SrTiO3 Films Research Articles

Amorphous Exsolution of Fe3O4 Nanoparticles in SrTiO3: A Path to High Activity and Stability in Photoelectrochemical Water‐Splitting

Exsolution creates metal nanoparticles embedded within perovskite oxide matrices, promoting optimal exposure, even distribution, and robust interactions with the perovskite structure. Fe3O4, an oxidized form of Fe, is an attractive catalyst for photoelectrochemical (PEC) water‐splitting due to its strong light absorption, excellent electrical conductivity, and chemical stability. However, exsolving Fe is challenging, often requiring harsh reduction conditions that can decompose the perovskite. Herein, hybrid composites are fabricated for PEC water‐splitting by reductively annealing a solution of SrTiO3 photoanode and Fe cocatalyst precursors. In situ transmission electron microscopy reveals uniform, high‐density Fe particles exsolving from amorphous SrTiO3 films, followed by film‐crystallization at elevated temperatures. This innovative process extracts entire Fe dopants while maintaining structural stability, even at doping levels exceeding 50%. Upon air exposure, the embedded Fe particles oxidize to Fe3O4, forming a Schottky junction and enhancing light absorption. These conditions yield a high activity of 5.10 mA cm−2 at 1.23 V versus reversible hydrogen electrode (an 11.86‐fold improvement over SrTiO3) from the 30% Fe‐doped SrTiO3, with excellent stability (97% retention) over 24 h. Theoretical calculations indicate that in the amorphous state, FeO bonds weaken while TiO bonds remain strong, promoting selective exsolution. The mechanisms driving amorphous exsolution versus crystal exsolution are elucidated.

Enhanced Crystallinity of SrTiO3 Films on a Silicon Carbide Substrate: Structural and Microwave Characterization

Thin films of strontium titanate, which reveal high structure quality and tunable properties prospective for microwave applications at room temperature, were grown on a semi-insulating silicon carbide substrate using magnetron sputtering for the first time. The films’ growth mechanisms were studied using medium-energy ion scattering, and the films’ structures were investigated using X-ray diffraction. The electrical characteristics of planar capacitors based on strontium titanate films were measured at a frequency of 2 GHz using a high-precision resonance technique. It is shown that the tendency to improve the crystalline structure of strontium titanate film with an increase in the substrate temperature is most pronounced for films deposited at elevated working gas pressure under low supersaturation conditions. Planar capacitors formed on the basis of oriented SrTiO3 films on silicon carbide showed tunability n = 36%, with a loss tangent of 0.008–0.009 at a level of slow relaxation of capacitance, which is significantly lower than the data published currently regarding planar tunable ferroelectric elements. This is the first successful attempt to realize a planar SrTiO3 capacitor on a silicon carbide substrate, which exhibits a commutation quality factor more than 2500 at microwaves.

Superior energy storage performance in lead-free SrTiO3 films via ion doping and crystalline optimization

SrTiO3 paraelectric materials exhibit significant potential to be used as lead-free energy storage dielectrics due to their distinctive linear-like polarization behavior. Nonetheless, the application in advanced thin-film capacitors is challenging due to their low polarization strength and structural anomalies, which reduce the breakdown field strength and diminish the energy storage density. This study proposes a synergistic approach that integrates ion doping with the optimization of thermal treatment to enhance the energy storage capabilities of SrTiO3 thin films. Initially, Mn2+ doping in SrTiO3 films mitigates oxygen vacancies and forms Mn2+-VO•• defect dipoles, thereby refining the polarization behavior and reducing the leakage current density. Subsequently, the crystalline degree of SrTi0.99Mn0.01O3 thin films can be regulated by adjusting the annealing temperature. The optimal breakdown field strength of the resultant SrTi0.99Mn0.01O3 films reaches 4681 kV/cm with a 1 mol% Mn2+ doping level, enhancing the recoverable energy storage density (Wrec) to 32.17 J/cm3. Furthermore, the recoverable energy storage density of SrTi0.99Mn0.01O3 films escalates to 36.62 J/cm3 with an efficiency of 80.28 %, upon reducing the annealing temperature to 625 °C. Moreover, SrTi0.99Mn0.01O3 films demonstrate superior thermal stability, frequency stability, and electrical fatigue resistance, underscoring their potential as efficacious materials for film capacitor applications.

