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Flexible ferroelectric memories, endowing with high data storage density, provide a chance for the next-generation wearable electronics. Here, flexible inorganic Mn-doped BiFeO3 thin films were directly integrated on fluorophlogopite mica (F-Mica) substrates by an easy and low-cost all solution chemical solution deposition (AS-CSD) route. The integration of LaNiO3 buffer layer can improve the film surface density and uniformity. The flexible characteristic can be achieved by reducing the thickness of F-Mica substrates for the ferroelectric thin films. In contrast to BiFe0·93Mn0·07O3/LaNiO3/Si thin film deposited on rigid substrates (Si), the BiFe0·93Mn0·07O3/LaNiO3/F-mica fabricated on F-Mica show better ferroelectric performances due to the improved crystal growth and less defects. More importantly, the obtained BiFe0·93Mn0·07O3/LaNiO3/F-mica ferroelectric thin films still show large remnant polarization of Pr ∼64 μC/cm2 (deterioration of ∼7.2%), good antifatigue properties up to 1.2 × 108 cycles and outstanding retention behaviors for 1.6 × 104 s after continuous bending. This work will provide a feasible route to fabricate flexible inorganic ferroelectric thin films through low-cost solution method and show attractive comprehensive performances in next-generation wearable smart devices.

A backward diode consisting of all nondegenerate and transparent semiconducting oxides (TSOs) offers promising opportunities for designing multifunctional electronic devices. In this letter, we report the backward diode rectifying behavior in the nondegenerate AgCrO2/In2O3 p-n heterojunction. Both AgCrO2 and In2O3 films are transparent. The decrease of grain boundary in the In2O3 film can improve the backward diode rectifying performance. The optimized AgCrO2/In2O3 heterojunction exhibits a very high reverse rectification ratio that exceeds 103 along with a small tunneling current onset voltage. The backward diode rectifying behavior originates from the electron band-to-band tunneling (BTBT) current in the reverse voltage region, which is induced by type-III band alignment. This study will pave the way for achieving transparent backward diodes by using all nondegenerate TSOs p-n heterojunctions.

Transparent conducting (TC) donor-doped In2O3 thin films are the critical components in photovoltaic, display and solid-state lighting fields. In2O3-based TC films with high carrier mobility are required for reducing the power consumption of devices. Meanwhile, a high near-infrared (NIR) transparency can significantly improve the power conversion efficiency in solar cells. Here, W-doped In2O3 thin films with high carrier mobility and NIR transparency were obtained through a facile solution process, which is suitable for large-scale thin film fabrication. The effects of W concentration (0.3 at% to 0.7 at%) on the microstructures, electrical and optical properties of In2O3 thin films are investigated in detail. It is found that the 0.5% W-doped In2O3 thin film exhibits high carrier mobility of 23 cm2 V−1 s−1 at a carrier concentration of 5.02 × 1020 cm−3, showing a high NIR transmittance over 82% and low sheet resistance of 32 Ω/sq. The solution processed W-doped In2O3 thin films with low sheet resistance and high NIR transparency can be potentially used as transparent electrodes for solar cells.

Pure chromium nitride thin films were deposited on a ZrO2 layer buffered oxide ceramic substrate by the chemical solution deposition method. The effects of annealing temperature on their microstruc...

Columnar nanostructures or ordered nanoarrays of CoFe2O4 (CFO) thin films are desirable in applications. While, the difficulties in achieving large-area columnar CFO thin films with a tunable lateral size and a controllable height/length ratio have limited their applications as synthesizing heterostructures and composites. Herein, CFO thin films with vertically aligned nanorod structures from bottom to up have been achieved on silicon substrates by high magnetic field assisted pulsed laser deposition. Lateral size of the nanorod decreases with increasing the magnetic field. Moreover, both the coercivity and the magnetization at room temperature increase with increasing the magnetic field in deposition. These results will provide a feasible route to deposit large-area and technologically relevant to advance the applications of CFO thin films.

