LaNiO3 Research Articles

Controlling the Electronic, Structural, and Optical Properties of Novel MgTiO3/LaNiO3 Nanostructured Films for Enhanced Optoelectronic Devices

This study systematically investigated the electronic, structural, and optical properties of MgTiO3 (MTO), LaNiO3 (LNO), and MgTiO3/LaNiO3 (MTO/LNO) nanostructured films grown on Si(100) substrates by the pulsed laser deposition method. The structural characterizations obtained by X-ray diffraction revealed a preferred (003) orientation for the MTO film, while the LNO film was polycrystalline. The diffraction peaks corresponded to a rhombohedral structure, which was confirmed by micro-Raman spectroscopy for both nanostructured films. The MTO/LNO heterostructure was polycrystalline and exhibited the diffraction peaks of both the MTO and the LNO phases. Additionally, the results revealed that the LNO films did not have a significant photoluminescence (PL) emission, while an intense broad infrared luminescence centered at 724 nm appeared for the MTO nanostructured film. Surprisingly, for the MTO/LNO heterostructure, the PL emission profile exhibited a dual-color emission with an intense broad luminescence in...

Magnetic and tunable dielectric properties of DyCrO3 thin films

DyCrO3 (DCO) belongs to the family of rare-earth chromites, some members of which exhibit magnetoelectric multiferroic properties. This work characterizes the dielectric tunability in DCO, which is typically, for conventional ferroelectrics, found to maximize near the ferroelectric to paraelectric transition. Two films of DCO were fabricated via a hybrid solution synthesis route on different substrates: one on single crystalline (001) LaAlO3 (LAO) and the other on (001) LAO coated with a conducting LaNiO3 (LNO) layer. The synthesis method resulted in films with both out-of-plane and in-plane texture in the DCO. The lattice mismatch strain between film and substrate caused a slight increase in the Neel temperature of the DCO film on LAO. Transmission electron microscopy images of the DCO film on the LNO/LAO revealed the epitaxial relationship between these phases. The temperature dependence of the relative permittivity showed diffused transition and a frequency dispersion similar to what is observed in typical relaxor ferroelectrics. Isothermal dielectric constant versus dc electric field measurements showed an electric field tunable relative permittivity (i.e., tunability). This tunability reached a broad plateau near the Neel temperature. Such maxima in dielectric tunability are typically observed near a ferroelectric–paraelectric transition, and its proximity to the magnetic ordering temperature in DCO indicates magnetically driven ferroelectricity in this material.

Magnetoelectric effect in free-standing multiferroic thin film

We prepared two-dimensional close-packed hemispherical CoFe2O4(CFO)/Pb(Zr0.52Ti0.48O3)(PZT)/LaNiO3(LNO)/NiO thin film on Si(100) substrate using a template made of monodispersed polymethyl methacrylate (PMMA) particles. LNO and NiO layers are introduced for the bottom electrode and seed to crystallize, respectively. Since this hemispherical thin film is connected with the substrate only at the “foot” of the hemisphere, this thin film has a hollow structure. Therefore we call this structure as “free-standing” thin film. In this work, we also prepared planar CFO/PZT/LNO/NiO thin film on Si(100) substrate without using the PMMA template for comparison. In this work, we examined the effect of applying a vertical external magnetic field on the ferroelectric property. It was found that applying an external magnetic field decreases remanent polarization (Pr) for both planar and free-standing thin film. The degree of decrease of Pr in the free-standing thin film is about four times larger than that in the planar thin film. This indicates that large multiferroic property (interaction between ferromagnetic and ferroelectric) is realized in the free-standing thin film.

