SrTiO3 Layer Research Articles

Artificial design of anisotropic magnetoelectric effect in Sr2IrO4/SrTiO3 superlattices

Magnetoelectric response in thin films is highly desirable for high-throughput and high-density microelectronic applications, like magnetic sensors. To sensitively detect the direction of magnetic field, the anisotropic magnetoelectric effect is required. Here, we artificially design an anisotropic magnetoelectric response in Sr2IrO4/SrTiO3 superlattices, where a strong (negligible) magnetoelectric response for magnetic fields along the z-direction (xy-plane) of Sr2IrO4/SrTiO3 interface was observed. A combination of perturbative calculations with numerical results and density functional theory calculations reveals that only the effective z-component Zeeman field within the Sr2IrO4 layers can change the electron occupation of the neighboring SrTiO3 layers, which is proportional to the polarization. Via controlling the periodicity of the superlattices, we can further control the anisotropy of magnetoelectric responses. This atomic-scale design of 3d/5d superlattices paves an alternative way toward controllable magnetoelectric effects with thin film integrations.

Real-time dynamics of angular momentum transfer from spin to acoustic chiral phonon in oxide heterostructures.

Chiral phonons have recently been explored as a novel degree of freedom in quantum materials. The angular momentum carried by these quasiparticles is generated by the breaking of chiral degeneracy of phonons, owing to the chiral lattice structure or the rotational motion of ions of the material. In ferromagnets, a mechanism for generating non-equilibrium chiral phonons has been suggested, but their temporal evolution, which obeys Bose-Einstein statistics, remains unclear. Here we report the real-time dynamics of thermalized chiral phonons in an artificial superlattice composed of ferromagnetic metallic SrRuO3 and non-magnetic insulating SrTiO3. Following the photo-induced ultrafast demagnetization in the SrRuO3 layer, we observed the appearance of a magneto-optic signal in the superlattice, which is absent in the SrRuO3 single films. This magneto-optic signal exhibits thermally driven dynamic properties and a clear correlation with the thickness of the non-magnetic SrTiO3 layer, implying that it originates from thermalized chiral phonons. We use numerical calculations considering the magneto-elastic coupling in SrRuO3 to validate our experimental observations and the angular momentum transfer mechanism between the lattice and spin systems in ferromagnetic systems and also to the non-magnetic system.

Dimensionality Engineering of Magnetic Anisotropy from the Anomalous Hall Effect in Synthetic SrRuO3 Crystals.

Magnetic anisotropy in atomically thin correlated heterostructures is essential for exploring quantum magnetic phases for next-generation spintronics. Whereas previous studies have mostly focused on van der Waals systems, here we investigate the impact of dimensionality of epitaxially grown correlated oxides down to the monolayer limit on structural, magnetic, and orbital anisotropies. By designing oxide superlattices with a correlated ferromagnetic SrRuO3 and nonmagnetic SrTiO3 layers, we observed modulated ferromagnetic behavior with the change of the SrRuO3 thickness. Especially, for three-unit-cell-thick layers, we observe a significant 1500% improvement of the coercive field in the anomalous Hall effect, which cannot be solely attributed to the dimensional crossover in ferromagnetism. The atomic-scale heterostructures further reveal the systematic modulation of anisotropy for the lattice structure and orbital hybridization, explaining the enhanced magnetic anisotropy. Our findings provide valuable insights into engineering the anisotropic hybridization of synthetic magnetic crystals, offering a tunable spin order for various applications.

Impact of Cationic Stoichiometry on Physical, Optical and Electrical Properties of SrTiO3 Thin Films Grown on (001)-Oriented Si Substrates.

In this study, we investigate the changes in the crystalline structure of MBE-deposited SrTiO3 layers on Si with different deviations from Sr/Ti stoichiometry as deposited but also after annealing at high temperatures (>600 °C). We show that as-grown 15 nm thick non-stochiometric SrTiO3 layers present surprisingly lower FWHM values of the (002) omega diffraction peak compared to fully stoichiometric layers of similar thickness. This can misleadingly point to superior crystalline quality of such non-stochiometric layers. However, thermal post-deposition anneals of these layers at temperatures up to 850 °C in oxygen show strong detrimental effects on the crystalline structure, surface and interface with the Si (001) substrate. On the contrary, the post-deposition anneals applied to the stoichiometric samples strongly improve the physical, optical and electrical properties of the epitaxial SrTiO3 thin films.