All Oxide-Based Magnetic Tunnel Junctions Fabricated by Focused Ion Beam Nanomachining Technique

This study offers a comprehensive investigation into the fabrication of all-oxide-based magnetic tunnel junctions (MTJs) utilizing the focused ion beam (FIB) nanomachining method. The oxide thin films of SrTiO3 (STO), La[Formula: see text]CaxMnO3 (LCMO) and La[Formula: see text]SrxMnO3 (LSMO) were grown using pulsed laser deposition (PLD). Magnetization measurements at 5K revealed a notable difference in coercivity between LCMO and LSMO films, highlighting their suitability as electrodes in MTJ device fabrication. The deposited trilayer structure of LCMO/STO/LSMO exhibited heteroepitaxial growth, enabling the independent magnetic switching of electrode layers in the MTJ with the STO barrier layer. Conventional photolithography and ion milling were used to create a series of 4[Formula: see text][Formula: see text]m Hall bar tracks in the deposited films. Nanopillar devices, sized 250[Formula: see text]nm[Formula: see text]×[Formula: see text]250[Formula: see text]nm, were successfully fabricated on these 4[Formula: see text][Formula: see text]m tracks by optimizing the FIB nanomachining technique. The fabricated MTJs demonstrated a high tunnel magnetoresistance (TMR) response, leading to the conclusion that the FIB nanomachining technique holds significant promise for the development of high-performance oxide-based spintronic devices.

Electrical and surface properties of chemically deposited SrTiO3 films on ITO/glass substrate

In the present communication, for understanding the properties of thickness dependent STO/ITO thin films, the films were prepared using sol–gel sputtering technique wherein, different STO thickness are grown over ITO substrate. The structural properties understood using the XRD patterns wherein, observation shows the presence of amorphous STO without any detectable impurities. The Microstructural and cross-section analysis gives insight information of the films with batter distribution of grain and upper portion (STO) and lower portion (ITO) respectively which gets modifies with different thicknesses. The elemental composition of the studied films observed using EDAX and XPS spectrum reveals the only presence of required material with homogeneous distribution of all elements. From the a.c. conductivity and impedance spectroscopy the electrical properties of the films were measured wherein, for understanding the insight information’s the theoretical model such as; Jonscher’s power law, and Nyquist plot were fitted. The alternation of the properties can be studied using grain, grain boundaries, thickness of the film and different derived parameters.

Effect of Cupric-Doped SrTiO3 Films on Optical Properties Using Spectrophotometry Method

Effect of Cupric-Doped SrTiO3 Films on Optical Properties Using Spectrophotometry Method

Low temperature crystallization of atomic-layer-deposited SrTiO3 films with an extremely low equivalent oxide thickness of sub-0.4 nm

Despite SrTiO3(STO) possessing a high dielectric constant, its application as a capacitor dielectric in dynamic random-access memory(DRAM) capacitors faces challenges due to the high-temperature annealing for crystallization, its compositional inhomogeneity, and the high leakage currents of STO films. To address these issues, we employ atomic layer deposition(ALD) of STO films onto Pt substrates at elevated temperatures(340–380 °C). The use of low-reactivity Pt electrodes effectively mitigates the initial growth of excess Sr, ensuring enhanced compositional uniformity along the film growth direction. Coupled with ALD at high temperatures, this approach facilitates the crystallization of STO films in the as-grown state, further enhancing the crystallinity with increasing film thickness. Subsequent low-temperature post-deposition annealing (PDA) at 400 and 500 °C achieves full crystallization. This process results in a remarkable increase in the dielectric constant, reaching approximately 150. Furthermore, the absence of microcracks after PDA, attributed to the formation of adequately dense films, contributes to substantially improved dielectric properties. Consequently, these STO films exhibit an exceptionally low equivalent oxide thickness of 0.34 nm coupled with an ultralow leakage current of 3.7 × 10−8 A/cm2 at an operation voltage of 0.8 V, promising for advancing DRAM capacitors. This study presents a pathway for the sustainable scaling of DRAMs, addressing challenges in ALD-grown STO 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.