Lead-free thin film capacitors, simultaneously possessing a large energy storage density, ultrahigh efficiency and an extra wide working temperature range, are desirable in applications. In this work, A2Bi4Ti5O18 (A = Ba and Sr) thin films were successfully deposited onto Pt/Ti/SiO2/Si by chemical solution deposition. A large energy storage density (Ure) of 37.1 and 17.2 J cm−3 and a high efficiency (η) of 91.5% and 80.8% were achieved in Ba2Bi4Ti5O18 and Sr2Bi4Ti5O18 thin films, respectively. Moreover, these two thin films show excellent thermal abilities under an extra wide working temperature range from −100 °C to 180 °C. Additionally, high cycling fatigue endurance with a variation of the energy storage density of less than 3.7% and efficiency less than 2.1% after 2 × 108 charge–discharge cycles is obtained for these two thin films. These results indicate that A2Bi4Ti5O18 thin film capacitors have strong potential applications in equipment in harsh working environments.

Epitaxial thin films of perovskite BaSn1–xSbxO3−δ are fabricated by a simple chemical solution deposition method, and the relationship among the processing, the microstructure, and the optoelectronic property is systematically investigated. The process of multiple annealing combined with the postannealing under nitrogen ambient is the optimal procedure to fabricate high quality BaSnO3−δ thin films. Sb doping in Sn sites facilitates the epitaxial growth of the BaSnO3−δ grains. The Hall results show that with increasing Sb doping content the carrier density and the carrier mobility are enhanced and decreased, respectively, resulting in the highest room-temperature electrical conductivity of 260 S/cm in the BaSn0.91Sb0.09O3−δ thin film. It is confirmed that the ionized Sb5+ and oxygen vacancies are the main scattering sources for carrier transport in BaSn1–xSbxO3−δ thin films. The results will provide guidance for synthesis of BaSnO3−δ-based and other donor-doped perovskite transparent conducting large-area ...

We show for the first time that a magnetic field can act as an independent parameter to accelerate the Kirkendall effect in a liquid reaction system. By taking silicon-based nanospheres as a model, it was demonstrated that a magnetic field could efficiently reduce the time of the Kirkendall effect processes at relatively low reaction temperatures. The hollow structure of the product obtained after 5 h under a magnetic field of 1 T is the same as that obtained after 24 h without a magnetic field.

Co-Fe alloy thin films with high magnetization are desirable in numerous applications. Co-Fe thin films prepared by solution methods with refined microstructures have not been achieved up to now. Here, high magnetic field annealing (HMFA) is introduced for the preparation of Co 70 Fe 30 alloy thin films. The effects of HMFA on their microstructures and room temperature magnetic properties are investigated. The thickness of the derived Co 70 Fe 30 thin films is dramatically decreased from a value of 590 nm without HMFA to 320 nm with 7 T magnetic field annealing, and the refinement of microstructures is also observed with HMFA. The derived Co 70 Fe 30 film annealed under 7 T magnetic field exhibits a saturation magnetization of ∼ 2.43 T, close to the theoretical value of 2.45 T. Overall, HMFA provides a feasible way to fabricate larger-area and denser Co-Fe thin films with excellent magnetic properties.

Molybdenum nitrides Mo-N are considered as the hardest superconducting metal nitrides, which are usually prepared under high pressure and high temperature to obtain high superconducting transition temperature T c . Here, polycrystalline δ -MoN thin films with self-assembled c -axis orientation are directly deposited onto Si substrates by chemical solution deposition under ambient NH 3 annealing atmosphere without high pressure processing. The prepared δ -MoN/Si thin films show T c higher than 12 K. The normal state resistivity obeys electron-phonon scattering mechanism and can be well fitted by Bloch-Gruneisen expression. The results will provide an effective route to prepare large-area δ -MoN/Si thin films with high T c as well as a guidance to investigate the fundamental properties of polycrystalline δ -MoN thin films.

CrN thin films are versatile in lots of applications. To develop a facile processing method for large-area CrN thin films with low-cost is unquestionable to improve the technical advances in CrN applications. In this work, CrN thin films are prepared by chemical solution deposition processing for large-area applications. The electrical transport properties are investigated, showing semiconductor-like properties. Magnetoresistance at low temperatures under high magnetic fields is observed in the CrN thin films, showing ultra-low magnetoresistance under 14T of −0.14% and −0.10% at 4.2 and 2 K, respectively.