Large Polarization Near 50 μC/cm2 in a Single Unit Cell Layer SrTiO3.

The generally nonpolar SrTiO3 has attracted more attention recently because of its possibly induced novel polar states and related paraelectric-ferroelectric phase transitions. By using controlled pulsed laser deposition, high-quality, ultrathin, and strained SrTiO3 layers were obtained. Here, transmission electron microscopy and theoretical simulations have unveiled highly polar states in SrTiO3 films even down to one unit cell at room temperature, which were stabilized in the PbTiO3/SrTiO3/PbTiO3 sandwich structures by in-plane tensile strain and interfacial coupling, as evidenced by large tetragonality (∼1.05), notable polar ion displacement (0.019 nm), and thus ultrahigh spontaneous polarization (up to ∼50 μC/cm2). These values are nearly comparable to those of the strong ferroelectrics as the PbZrxTi1-xO3 family. Our findings provide an effective and practical approach for integrating large strain states into oxide films and inducing polarization in nonpolar materials, which may broaden the functionality of nonpolar oxides and pave the way for the discovery of new electronic materials.

Impact of Polarity Mismatch in Infinite-Layer Nickelates.

The recent discovery of superconductivity in infinite-layer Sr-doped NdNiO2 grown on SrTiO3(001) provides a new platform to explore the conducting mechanism of unconventional superconductors. However, the electronic structure of infinite-layer nickelates remains controversial. In this paper, we systematically compare the structural and electronic properties of NdNiO2 films grown on SrTiO3 and LaAlO3 substrates using first-principles calculations. Our results show that the lattice reconstruction accompanied by electronic reconstruction occurs in nickelate films on both substrates. Although both heterostructures (HSs) are conducting at the interface, the SrTiO3-based HS shows distinct atomic displacement in the interfacial TiO2 layer and significant electron accumulation deep into three SrTiO3 layers below the interface, while the LaAlO3-based HS shows negligible atomic displacement and electron localization in the interfacial AlO2 layer, reflecting the impact of polarity mismatch on the electronic structure. Further, Wannier function calculations reveal that the interface stress has no obvious effect on the splitting energy and hopping integral between Ni 3d and Nd-layer orbitals. Although the hybridization between Ni 3dx2-y2 and Nd 5d orbitals is tiny, the hybridization between the Ni 3dx2-y2 orbital and an itinerant interstitial s (IIS) orbital is significantly strong in both cases, suggesting that the IIS orbital may play a critical role in the superconductivity of nickelates.

Reconstructing Ferroelectric Polarization Screening of PbTiO3 by Epitaxial SrTiO3 for Efficient Photocatalytic Overall Water Splitting

AbstractA large depolarization field in single‐domain PbTiO3 is anticipated to drive the spatial separation of photogenerated charge carriers and enable potential active sites for photocatalytic overall water splitting reaction. However, the negatively polarized surface usually cannot provide sufficient active sites for water oxidation to oxygen because of lacking oxygen vacancies, inevitably hindering photocatalytic water splitting reaction. Here, the ferroelectric polarization screening is reconstructed by a heteroepitaxial SrTiO3 film on the positively polarized surface of PbTiO3 nanoplates to generate abundant oxygen vacancies on the negatively polarized surface as active sites for water oxidation. Moreover, it is experimentally and theoretically revealed that the epitaxial SrTiO3 layer on the positively polarized surface is also beneficial for good dispersion of cocatalyst and the formation of low Schottky barrier height at the interface between the heterostructure and the cocatalyst for efficient electron transfer. Compared with pristine PbTiO3, the obtained PbTiO3/SrTiO3 heteroepitaxial structure with the simultaneous regulation of positively and negatively polarized surfaces delivered a greatly enhanced photocatalytic overall water splitting with stoichiometric ratio (2:1) of hydrogen and oxygen evolution by a factor of 15 times. These findings might open up a new avenue for the design of ferroelectric photocatalysts with excellent activity.