Study on field emission performance of SrTiO3 film enhanced by LiF film

A series of monolayer SrTiO3 films and LiF/SrTiO3 bilayer films were prepared on n-Si substrates by using vacuum electron beam vapor deposition (EBVD) technology. The morphologies and thicknesses of the SrTiO3 film and LiF film were controlled through adjustments and optimization of the growth conditions as well as deposition time. The experimental results show that the field emission performance of SrTiO3 film is significantly improved after LiF film is added. Under the research conditions in our laboratory, a large number of LiF/SrTiO3 bilayer film field emission devices have been tested and analyzed in the wide range of LiF film thickness (10–300 nm), and the effective field emission LiF film thickness (50–90 nm) was initially determined. Further study shows that the LiF/SrTiO3 bilayer film has the best field emission performance when the optimal LiF film thickness is 70 nm, and its maximum field emission current density can reach 305.48 μA/cm2. The field emission current density of the LiF/SrTiO3 bilayer thin film device is nearly 4 times compared to that of the monolayer SrTiO3 film when the applied electric field intensity reaches 9.05 V/μm. All the field emission devices exhibit excellent functioning stability and experimental reproducibility.

Highly reversible extrinsic electrocaloric effects over a wide temperature range in epitaxially strained SrTiO3 films

Electrocaloric effects have been experimentally studied in ferroelectrics and incipient ferroelectrics, but not incipient ferroelectrics driven ferroelectric using strain. Here we use optimally oriented interdigitated surface electrodes to investigate extrinsic electrocaloric effects in low-loss epitaxial SrTiO3 films near the broad second-order 243 K ferroelectric phase transition created by biaxial in-plane coherent tensile strain from DyScO3 substrates. Our extrinsic electrocaloric effects are an order of magnitude larger than the corresponding effects in bulk SrTiO3 over a wide range of temperatures including room temperature, and unlike electrocaloric effects associated with first-order transitions they are highly reversible in unipolar applied fields. Additionally, the canonical Landau description for strained SrTiO3 films works well if we set the low-temperature zero-field polarization along one of the in-plane pseudocubic <100> directions. In future, similar strain engineering could be exploited for other films, multilayers and bulk samples to increase the range of electrocaloric materials for energy efficient cooling.

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.

Nature of the metallic and in-gap states in Ni-doped SrTiO3

Epitaxial thin films of SrTiO3(100) doped with 6% and 12% Ni are studied with resonant angle-resolved photoelectron spectroscopy at the Ti and Ni L2,3-edges. We find that the Ni doping shifts the valence band of n-doped pristine SrTiO3 toward the Fermi level (in the direction of p-doping) and reducing the bandgap. In the Ti t2g-derived mobile electron system (MES), the Ni doping depopulates the out-of-plane dxz/yz-derived bands, transforming the MES to two-dimensional and progressively reduces the electron density embedded in the in-plane dxy-derived bands as reflected in their Fermi momentum. Furthermore, the Ti and Ni L2,3-edge resonant photoemission is used to identify the Ni 3d impurity state in the vicinity of the valence-band maximum and decipher the full spectrum of the in-gap states originating from the Ni atoms, Ti atoms, and from their hybridized orbitals. Our experimental information about the dependence of the valence bands, MES, and in-gap states in Ni-doped SrTiO3 may help the development of this material toward its device applications associated with the reduced optical bandgap.

Maximizing Photoelectrochemical Performance in Metal-Oxide Hybrid Composites via Amorphous Exsolution-A New Exsolution Mechanism for Heterogeneous Catalysis.

