth of L10 ordered domains is predominantly dependent on the diffusion of Fe atoms in FePt crystals, and that the diffusion of Ag atoms out of FePt lattice prompts the nucleation of the L10 ordered domains. These findings have a direct implication for designing FePt:Ag nanocomposite thin films with high pack fraction of L10-FePt nanocrystals. [ABSTRACT FROM AUTHOR]

We have measured the pressure dependence of the growth of α-Fe and Nd2Fe14B nanocrystals in amorphous Nd9Fe85B6 up to 6 GPa at a temperature of 923 K, yielding an activation volume of ΔV*=(0.76±0.04) and (0.57±0.05)Ω for atomic diffusion in the growth process of α-Fe and Nd2Fe14B nanocrystals, respectively, where Ω is the mean atomic volume of the alloy. This demonstrates that the growth of nanocrystals is dependent on atomic diffusion mediated by vacancy-type thermal defects. Atomic processes of the growth of nanocrystals are discussed. [ABSTRACT FROM AUTHOR]