Integration of epitaxial LiNbO3 thin films with silicon technology

Development of bulk acoustic wave filters with ultra-wide pass bands and operating at high frequencies for 5th and 6th generation telecommunication applications and micro-scale actuators, energy harvesters and sensors requires lead-free piezoelectric thin films with high electromechanical coupling and compatible with Si technology. In this paper, the epitaxial growth of 36°Y-X and 30°X-Y LiNbO3 films by direct liquid injection chemical vapour deposition on Si substrates by using epitaxial SrTiO3 layers, grown by molecular beam epitaxy, has been demonstrated. The stability of the interfaces and chemical interactions between SrTiO3, LiNbO3 and Si were studied experimentally and by thermodynamical calculations. The experimental conditions for pure 36°Y-X orientation growth have been optimized. The piezoelectricity of epitaxial 36°Y-X LiNbO3/SrTiO3/Si films was confirmed by means of piezoelectric force microscopy measurements and the ferroelectric domain inversion was attained at 85 kV.cm−1 as expected for the nearly stoichiometric LiNbO3. According to the theoretical calculations, 36°Y-X LiNbO3 films on Si could offer an electromechanical coupling of 24.4% for thickness extension excitation of bulk acoustic waves and a comparable figure of merit of actuators and vibrational energy harvesters to that of standard PbZr1−x Ti x O3 films.

Effects of interfacial buffering layer on imprint and domain switching dynamics in Pb(Zr,Ti)O3 thin-film heterostructures

Interfacial engineering is important for ferroelectric thin-film heterostructures because of the modulation of boundary conditions of the spontaneous polarizations and their switching behaviors, which are essential for ferroelectric electronics. In this work, we study the effects of interfacial buffering layer, 5-nm-thick SrTiO3 (STO), on the imprint and domain switching of epitaxial Pt/Pb(Zr,Ti)O3/SrRuO3 (SRO) thin-film heterostructures and capacitors. By buffering the ultrathin SrTiO3 layer at the Pb(Zr,Ti)O3 surface, the imprint effect can be dramatically alleviated as observed in the piezoresponse force microscopy (PFM)-measured domain structures and polarization–electric field hysteresis loops in thin-film capacitors. However, when the SrTiO3 layer is buffered at the Pb(Zr,Ti)O3/SrRuO3 interface, the imprint effect is slightly increased. These phenomena are explained based on the band alignments among the Pt and SrRuO3 electrodes and the Pb(Zr,Ti)O3 layer associated with the existence of oxygen vacancies in the SrTiO3 layer. With the reduction of imprint effect, the domain switching dynamics are also improved in the SrTiO3-buffered Pb(Zr,Ti)O3 capacitor, in which the switching activation field is decreased by about 45.3% in comparison with that of the pristine capacitor. These results facilitate the design and optimization of ferroelectric devices with the improvements in domain configurations, switching behaviors and band alignments.

SrTiO3 Epitaxially Protected Si-Photocathode for Photoelectrochemical Water Splitting