Exsolution generates metal nanoparticles anchored within crystalline oxide supports, ensuring efficient exposure, uniform dispersion, and strong nanoparticle-perovskite interactions. Increased doping level in the perovskite is essential for further enhancing performance in renewable energy applications; however, this is constrained by limited surface exsolution, structural instability, and sluggish charge transfer. Here, hybrid composites are fabricated by vacuum-annealing a solution containing SrTiO3 photoanode and Co cocatalyst precursors for photoelectrochemical water-splitting. In situ transmission electron microscopy identifies uniform, high-density Co particles exsolving from amorphous SrTiO3 films, followed by film-crystallization at elevated temperatures. This unique process extracts entire Co dopants with complete structural stability, even at Co doping levels exceeding 30%, and upon air exposure, the Co particles embedded in the film oxidize to CoO, forming a Schottky junction at the interface. These conditions maximize photoelectrochemical activity and stability, surpassing those achieved by Co post-deposition and Co exsolution from crystalline oxides. Theoretical calculations demonstrate in the amorphous state, dopant─O bonds become weaker while Ti─O bonds remain strong, promoting selective exsolution. As expected from the calculations, nearly all of the 30% Fe dopants exsolve from SrTiO3 in an H2 environment, despite the strong Fe─O bond's low exsolution tendency. These analyses unravel the mechanisms driving the amorphous exsolution.

The Blood Hemoglobin Sensor Based On (Ba,Sr)TiO3 Films: The Performance Evaluation and Data Analysis

The information of blood hemoglobin level is very important for human health. Normal hemoglobin levels for men are in the range of 14-18.5 g/dL, and for women in the range of 12-16.5 g/dL. A hemoglobin level below the normal range indicates an anemia problem which could be fatal for human’s health. To detect the blood hemoglobin level, optical sensors must respond to the light within the range of 250-900 nm wavelength. In this paper we report the performance of Barium Titanate and Strontium Titanate (Ba,Sr)TiO3 films which are capable of detecting the blood hemoglobin level in the spectrum range of 380-780 nm. The performance of (Ba,Sr)TiO3 then compared with FDS100 standard sensor. The LED in this study, as a light source, has a wavelength of 545 nm and 570 nm. The (Ba,Sr)TiO3 film, LED and artificial blood samples were placed in a container and integrated with other electronic devices. The hemoglobin (Ba,Sr)TiO3 measurement data obtained was then processed using a machine learning method (linear regresion algorithm) and compared with the actual hemoglobin value from artificial blood. The evaluation of data measurement using linear regresion showed that BaTiO3 has more accuracy (84.83%) as compared to SrTiO3 (82.95%). This result is in accordance with the result from the optical and electrical properties, where a small band gap energy and a small resistance produce better optical and electrical properties resulting in a higher level of accuracy.

Using a perovskite oxide buffer layer on Ca2Nb3O10 nanosheets for the epitaxial growth of Pb(Zr0.52Ti0.48)O3 for electrode-free thin films

Ca2Nb3O10 nanosheet layers were deposited on Gallium Nitride (GaN)-on-Si substrates by the Langmuir-Blodgett method to obtain (001)-oriented growth of perovskite oxide thin films using pulsed laser deposition. We investigated the influence of 10 nm thick SrTiO3, (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) and LaMnO3 films as buffer layers on the structural and ferroelectric properties of subsequentially grown Pb(Zr0.52Ti0.48)O3 (PZT) films, which may be used as gate capacitors in high power GaN devices. Scanning Electron Microscopy, Atomic Force Microscopy, X-Ray-Diffraction and in-plane polarization experiments were used to determine the influence of the oxide buffer layers on the PZT properties. Highly crystalline dense (001)-oriented PZT films with large in-plane polarizations were obtained using SrTiO3 and LSAT as buffer layers. For SrTiO3 and LSAT we observed an improvement of the structural and ferroelectric properties compared to PZT grown directly on the Ca2Nb3O10 nanosheets and or using a LaMnO3 buffer layer. The improved high-crystallinity PZT films grown on GaN using ultrathin buffer layers could enhance the performance of high-power semiconductor electronics or in other devices where there is a need for a ferroelectric layer without bottom electrode.