High magnetic field annealing (MFA) effects on polycrystalline BiFeO 3 (BFO) thin films deposited on ITO buffered glass substrates by the chemical solution deposition (CSD) method have been investigated. Magnetic force induced by magnetic field leads to the increased crystallite size and the decrease in activation energy for boundary motion, especially for the low temperature annealed films. More Fe 3+ ions are induced with increasing magnetic field to lower the free energy of the BFO films, which also leads to a decreased oxygen vacancy, resulting in low leakage current density. The increased remanent polarization and the decreased coercive field initially with the increase in magnetic field are attributed to the reduced domain wall pinning resulted from decreased oxygen vacancies and grain boundaries. Generally, the decreased coercivity and the improved ferroelectric polarization suggest high MFA is an effective way to enhance ferroelectric properties of the CSD-derived BiFeO 3 thin films.

An all-solution approach is successfully used to deposit Bi6Fe2Ti3O18 (BFTO18) thin films onto solution-derived LaNiO3/Si substrates. The effects of annealing temperature on the dielectric, leakage, ferroelectric and magnetic properties are investigated. The mechanisms about the annealing dependence of dielectric, leakage and ferroelectric properties are discussed in detail. Room-temperature weak ferromagnetism is observed for all the derived thin films. The results will provide an effective route to prepare BFTO18 multiferroic thin films with large area by low-cost solution method.

(Bi2Ba3O4−δ)b1/b2CoO2 (BBC) thin films are prepared on LaAlO3 (001) single crystal substrates by chemical solution deposition. The annealing temperature effects on the thin film microstructures as well as transport properties are investigated. The results of X-ray diffraction, energy dispersive spectrometry and transmission electron microscopy confirm the formation of stoichiometric BBC thin films with c-axis orientation. Annealing temperature plays a very important role in determination of resistivity and Seebeck coefficient due to the variations of grain size, carrier concentration and mobility. The resistivity behaviors for the different temperature-annealed thin films obey different electrical transport mechanisms at low, medium and high measured temperature ranges. The optimized BBC thin film is annealed at 600 °C, showing a metal-insulator transition at about 100 K and the resistivity and Seebeck coefficient at 300 K is of 8.7 mΩ cm, 74.4 μV K−1, respectively. The results will provide an effective route to fabricate BBC thin films as well as a guidance for investigation about its transport properties.

CoFe2O4 (CFO) thin films with high coercivity HC are desirable in applications. The difficulty in achieving large-area CFO thin films with high coercivity by sol-gel has hindered the development of CFO thin films. Herein, polycrystalline CFO thin films with the room temperature out-of-plane and in-plane coercivity HC respectively reached ~5.9 and 3.6 kOe has been achieved on the silicon substrate by sol-gel. The room-temperature maximum magnetic energy product (BH)max and remanence ratio Mr/Ms are of 1.66 MG Oe and 0.58 respectively, which are also the largest values amongst the CFO thin films prepared by solution methods. At the same time, annealing temperature and thickness effects on the HC, (BH)max and Mr/Ms of the derived CFO thin films have been investigated. It is observed that grain size and residual tensile strain in the derived films play an important role in the variations of HC and Mr/Ms. These results will provide an effective route for fabricating larger-area high-coercivity CFO thin films with low-cost by sol-gel on silicon wafers.

Bi 6 Fe 2 Ti 3 O 18 thin film on Pt/Ti/SiO 2 /Si substrate with a thickness of 85 nm is successfully prepared by a monoethanolamine-modified sol-gel processing. The prepared thin film is polycrystalline and shows dense morphology. The room temperature remnant polarization is higher than 10 μC cm −2 at 5 V driving voltage both from polarization-voltage hysteresis loop and positive-up negative-down measurements. The polarization after 10 7 switching cycles and a retention time of 10 4 s shows no obvious degradation, suggesting good fatigue-resistant characteristics. Weak ferromagnetism is observed at 5 K with a saturated magnetic moment of 11.7 emu/cm 3 . The results will provide an effective route to optimize Bi 6 Fe 2 Ti 3 O 18 thin films with thickness below 100 nm by low-voltage driving.