Although silicon has been demonstrated to be one of the best photoelectrochemical (PEC) substrate materials thanks to its low cost, mature manufacturing technique, and high theoretical photovoltage and saturation current density [1], the development of robust Si-based PEC device has remained an existing challenge due to the fact that it is very easily susceptible to (photo)corrosion under PEC operational conditions [2]. Therefore, a suitable protective layer over the Si substrate which is able to simultaneously provide the corrosion resistance and retain a highly efficient charge transfer across the photoelectrode device is highly desired [3].To this end, we prepared high-quality SrTiO3 (STO) layer to passivate p-Si substrate via the mediation of an epitaxial enabler reduced graphene oxide (rGO) using the pulsed laser deposition (PLD) technique. STO layers with different thicknesses were prepared on both rGO-buffered and bare Si substrates to investigate the effects of epitaxy and charge carrier migration distance on the PEC performance. It was realized that very thin (3.9 nm ~ 10 unit cells) STO layer epitaxially overgrown on rGO-buffered Si showed the highest onset potential (0.326 V vs RHE, defined as potential at -0.1 mA cm-2) than the counterparts with thicker and/or non-epitaxial STO. The photovoltage and flat-band potential analyses, and the electrochemical impedance spectroscopy measurements showed that the epitaxial protected photocathode was more beneficial for charge separation, charge transfer, and the targeted redox reaction (hydrogen evolution reaction in this case) than the non-epitaxial one. The STO/rGO/Si with a smooth and highly epitaxial STO layer outperforming the direct contacted STO/Si with textured and polycrystalline STO layer underscored the importance of having well-defined passivation layer. In addition to that, numerous pinholes formed in STO/Si attributable to highly energetic bombardment process in the PLD deposition led to a rapid degradation of photocathode during PEC measurements, possibly because the electrolyte could easily penetrate into the film and consequently corrode the substrate. Single-oriented STO realized by rGO-buffered substrate potentially rendered easier path for charge migration, and the thinnest STO layer provided the shortest transportation route while maintained the robust protection ability. Polycrystalline STO in direct contacted STO/Si however presented more recombination sites which eventually impaired the PEC performance. Smooth surface of high-quality epitaxial STO layer with sub-nano roughness demonstrated to be a pivotal factor in remotely protecting underlying p-Si substrate from corrosion, while the presence of pinholes in non-epitaxial sample showed a similar degradation rate as bare Si substrate which was without any protection. We also studied the capability of STO layer in protecting underlying Si substrate from corrosion, and the long-term stability tests demonstrated the robustness of epitaxial STO layer-coated photocathode in comparison to bare Si.We demonstrated that STO layer overgrown on Si buffered with few-layer epitaxy enabler rGO could promote charge carrier transfer across the photocathode and lead to better PEC performance. Through a series of in-situ and ex-situ characterizations we verified that the addition of rGO layer could significantly alter the STO layer crystallinity and thin film morphology and, most importantly, enhance the stability of Si photocathode with only 10 unit cells layer. This study reported a facile approach for preparing a robust protection layer over photoelectrode substrate in realizing efficient and at the same time durable PEC device. Acknowledgement: This study was supported by Slovenian Research Agency (Project No. N2-0187) and the Czech Science Foundation (Project No. 21-20110K). We also thank the supports from Mr. Damjan Vengust in electron microscope observations, Mr. Jožko Fišer in Pt thin film preparation, Dr. Vasko Jovanovski in discussion of electrochemical measurements.

Synthesis of BaTiO3-CaTiO3 and BaTiO3-SrTiO3 Core-Shell Nanocubes via the Surface Reconstruction of BaTiO3 Nanocubes.

BaTiO3-CaTiO3 and SrTiO3-BaTiO3 core-shell nanocubes were synthesized through the surface reconstruction of BaTiO3 nanocubes, which involved the reaction of titanium oxide with Ca(OH)2, Sr(OH)2, or Sr(OH)2·8H2O in water at 100 °C. The core-shell structure comprised a BaTiO3 nanocube core and a CaTiO3 or SrTiO3 shell. The outermost layer with a perovskite structure also comprised CaTiO3 or SrTiO3, and its thickness was several hundred picometers. The thinnest layer was constructed of only one layer of CaTiO3 or SrTiO3. This is the first presented work on a core-shell nanocube with the outermost layer consisting of only CaTiO3 or SrTiO3 surrounding the BaTiO3 nanocube. The shells of CaTiO3 and SrTiO3 comprise a layer thickness of only one unit cell of ∼0.4 nm (400 pm). Thus, we demonstrate new research on nanocube surfaces on the picometer scale.

Robust SrTiO3 Passivation of Silicon Photocathode by Reduced Graphene Oxide for Solar Water Splitting.