Large orbital polarization in nickelate-cuprate heterostructures by dimensional control of oxygen coordination

Artificial heterostructures composed of dissimilar transition metal oxides provide unprecedented opportunities to create remarkable physical phenomena. Here, we report a means to deliberately control the orbital polarization in LaNiO3 (LNO) through interfacing with SrCuO2 (SCO), which has an infinite-layer structure for CuO2. Dimensional control of SCO results in a planar-type (P–SCO) to chain-type (C–SCO) structure transition depending on the SCO thickness. This transition is exploited to induce either a NiO5 pyramidal or a NiO6 octahedral structure at the SCO/LNO interface. Consequently, a large change in the Ni d orbital occupation up to ~30% is achieved in P–SCO/LNO superlattices, whereas the Ni eg orbital splitting is negligible in C–SCO/LNO superlattices. The engineered oxygen coordination triggers a metal-to-insulator transition in SCO/LNO superlattices. Our results demonstrate that interfacial oxygen coordination engineering provides an effective means to manipulate the orbital configuration and associated physical properties, paving a pathway towards the advancement of oxide electronics.

Relationship Processing–Composition–Structure–Resistivity of LaNiO3 Thin Films Grown by Chemical Vapor Deposition Methods

Precision control of resistivity/conductivity of LaNiO3 (LNO) films is essential for their integration as electrodes in the functional heterostructures. This becomes possible if the relationship between processing parameters–composition–structure–resistivity is determined. LaNiO3 films were deposited by three different chemical vapor deposition methods using different precursor supply systems: direct liquid delivery, pulsed liquid injection, and aerosol generation. The possibilities to ameliorate the efficiency of precursor evaporation and of film growth were studied. The relationship between deposition conditions and composition was determined. Detailed analysis of the epitaxial growth of LNO films on cubic and trigonal substrates and the influence of the rhombohedral distortion on the microstructural quality was done. The resistivity of LaNiO3 films, grown by chemical vapor deposition, was mainly defined by microstructural defects and La/Ni composition. The high epitaxial quality LaNiO3/LaAlO3 films with nearly stoichiometric La/Ni ratio presented low resistivity, which was very close to that of bulk LaNiO3. Their annealing in oxygen atmosphere had little effect on the resistivity, which suggests a minor presence of oxygen vacancies in the as-grown films.

Effect of optical pump on [formula omitted] ultrathin film on [formula omitted] /Si substrate in the terahertz region

PZT (Pb0.52Zr0.48TiO3) ultrathin film (12 nm) was deposited on LNO (LaNiO3) film/silicon substrate by magnetron sputtering. XRD and AFM results show the highly oriented ultrathin PZT film with smooth surface suitable for optical modulation. The figure of merit K was observed increased to highest 0.25 with the 532 nm continuous-wave (CW) pump power increasing to 500mw at 0.5 THz. The variation of the tunability of dielectric permittivity and the loss were attributed to the built-in electric field caused by the optical pump. It was also found that the conduction loss was predominated in the entire loss when the external field increased.

Effects of LNO buffer layers on electrical properties of BFO-PT thin films on stainless steel substrates

Ferroelectric 0.7BiFeO3-0.3PbTiO3 (BFO-PT) thin films were deposited on LaNiO3 (LNO) coated stainless steel (SS) substrates by the sol-gel method. XRD results indicate that both LNO and BFO-PT thin films have the perovskite structure and the film crystallinity is improved with increasing the LNO thickness. The dielectric loss of BFO-PT thin films is reduced significantly with addition of LNO buffer layers, achieving about 4% at the frequency of 1 kHz, much lower than that of >20% for BFO-PT thin films directly deposited on SS substrates. BFO-PT thin films reveal the strong ferroelectricity with remnant polarization (Pr) of about 35 μC/cm2 for LNO of 390 nm. Moreover, addition of LNO buffer layers mitigates the polarization deterioration after the 1.33 × 108 switching cycles resulting in the improved anti-fatigue properties of BFO-PT thin films. Our results indicate that BFO-PT/LNO multilayer thin films on SS substrates maintain excellent dielectric and ferroelectric properties.