Recent progress in transparent conducting components stimulates the extensive exploration of p-type transparent conducting oxide (TCO) materials. Here, we report the synthesis of a class of p-type delafossite Ag-based TCO thin films, AgCrO2 (ACO), using a facile chemical solution route in an open condition. Firstly, the evolution of microstructure, morphology, and optical properties with respect to annealing temperature is reported. The stoichiometric ACO thin films show self-assembled c-axis orientation. The 500 °C-annealed ACO thin film presents a relatively high quality, dense surface and good optical transmittance amongst all the derived thin films. Then, to improve the conductivity, Mg doping effects are investigated. Upon Mg doping, p-type conductivity is obtained for thin films of AgCr1−xMgxO2 (0.04 ≤ x ≤ 0.20). The conductivity initially increases from 3.1 × 10−3 to 67.7 × 10−3 S cm−1 with x increasing from 0.04 to 0.12 and then slightly decreases with further increasing Mg concentration. The Hall results display that the hole concentration gradually increases with increasing Mg dopant concentration, and the carrier mobility first increases with x increasing from 0.04 to 0.12, while decreases with x further increasing from 0.12 to 0.20. A high magnitude of optical transmittance near 60% in the visible region and wide optical bandgaps (3.41–3.66 eV) of the AgCr1−xMgxO2 thin films are observed. The facial fabrication of ACO thin films in an open condition will provide a start for the synthesis of Ag-based delafossite thin films.

The phase-controlled synthesis of metallic and ambient-stable 2D MX2 (M is Mo or W; X is S) with 1T octahedral coordination will endow these materials with superior performance compared with their semiconducting 2H coordination counterparts. We report a clean and facile route to prepare 1T-MoS2 and 1T-WS2 through hydrothermal processing under high magnetic fields. We reveal that the as-synthesized 1T-MoS2 and 1T-WS2 are ambient-stable for more than 1 year. Electrochemical measurements show that 1T-MoS2 performs much better than 2H-MoS2 as the anode for sodium ion batteries. These results can provide a clean and facile method to prepare ambient-stable 1T-phase MX2.

Epitaxial SrRuO 3 (SRO) thin films have been prepared on (100), (110), and (111) LaAlO 3 substrates by chemical solution deposition method, and the microstructures as well as the properties are investigated. The SRO (110) thin films display much more denser, homogeneous and well-connected grains. All the derived SRO thin films show a metallic behavior with low room-temperature resistivity (mΩ·cm). All derived SRO films are ferromagnetic at low temperatures showing different Curie temperature due to the different residual stain, and the SRO (110) film has the largest magnetization and coercivity due to the enhanced morphology. These results will provide a low-cost route to fabricate epitaxial SRO thin films with different orientation.

Multiferroic BiFeO3 (BFO) thin films with a thickness larger than 400 nm are grown on solution-derived LaNiO3 coated Si substrates via chemical solution deposition. The prepared BFO/LaNiO3/Si thin films are strongly (00l)-oriented with a distorted rhombohedral structure of R3c symmetry. The effects of the annealing temperature within the temperature range of 500–650 °C on the microstructures and properties are investigated. With an annealing temperature increasing to 600 °C, the (00l) orientation is enhanced and the grain size is increased, whereas a higher annealing temperature will lead to the deterioration of the orientation and microstructures. The annealing temperature dependent dielectric, leakage and ferroelectric properties are investigated, showing excellent properties for the low temperature annealed BFO thin films. The mechanisms about annealing temperature effects are discussed. The results will provide an effective route to realize the integration of large-area BFO thin films on Si wafers by an all-solution approach with low cost.