Development of a robust photocathode using low-cost and high-performing materials, e.g., p-Si, to produce clean fuel hydrogen has remained challenging since the semiconductor substrate is easily susceptible to (photo)corrosion under photoelectrochemical (PEC) operational conditions. A protective layer over the substrate to simultaneously provide corrosion resistance and maintain efficient charge transfer across the device is therefore needed. To this end, in the present work, we utilized pulsed laser deposition (PLD) to prepare a high-quality SrTiO3 (STO) layer to passivate the p-Si substrate using a buffer layer of reduced graphene oxide (rGO). Specifically, a very thin (3.9 nm ∼10 unit cells) STO layer epitaxially overgrown on rGO-buffered Si showed the highest onset potential (0.326 V vs RHE) in comparison to the counterparts with thicker and/or nonepitaxial STO. The photovoltage, flat-band potential, and electrochemical impedance spectroscopy measurements revealed that the epitaxial photocathode was more beneficial for charge separation, charge transfer, and targeted redox reaction than the nonepitaxial one. The STO/rGO/Si with a smooth and highly epitaxial STO layer outperforming the directly contacted STO/Si with a textured and polycrystalline STO layer showed the importance of having a well-defined passivation layer. In addition, the numerous pinholes formed in the directly contacted STO/Si led to the rapid degradation of the photocathode during the PEC measurements. The stability tests demonstrated the soundness of the epitaxial STO layer in passivating Si against corrosion. This study provided a facile approach for preparing a robust protection layer over a photoelectrode substrate in realizing an efficient and, at the same time, durable PEC device.

Photoactive Properties of Transport Sol-Gel Layers Based on Strontium Titanate for Perovskite Solar Cells

In this work, we have investigated the photocurrent and spectral sensitivity of the silicon/SrTiO3:xNb/perovskite structures. The sol–gel method carried out the deposition of undoped SrTiO3 layers as well as niobium-doped (SrTiO3:Nb) layers at atomic concentrations of 3 and 6% Nb. The perovskite layer, CH3NH3PbI3−xClx, has been deposited by the vacuum co-evaporation technique. The layers have been characterized by scanning electron microscopy and X-ray diffraction measurements. The volt–ampere characteristics and spectral sensitivity of the fabricated samples have been measured under illumination with selective wavelengths of 405, 450, 520, 660, 780, 808, 905, 980, and 1064 nm of laser diodes. We have shown that for different configurations of applied voltage between silicon, SrTiO3:xNb, and CH3NH3PbI3−xClx, the structures are photosensitive ones with a variation of photocurrent from microamperes to milliamperes depending on Nb concentration in SrTiO3, and the highest photocurrent and spectral sensitivity values are observed when a SrTiO3:Nb layer with 3 at.% of Nb is used. A possible application of the proposed structure with a SrTiO3:Nb layer for perovskite solar cells and photodetectors is being discussed.

Impact of surface preparation on the epitaxial growth of SrTiO3 on ScAlN/GaN heterostructures

Heterogeneous integration of functional oxides with ultra-wide bandgap (UWBG) semiconductors is desired for the realization of novel hybrid systems applicable to a wide array of commercial electronics and defense applications. In this work, we demonstrate the growth of crystalline SrTiO3 (STO) thin films on high-electron-mobility transistor (HEMT) heterostructures based on an emergent UWBG semiconductor ScAlN, used as the barrier layer on a GaN channel, and determine the effects of the pre-growth chemical treatments of the ScAlN surface on resultant heterostructure properties. We investigate wet chemical cleans of ScAlN with solvents, piranha solution, UV ozone and hydrofluoric acid, and a sulfuric-phosphoric acid mix prior to STO growth, and show that the commonly used piranha solution degrades the ScAlN surface, thereby reducing the crystal quality of the deposited STO layers and lowering the channel mobility. We determine that among the treatments studied, the solvent and sulfuric-phosphoric acid cleans were the least disruptive to the electrical properties of the GaN channel as evidenced from Hall effect measurements, but the sulfuric-phosphoric acid clean results in best oxide crystallinity, as determined from structural characterizations. We perform transmission electron microscopy imaging on the piranha-treated and sulfuric-phosphoric-treated samples to compare the microstructure and find that while intermixing occurs at the oxide-nitride interfaces for both samples, the interface roughness is lower and the STO grain size is larger in the sample with sulfuric-phosphoric acid treatment. This work demonstrates the first epitaxial growth of STO on an UWBG semiconductor and motivates STO/ScAlN/GaN as material platforms for high-frequency, high-power-density HEMTs.