Synthesis and characterization of La1-xCexNiO3 with enhanced visible light photocatalytic activities

A series of La1-xCexNiO3 photocatalysts with different content of cerium element have been synthesized by sol-gel method. The as-prepared products were characterized by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photocatalytic activities of these La1-xCexNiO3 composites under visible-light irradiation were evaluated by the degradation of methyl orange (MO). The effect of important operational parameters such as catalyst amount, reaction temperature, irradiation time, and comparison of photocatalytic activity with different dyes including methyl orange, alizarin red, alizarin yellow, xylenol orange were also studied. The results revealed that the La0.8Ce0.2NiO3 (LCNO) composites exhibited much higher photocatalytic activities than pure LaNiO3 (LNO).

Controlled spalling and flexible integration of PZT film based on LaNiO3 buffer layer

As a functional ferroelectric material, PbZr0.53Ti0.47O3 (PZT) film is widely used in many electronic devices. However, with the rapid development of intelligent terminal, traditional PZT device cannot meet the demand for flexible wearable devices. In this work, a high-quality flexible PZT film is fabricated by the controlled spalling technology (CST) for the first time, which is novel, simple and cost-efficient. LaNiO3 (LNO) film by sol-gel process is used as the buffer layer for the PZT film growth due to good lattice match and low cost. The PZT film on silicon substrate is successfully transferred onto a flexible one by electroplating Ni stressor layer. LNO buffer layer thickness has an important influence on the spalled silicon depth and Ni stressor layer thickness during the spalling process. The exfoliated PZT film based on sandwich capacitor structure Au/PZT/Au with an area of 1 cm2 exhibits good ferroelectric properties under different mechanical deformation. Moreover, the ferroelectric response of flexible PZT film does not show obvious deterioration after repeated operation cycles. Therefore, the flexible PZT thin film has a good application prospect on wearable ferroelectric microelectronics.

Giant dielectric phenomenon of Ba0.5Sr0.5TiO3/CaCu3Ti4O12 multilayers due to interfacial polarization for capacitor applications

Ba0.5Sr0.5TiO3/CaCu3Ti4O12 (BST/CCTO) multilayers with different stack sequences were deposited on LaNiO3(LNO)/SiO2/Si substrates by a sol-gel process. The dielectric properties of BST/CCTO multilayers are significantly affected by the deposition sequence, the layer thickness and the impurities, effects that are interpreted using the Maxwell-Wagner interfacial polarization model. Impurities are generated by elemental interdiffusion at the interfaces of BST/CCTO, and less at the interfaces of BST/LNO and CCTO/LNO. The dielectric permittivity of the CCTO/BST/LNO/SiO2/Si sample reaches 352,200 at 10 kHz, and stabilizes above 20,000 in the range of 100 kHz to 1 MHz. This work demonstrates an effective approach to enhance dielectric properties for film capacitor applications by constructing multilayers with specific deposition sequences and layer thicknesses.

Flexible vibrational energy harvesting devices using strain-engineered perovskite piezoelectric thin films

The material properties of Pb(Zr,Ti)O3 (PZT) thin film with a LaNiO3 (LNO) buffer layer on an ultra-thin Ni-Cr-based austenitic steel metal foil substrate are systematically investigated for flexible piezoelectric vibrational energy harvesting device applications. The use of the flexible austenitic metal foil substrate with a high thermal expansion coefficient results in the large compressive stress in the deposited PZT thin film, and subsequently produces much enhanced ferroelectric polarization of the film. The measured polarization value of the PZT film on the flexible metal foil substrate is over 50 µC/cm2, showing a great improvement in comparison with the film on the conventional Pt/Ti/SiO2/Si substrate. Simultaneously, the LNO buffer layer prevents any undesirable reactions, provides uniform nucleation sites and promotes easy crystallization of the PZT thin film, achieving the highly dense and uniform microstructure of the film with a smooth surface. Using the strain-engineered PZT thin film, a small-scale and flexible vibrational energy harvester is fabricated using a simple punching process without any complex microelectromechanical system (MEMS) or etching processes. The maximum power and the corresponding peak voltage of the device are 5.6 µW and 690 mV, respectively, which are much higher values than those of MEMS-based vibrational energy harvester. The improved device performance of our flexible small-scale vibrational energy harvester is due to the enhanced PZT film properties by the stress engineering, the increased flexure and deflection of the flexible structure, and the easy vibrational sensitivity at low acceleration of 0.5g, compared to the MEMS-based device integrated with conventional Si-based substrates. The results prove that our strain-tuned PZT thin film-based flexible vibrational piezoelectric energy harvester is a promising candidate for autonomous power systems and future small-scale mobile platforms.