Hard/soft interface plays a role in the properties of the composite metal-based magnets, while it is less talked in the composite permanent oxide magnets on the magnetic interaction and properties due to easy interdiffusion. Here, multilayer thin films composed with hard CoFe2O4 phase and soft La0.7Sr0.3MnO3 layers were choose and synthesized without interdiffusion by a chemical solution method. Furthermore, the effects of the annealing temperature and the number of soft layer on the magnetic interaction and properties are investigated. All composite films behavior as one rigidly coupled composite magnet at room temperature, and the magnetic properties increase with increasing annealing temperature. The coercivity and maximum magnetic energy product can respectively reach 8.27 kOe and 2.4 MG Oe at the temperature of 300 K. Exchange coupling was effectively enhanced and even dominate the magnetic interaction with less soft layers for the in-plane direction. Conversely, dipolar interaction predominates, but becomes weak in the composite films with more soft layers and attenuates with increasing annealing temperature for the out-of-plane direction. All of the results suggest that a suitable grain size of the hard phase and an improved interface may be more important for a rigidly coupled composite oxide magnet with good performance.

Vertically aligned nanostructured (VAN) epitaxial La0.5Ca0.5MnO3 (LCMO) single-phase thin films have been achieved on (LaAlO3)0.3(Sr2AlTaO6)0.7 (001) [LSAT (001)] substrates under high magnetic fields applied in pulsed laser deposition processing. Low-field magnetoresistance (LFMR) in the LCMO VAN films can be effectively manipulated through varying the high magnetic field strength. The tunability of VAN on the electrical transport properties is dependent on control of the high magnetic field on the microstructures, including the geometrical arrangement, vertical interfaces, and vertical grain boundaries (GBs). An LFMR value as high as 45% at 150 K and 1 T has been achieved in an LCMO VAN film grown at 10 T, and its LFMR values are larger than 25% at 127–200 K and 1 T. The tunable and enhanced LFMR in the LCMO VAN films over a wide temperature range can be attributed to the increase in vertical interfaces and GB density with the increasing high magnetic field, which are highly related to the spin-polarized tunneling effect. Applying a high magnetic field in film deposition to control the microstructures of VAN single-phase films is a feasible route to achieve tunable and desirable physical properties.

The chemical solution deposition was used to synthesize La0.7Sr0.3MnO3 (LSMO) films. Effects of external magnetic-field (Hext=5 kOe) annealing on microstructure and magnetic properties were investigated. Under the effect of external magnetic field, FE-SEM images indicate that the mean grain size of LSMO film increases. X-ray diffraction results show that all the LSMO films are single-phase rhombohedral structure with a space group of R 3 ¯ C . The coercivity (Hc) of the magnetic-field annealing LSMO film decreases slightly. The values of Curie temperature (TC) and saturation magnetization (Ms) are obviously enhanced, which can be explained by the influence of the magnetic texture and enlarged grain size.

Bismuth ferrite (BiFeO3 ) has recently become interesting as a room-temperature multiferroic material, and a variety of prototype devices have been designed based on its thin films. A low-cost and simple processing technique for large-area and high-quality BiFeO3 thin films that is compatible with current semiconductor technologies is therefore urgently needed. Development of BiFeO3 thin films is summarized with a specific focus on the chemical solution route. By a systematic analysis of the recent progress in chemical-route-derived BiFeO3 thin films, the challenges of these films are highlighted. An all-solution chemical-solution deposition (AS-CSD) for BiFeO3 thin films with different orientation epitaxial on various oxide bottom electrodes is introduced and a comprehensive study of the growth, structure, and ferroelectric properties of these films is provided. A facile low-cost route to prepare large-area high-quality epitaxial BFO thin films with a comprehensive understanding of the film thickness, stoichiometry, crystal orientation, ferroelectric properties, and bottom electrode effects on evolutions of microstructures is provided. This work paves the way for the fabrication of devices based on BiFeO3 thin films.