Electric-field control of reversible electronic and magnetic transitions in two-dimensional oxide monolayer magnets

Atomically thin oxide magnetic materials are highly desirable due to the promising potential to integrate two-dimensional (2D) magnets into next-generation spintronics. Therefore, 2D oxide magnetism is expected to be effectively tuned by the magnetic and electrical fields, holding prospective for future low-dissipation electronic devices. However, the electric-field control of 2D oxide monolayer magnetism has rarely been reported. Here, we present the realization of 2D monolayer magnetism in oxide (SrRuO3)1/(SrTiO3)N (N = 1, 3) superlattices that shows an efficient and reversible phase transition through electric-field controlled proton (H+) evolution. By using ionic liquid gating to modulate the proton concentration in (SrRuO3)1/(SrTiO3)1 superlattice, an electric-field induced metal-insulator transition was observed, along with gradually suppressed magnetic ordering and modulated magnetic anisotropy. Theoretical analysis reveals that proton intercalation plays a crucial role in both electronic and magnetic phase transitions. Strikingly, SrTiO3 layers can act as a proton sieve, which have a significant influence on proton evolution. Our work stimulates the tuning functionality of 2D oxide monolayer magnetism by voltage control, providing potential for future energy-efficient electronics.

Dendrite-Free Zinc Deposition Induced by an Artificial Layer of Strontium Titanate for Stable Zinc Metal Anode

Rechargeable aqueous zinc ion batteries, featuring as high specific capacity, low cost and high safety, are considered one of the most promising alternatives to lithium-ion batteries for the next-generation energy storage system. Nevertheless, the undesired dendrite formation and serious side reaction of Zn metal anode significantly hinder the usage of Zn-based metal batteries. Here, we propose a nanosized SrTiO3 film as a highly self-adapting protective coating to facilitate fast Zn2+ kinetics and guarantee even ion flux, leading to endow homogeneous Zn deposition under the SrTiO3 layer. Consequently, the symmetric batteries equipped with SrTiO3-coated Zn electrodes obtain a long-term cycling lifespan for 1000h with a fixed capacity of 1 mA h cm−2 without the formation of zinc dendrites. Furthermore, the Zn@SrTiO3||MnO2 full battery displays excellent cycling stability and rate performance. This study emphasizes the important role of SrTiO3 layer in designing the interfacial stability during zinc redox process for stable aqueous Zn metal batteries.

Emergent Phenomena in KTaO3/SrTiO3 Heterostructure

KTaO3 has become a new material of attraction for exploring various exotic properties at its surface and interfaces. To explore the substrate effect of KTaO3, we have studied a new heterostructure made by KTaO3 and SrTiO3. KTaO3 is a 5d polar perovskite with the complementary planes of KO− and , whereas SrTiO3 is a 3d non-polar perovskite with alternative stacking SrO0 and . By taking the epitaxial layers of SrTiO3 on top of KTaO3, we have created two different interfaces along (0 0 1), which are and . We have studied these two interfaces by using density functional theory. In interface, the signature of two-dimensional hole gas (2DHG) has been found. Though the interface turns to insulator when epitaxial layers reach beyond 4.5 u.c. The other one, i.e., interface, shows the typical behaviour of two-dimensional electron gas (2DEG), only at the epitaxial layer 2.5 uc. The presence of both types of carriers in a single system for different kinds of interfaces has great use in various device applications.

The Effect of Oxygen Vacancies on the Diffusion Characteristics of Zn(II) Ions in the Perovskite SrTiO3 Layer: A Computational Study.