Effect of electrode interfaces on peak-drift switching current of PZT thin films

In this study, we investigated the impact of electrodes on the structural, crystal orientation, and electrical characteristics of lead zirconate titanate [Pb(Zr0.52Ti0.48)O3, PZT] thin films, that were deposited on Pt, Au, and LaNiO3 (LNO) electrodes through sol-gel processes. The peak voltage, that is, the voltage corresponding to the maximum switching current point, was developed to depict the novel peak-drift electric characteristics in ferroelectric thin films. It increases in the positive ferroelectric peak voltage, and decreases in the negative peak voltage with an increase in the driving voltage amplitude. Based on space-charge-limited bulk conduction, we evaluated the peak-drift phenomenon, Schottky contact and their influences on the switching current. When polarization orientation is reversed, the Schottky contact disappears at one side of the PZT/electrode, and forms at the other side synchronously. Our results indicate that the formation of a Schottky contact affects the shape of the switching curves, and its disappearance influences the magnitude of the current characteristics.

Tuning spin one channel to exotic orbital two-channel Kondo effect in ferrimagnetic composites of LaNiO3 and CoFe2O4

We report the tuning from spin one channel to orbital two-channel Kondo (2CK) effect by varying CoFe2O4 (CFO) content in the composites with LaNiO3 (LNO) along with the presence of ferrimagnetism. Although there is no signature of resistivity upturn in the case of pure LNO, all the composites exhibit a distinct upturn in the temperature range of 30–80 K. For composites with lower percentage of CFO (10%), the electron spin plays the key role in the emergence of resistivity upturn which is affected by external magnetic field. On the other hand, when the CFO content is increased (⩾15%), the upturn shows strong robustness against high magnetic field (⩽14 T) and a crossover in temperature variation from to T1/2 at the Kondo temperature, indicating the appearance of orbital 2CK effect. The orbital 2CK effect originates due to the scattering of conduction electrons from the structural two-level systems which is created at the interfaces between the two phases (LNO and CFO) of different crystal structures as well as inside the crystal planes. The specific heat data at low temperature (⩽40 K), deviates from the usual linear temperature variation of the electronic contribution. With higher CFO content it shows more deviation which also indicates the increasing amount of two-level system. A negative magnetoresistance (MR) is observed at low temperature (<30 K) for composites containing both lower (10%) and higher percentage (15%) of CFO. We have analyzed the negative MR using Khosla and Fisher semi-empirical model based on spin dependent scattering of conduction electrons from localized spins.

Reduced leakage current, enhanced energy storage and dielectric properties in (Ce,Mn)-codoped Ba0.6Sr0.4TiO3 thin film

Ba0.6Sr0.4TiO3, Ce-doped Ba0.6Sr0.4TiO3, Mn-doped Ba0.6Sr0.4TiO3, (Ce,Mn) co-doped Ba0.6Sr0.4TiO3 (abbreviated as BST, BSTCe, BSTMn, BSTCeMn) thin films were deposited on LaNiO3(LNO)/Si substrates. The effects of ion doping on the microstructure and electrical properties of BST-based thin film have been researched and discussed. The X-ray diffraction pattern shows that each sample has pure perovskite phase structure with high (l00) peaks. The microstructure of each film is quite dense with uniform size. Compared with pure BST, improved insulating properties can be found in ion-doped BST thin films. For all the films, Ohmic conduction, space charge limited conduction and interface-limited Fowler-Nordheim tunneling should be the main conduction mechanisms within different electric field regions. For the case of BSTCeMn thin film, it possesses enhanced energy storage performance with a recoverable energy storage density (18.01 J/cm3) and a energy storage efficiency (75.1%) under 2000 kV/cm. This can be closely related to the small remanent polarization value (Pr= 1.89 μC/cm2), large maximum polarization value (Pmax= 28.08 μC/cm2) as well as big maximum electric field (2000 kV/cm). Also, it exhibits a large dielectric constant of 405 and a small dissipation factor of 0.075 at 500 kHz.