Polymer-assisted deposition method has been used to fabricate self-assembled epitaxial La0.67Ca0.33MnO3:NiO and La0.67Ca0.33MnO3:Co3O4 films on LaAlO3 substrates. Compared to pulsed-laser deposition method, polymer-assisted deposition provides a simpler and lower-cost approach to self-assembled composite films with enhanced low-field magnetoresistance effect. After the addition of NiO or Co3O4, triangular NiO and tetrahedral Co3O4 nanoparticles remain on the surface of La0.67Ca0.33MnO3 films. This results in a dramatic increase in resistivity of the films from 0.0061 Ω•cm to 0.59 Ω•cm and 1.07 Ω•cm, and a decrease in metal-insulator transition temperature from 270 K to 180 K and 172 K by the addition of 10%-NiO and 10%-Co3O4, respectively. Accordingly, the maximum absolute magnetoresistance value is improved from −44.6% to −59.1% and −52.7% by the addition of 10%-NiO and 10%-Co3O4, respectively. The enhanced low-field magnetoresistance property is ascribed to the introduced insulating phase at the grain boundaries. The magnetism is found to be more suppressed for the La0.67Ca0.33MnO3:Co3O4 composite films than the La0.67Ca0.33MnO3:NiO films, which can be attributed to the antiferromagnetic properties of the Co3O4 phase. The solution-processed composite films show enhanced low-field magnetoresistance effect which are crucial in practical applications. We expect our polymer-assisted deposited films paving the pathway in the field of hole-doped perovskites with their intrinsic colossal magnetoresistance.

In this study, hole-type high-temperature superconductor Bi2Sr2CaCu2Oy (Bi-2212) with strong electronic correlation is proposed as a p-type transparent conducting oxide (TCO) candidate. Phase-pure and c-axis oriented Bi-2212 thin films with different thicknesses were prepared to investigate the optoelectronic properties. High room-temperature conductivity between 1064 and 200 S/cm with visible transmittance over 50% is obtained for the prepared Bi-2212 thin films. The results will provide an arena to search for p-type TCOs in high-temperature superconductors with strong electronic correlation and give a potential application in the field of transparent metallic contacts as well as transparent correlated metal/n-type semiconductor Schottky diodes.

High coercivity CoFe2O4 (CFO) thin films with large-area are very desirable for applications. Here, we report La0.7Sr0.3MnO3 (LSMO) layer decoration effects on coercivity in CFO thin films by solution processing. With LSMO layer decoration, the coercivity increases initially and then decreases with increasing LSMO layer thickness. Strain induced by the mismatched thermal expansion coefficient and magnetostrictive coefficient as well as the interfacial magnetic exchange coupling between CFO and LSMO are investigated. The room temperature out-of-plane and in-plane coercivity reached 7.6 and 4.9 kOe, respectively, are obtained, which are the highest values in solution derived CFO thin films. The improved coercivity is beneficial for applications and provides a facile route to enhance coercivity of CFO thin films through surface modification by soft magnetic layers.

High room temperature coercivity CoFe2O4 (CFO) thin films are desirable in view of many applications, which is seldom achieved over 3 kOe in solution deposited CFO thin films. Herein, grain growth kinetic is investigated in the solution derived CFO thin films with coercivity larger than 4 kOe, showing a relaxation mechanism. The coercivity and magnetization increase initially and then decrease with increasing dwell time. The high coercivity is originated mainly from the critical grain size and the growth strain induced by the small crystallites and poorly developed grains. The results will provide a route to fabricate larger-area CFO thin films with high coercivity on silicon wafers by low-cost solution processing.

LaVO4 thin films have been deposited on Pt / Ti /SiO2 /Si substrates by pulsed laser deposition in order to explore the resistive switching (RS) behavior of the Au/LaVO4/Pt devices. It is found that the as-prepared Au/LaVO4/Pt devices stay in the low resistance state (LRS) and no electroforming process (forming-free) is needed to trigger fresh devices for the subsequent RS. Furthermore, the devices show excellent switching parameters such as a reproducible switching effect, a high resistance ratio of ~104 between the LRS and high resistance state (HRS), good endurance and retention characteristics, and non-overlapping switching voltages. The dominant conduction mechanisms are Ohmic conduction in the LRS and the lower voltage region of the HRS, and Poole–Frenkel emission in the higher voltage region of the HRS. The combination of temperature dependence of resistance, x-ray photoelectron spectroscopy, and model analysis suggests that the forming-free unipolar RS behavior can be explained by the formation and rupture of conical conducting filaments formed out of oxygen vacancies. These results may be important for practical application in nonvolatile resistive switching memory.