A highly polar perovskite SrTiO3 (STO) layer is considered as one of the promising artificial protective layers for the Zn metal anode of aqueous zinc-ion batteries (AZIBs). Although it has been reported that oxygen vacancies tend to promote Zn(II) ion migration in the STO layer and thereby effectively suppress Zn dendrite growth, there is still a lack of a basic understanding of the quantitative effects of oxygen vacancies on the diffusion characteristics of Zn(II) ions. In this regard, we comprehensively studied the structural features of charge imbalances caused by oxygen vacancies and how these charge imbalances affect the diffusion dynamics of Zn(II) ions by utilizing density functional theory and molecular dynamics simulations. It was found that the charge imbalances are typically localized close to vacancy sites and those Ti atoms that are closest to them, whereas differential charge densities close to Sr atoms are essentially non-existent. We also demonstrated that there is virtually no difference in structural stability between the different locations of oxygen vacancies by analyzing the electronic total energies of STO crystals with the different vacancy locations. As a result, although the structural aspects of charge distribution strongly rely on the relative vacancy locations within the STO crystal, Zn(II) diffusion characteristics stay almost consistent with changing vacancy locations. No preference for vacancy locations causes isotropic Zn(II) ion transport inside the STO layer, which subsequently inhibits the formation of Zn dendrites. Due to the promoted dynamics of Zn(II) ions induced by charge imbalance near the oxygen vacancies, the Zn(II) ion diffusivity in the STO layer monotonously increases with the increasing vacancy concentration ranging from 0% to 16%. However, the growth rate of Zn(II) ion diffusivity tends to slow down at relatively high vacancy concentrations as the imbalance points become saturated across the entire STO domain. The atomic-level understanding of the characteristics of Zn(II) ion diffusion demonstrated in this study is expected to contribute to developing new long-life anode systems for AZIBs.

Strained BaTiO3 thin films via in-situ crystallization using atomic layer deposition on SrTiO3 substrate

The interface engineering of oxide heterostructures, such as BaTiO3 (BTO)/SrTiO3 (STO), has received considerable attention because of their interesting physical/electrical properties. In this study, the in-situ crystallization of BTO thin film was achieved using a high temperature (∼350 °C) atomic layer deposition (ALD) process, which enabled the formation of strained BTO thin films on the STO substrate. A compressive strain was introduced along the in-plane direction of the BTO film, resulting in a 1.5% decrease in the lattice constant of BTO film while an in-plane tensile strain was induced in the STO layer (0.8% increase in the lattice constant). The in-situ crystallization of BTO thin films grown by ALD allowed the formation of a strained interface at the BTO/STO heterostructure.

Promoting Zn2+ migration through polar perovskite dielectric layer on Zn metal anode for the enhanced aqueous Zn-ion batteries

Aqueous zinc-ion batteries (AZIBs) have gained significant attention as promising next-generation energy storage systems owing to their prominent features such as low cost, environmental friendliness, high theoretical capacity (819 mAh g−1 and 5849 mAh cm−2), and low redox potential (−0.762 V vs. standard hydrogen evolution). However, several challenges to Zn metal anodes, such as uncontrollable dendritic growth, hydrogen evolution, and corrosion reactions in water-based electrolytes, result in unstable and poorly reversible electrochemical performance. Herein, we demonstrate a highly polar perovskite SrTiO3 (STO) layer introduced on Zn metal as an artificial layer promotes Zn2+ migration and suppresses the random dendrite growth in the mild aqueous electrolyte. STO-coated Zn anode (STO@Zn) highly improves the reversibility of electrochemical reaction in a symmetrically configured cell relative to bare Zn, with a significantly lower overpotential of 4000 h. Various electrochemical characterizations show uniform and rapid Zn2+ transport via the artificial STO layer. A full-cell test with VO2 cathode confirmed the excellent properties of STO@Zn, demonstrating reversible and stable performance with long service life. This study presents new insights into the design and development of promising Zn metal anodes for next-generation energy storage systems.