Interfacial magnetism in La0.7Sr0.3MnO3/LaNiO3 ultrathin superlattices

We report a detailed study of the structural and magnetic properties of pulse laser deposition grown superlattices (SLs) comprising of metallic ferromagnet La0.7Sr0.3MnO3 (LSMO) and paramagnet LaNiO3 (LNO) with the stacking order [(LSMO)d/(LNO)t]15 (d = 3.3 nm, t = 1.5 nm, 3 nm, 5 nm) on (1 1 1) and (0 0 1) − oriented SrTiO3 (STO) single crystal substrates. The x-ray reflectivity data and diffraction of SLs reveal the well-defined smooth and periodic nature of the SLs. The reciprocal space mapping provides the evidence of coherently strained epitaxial layers of the perovskite structures with long-range periodicity. The [(LSMO)3.3/(LNO)3]15 SL on STO (1 1 1) exhibits a positive exchange-bias effect, which indicates the induced-magnetization with interface driven antiferromagnetic coupling in (1 1 1)-stacking. The robust magnetic ordering was observed for a SL grown on (1 1 1)-oriented STO as compared to the (0 0 1) stacked SLs. Beyond 1.5 nm thickness of LaNiO3, all of the above anomalous magnetic characteristics of SLs seizes away. The interface induced magnetism in the LNO layers was discussed using the temperature and magnetic field dependence of magnetization measurements.

High-Temperature Thermoelectricity in LaNiO3-La2CuO4 Heterostructures.

Transition metal oxides exhibit a high potential for application in the field of electronic devices, energy storage, and energy conversion. The ability of building these types of materials by atomic layer-by-layer techniques provides a possibility to design novel systems with favored functionalities. In this study, by means of the atomic layer-by-layer oxide molecular beam epitaxy technique, we designed oxide heterostructures consisting of tetragonal K2NiF4-type insulating La2CuO4 (LCO) and perovskite-type conductive metallic LaNiO3 (LNO) layers with different thicknesses to assess the heterostructure-thermoelectric property-relationship at high temperatures. We observed that the transport properties depend on the constituent layer thickness, interface intermixing, and oxygen-exchange dynamics in the LCO layers, which occurs at high temperatures. As the thickness of the individual layers was reduced, the electrical conductivity decreased and the sign of the Seebeck coefficient changed, revealing the contribution of the individual layers where possible interfacial contributions cannot be ruled out. High-resolution scanning transmission electron microscopy investigations showed that a substitutional solid solution of La2(CuNi)O4 was formed when the thickness of the constituent layers was decreased.

Conductive-perovskite LaNiO3 thin films prepared by using solution process for electrode application

Lanthanum nickel oxide LaNiO3 (LNO) is extensively known as one of typical perovskite-structured materials with metallic conductivity, which is suitable for the electrode application in electronic devices such as transistors or solar cells. Since LNO is a low-cost material and a simple fabrication process, it has been attracted much attention for commercialization. In this paper, we have focused on optimizing the fabrication process of LNO thin films on SiO2/Si substrate and Al foil by using a solution process. The crystal structure and surface morphology were characterized by using X-ray diffraction and field-emission scanning electron microscopy (FE-SEM), respectively. It was found that the LNO thin films annealed in range of 550-700oC for 30 min exhibited a well-formed crystallization and a dense microstructure. According to the SEM cross-sectional observation, the thickness of LNO thin films was estimated about 80 nm. Also, from the four-probe measurement method, the electrical resistivity of LNO thin film annealed at 600oC had a minimum value of 0.42 × 10-2 Ωcm, which was possibly comparable to conventional conductive oxides. As a result, the capacitor using Pb1.2(Zr0.4Ti0.6)O3 ferroelectric layer annealed at 600oC and LNO bottom electrode provided an interesting ferroelectricity, which included a remnant polarization of 21 µC/cm2 and a saturated polarization of 35 µC/cm2. Moreover, the leakage current density was lower than 2 × 10-5 A/cm2.