SrTiO3 Thin Films on Dielectric Substrates for Microwave Applications

Thin films of strontium titanate, which have nonlinear properties that are promising for microwave applications, were grown on a polycrystalline aluminum oxide substrate using magnetron sputtering and high-temperature annealing. It was shown that the improvement of the film structure with an increase in the deposition temperature was clearly correlated with both an increase in nonlinearity and an improvement in the loss level. A capacitor based on an SrTiO3 film deposited at a deposition temperature of 900 °C and subjected to annealing demonstrated a tunability of 46% with a loss tangent of 0.009–0.014 at a frequency of 2 GHz. This was the first successful attempt to form a planar SrTiO3 capacitor on an alumina substrate, which exhibited a commutation quality factor of above 3000 in the microwave range.

Near-Ultraviolet Lateral Photovoltaic Effect of Epitaxial Nb:SrTiO3 Films on Si Substrate Using TiN as a Buffer Layer

Near-Ultraviolet Lateral Photovoltaic Effect of Epitaxial Nb:SrTiO3 Films on Si Substrate Using TiN as a Buffer Layer

Photocatalytic degradation of hazard migrated compound from food packaging materials using antimicrobial strontium titanate incorporated cellulose acetate

Packaging food safety is a stone corner in fresh food's production and its commercialization process. Recently, researchers studied the hazardous (detection and determination) of migrated compounds from printed packaging film. A new direction in wastewater treatment of hazardous migratory substances in food packaging is urgently needed. Cellulose acetate (CA) and strontium titanate (SrTiO3) were prepared to accelerate the photocatalytic degradation of print waste material. The prepared films contained different percentages of SrTiO3 (ST) (10, 5, 2.5 and zero % (wt/wt)). The characterizations of prepared cellulose acetate/ SrTiO3 films (CA/ST) were investigated using ATR-FTIR, SEM, EDX, XRD, UV and BET. The photocatalytic degradation study observed that 10 % strontium titanate/cellulose acetate affirmed the excellent where catalytic degradation was carried out in a shorter time (60 min). The reusability of all films was assigned five times with approximately the same efficiency. The antimicrobial activity of the CA/ST films against the most infectious contaminated microorganisms emphasizes that the prepared films can be described as broad-spectrum antimicrobial agents. The dual rule of prepared films as photocatalyst and antimicrobial agents give a great advantage to safe water from agri-food plastic transparent printed packaging.

Single-layer SrTiO3 film and SiO2/SrTiO3 composite film white electroluminescence performance comparison

Single-layer SrTiO3 film and SiO2/SrTiO3 composite film electroluminescence (EL) devices were fabricated on n-Si substrate though vacuum electron vapor deposition (EBVD) technique. The film layers in the device were analyzed using various detection methods to determine their microstructure and composition, and the EL properties of both types of devices were compared. EL experimental results show that both devices can emit white light visible to the naked eye when the forward bias is applied. Moreover luminescence intensity of SiO2/SrTiO3 composite thin film devices is much higher than that of single-layer SrTiO3 thin film devices. The EL spectrum analysis of the device samples shows that there are three luminescence peaks in both types of devices, and they are located in the blue, yellow and red regions. Three emission peaks of single-layer SrTiO3 thin film devices are located at 460 nm (blue region), 580 nm (yellow region) and 685 nm (red region). Three luminescence peaks of SiO2/SrTiO3 composite thin film devices are located at 460 nm (blue region), 585 nm (yellow region) and 716 nm (red region). In composite film devices, SiO2 acts as an electron barrier layer, confining electrons to the SrTiO3 film layer and increasing the chance for the electrons in the SrTiO3 conduction band to participate in the composite luminescence. As a result, the blue peak emission intensity of the SrTiO3 composite film device is significantly enhanced, while the overall white light emission intensity of the composite thin film device is greatly improved. Additionally, the color coordinates of SiO2/SrTiO3 composite film device is closer to those of standard white light according to CIE standards.

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.