Tailoring Ferroelectric Properties of 0.37BiScO3–0.63PbTiO3Thin Films Using a Multifunctional LaNiO3Interlayer

Functional oxide thin films integrated into CMOS technology often exhibit degraded properties with respect to bulk materials because of complex interfacial phenomena. In this contribution, we demonstrate that a sol-gel LaNiO3 (LNO) interlayer deposited onto the surface of a Pt/TiO2/SiO2/Si substrate prior to growth of sol-gel BiScO3-PbTiO3 (BSPT) films acts: i) to seed nucleation of perovskite structured; ii) to template growth to give controlled orientation and enhanced crystallinity and iii) as a sink for oxygen vacancies (VO). The LNO interlayer therefore not only improves the ferroelectric, piezoelectric and dielectric properties but also reduces leakage current and prevents degradation of the remanent polarization during fatigue tests. We propose that the use of a LNO interfacial layer may offer a generic solution to interfacial degradation in functional oxide films.

High energy-storage performance of BNT-BT-NN ferroelectric thin films prepared by RF magnetron sputtering

Dielectric materials with high energy-storage density and efficiency have great potential applications in modern electric and electronic devices. In this work, a series of 0.9(0.94Bi0.5Na0.5TiO3-0.06BaTiO3)-0.1NaNbO3 (BNT-BT-NN) ferroelectric thin films were deposited on LaNiO3 (LNO) bottom electrodes by radio-frequency (RF) magnetron sputtering technique. The effects of different annealing temperature on microstructure, dielectric property and energy-storage performance of these thin films were studied in detail. Post-deposition annealing of BNT-BT-NN thin films at an appropriate temperature of 650 °C was found to greatly improve the film structure and enhance the electrical characteristics, such as dense structure, smooth surface, low leakage current density, high breakdown strength (BDS) and large difference between maximum and remanent polarization. As a result, a huge energy-storage density of 32 J/cm3 and a large energy-storage efficiency of 90% were achieved under 3170 kV/cm in the thin film which was annealed at 650 °C. Moreover, the thin film exhibited a stable energy-storage performance under different temperature and frequency. Therefore, BNT-BT-NN thin film with proper annealing temperature is a promising candidate for high energy-storage capacitors.

Role of the Carbon Support on the Oxygen Reduction and Evolution Activities in LaNiO3 Composite Electrodes in Alkaline Solution

Metal–air batteries and fuel cells show a great deal of promise in advancing low-cost, high-energy-density charge storage solutions for sustainable energy applications. To improve the activities and stabilities of electrocatalysts for the critical oxygen reduction and evolution reactions (ORR and OER, respectively), a greater understanding is needed of the catalyst/carbon interactions and carbon stability. Herein, we report how LaNiO3 (LNO) supported on nitrogen-doped carbon nanotubes (N-CNT) made from a high-yield synthesis lowers the overpotential for both the OER and ORR markedly to enable a low bifunctional window of 0.81 V at only a 51 μg cm–2 mass loading. Furthermore, the addition of LNO to the N-CNTs improves the galvanostatic stability for the OER by almost 2 orders of magnitude. The nanoscale geometries of the perovskites and the CNTs enhance the number of metal–support and charge transfer interactions and thus the activity. We use rotating ring disk electrodes (RRDEs) combined with Tafel slope ...