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Correlated transparent conducting oxides (TCOs) have gained great attention, because of their unique combination of transparency and metallic character. SrVO3(SVO) was identified as a high-performance TCO in the visible range. Few studies have investigated band structure engineering through chemical doping to enhance the optical properties of SVO. Here, we use two different strategies by exploiting the band-filling and width of the bands derived from Vanadium to tune the screened plasma frequency ωp*and the interband transition Ep–denergy, corresponding to the optical transparency window edges. For control of the band-filling strategy, it is found that Titanium doped SVO has a wide transparency window, but such a composition does not maintain the high electrical conductivity required for TCO applications. Concerning the bandwidth strategy, the doping of SrVO3by Calcium shows that ωp*remains located in the IR range (1.12 eV), while Ep–dis blue-shifted into the UV region (3.43 eV) due to reinforced electronic correlations. By an appropriate choice of dopant, we successfully increased the size of the transparency window by around 11% from 1.94 eV (SVO) to 2.30 eV (Calcium-doped SVO), while retaining high conductivity of around 2.30 × 104(S·cm–1) and high charge carrier density of 2.93 × 1022cm–3.

We explored the time dependence of the nanoscale domain relaxation mechanism in epitaxial K0.5Na0.5NbO3(KNN) thin films grown on La0.67Sr0.33MnO3/SrTiO3(001) substrates over the thickness range 20–80 nm using scanning probe microscopy. Kelvin probe force microscopy (KFM) and piezoresponse force microscopy were performed on pulsed-laser-deposition-deposited KNN thin films for studying the time evolution of trapped charges and polarized domains, respectively. The KFM data show that the magnitude and retention time of the surface potential are the maxima for 80 nm-thick film and reduce with the reduction in the film thickness. The charging and discharging of the samples reveal the easier and stronger electron trapping compared to hole trapping. This result further indicates the asymmetry between retention of the pulse-voltage-induced upward and downward domains. Furthermore, the time evolution of these ferroelectric nanodomains are found to obey stretched exponential behavior. The relaxation time (T) has been found to increase with increase in thickness; however, the corresponding stretched exponent (β) is reduced. Moreover, the written domain can retain for more than 2300 min in KNN thin films. An in-depth understanding of domain relaxation dynamics in Pb-free KNN thin films can bridge a path for future high-density memory applications.

We have probed the structural and magnetic properties of PrVO3(PVO) thin films grown on the (001)-, (110)-, and (111)-oriented SrTiO3(STO) substrates. By changing the substrate orientation, the film out-of-plane orientation can be tuned to [110], [100]/[010], and [011]/[311], with different in-plane crystallographic variants. Accommodation of these variants on the different substrates implies different strain states, which have direct influence on the magnetic properties of PVO films. The magnetic moment of PVO films radically enhances from 0.4 μB/f.u. for STO(001) to 2.3 μB/f.u. for STO(111). While films on the (001)-oriented STO substrate display out-of-plane anisotropy, an in-plane anisotropy is observed for films grown on the (110)- and (111)-oriented STO substrates. In addition, a strong uniaxial magnetic anisotropy is also extracted for a partially relaxed film on the (110)-oriented STO substrate. Such findings can help oxide community for the better understanding of magnetic anisotropy in vanadate thin films, a subject that still suffer from significant lack of scientific investigations.

New paradigms are required in microelectronics when the transistor is in its downscaling limit and integration of materials presenting functional properties not available in classical silicon is one of the promising alternatives. Here, we demonstrate the possibility to grow La0.67Sr0.33MnO3(LSMO) functional materials on amorphous substrates with properties close to films grown on single-crystalline substrates using a two-dimensional seed layer. X-ray diffraction and electron backscatter diffraction mapping demonstrate that the Ca2Nb3O10–nanosheet (NS) layer induces epitaxial stabilization of LSMO films with a strong out-of-plane (001) texture, whereas the growth of LSMO films on uncoated glass substrates exhibits a nontextured polycrystalline phase. The magnetic properties of LSMO films deposited on NS are similar to those of the LSMO grown on SrTiO3single-crystal substrates in the same conditions (which is used as a reference in this work). Moreover, transport measurements take advantages of the texture and polycrystalline properties to induce low-field magnetoresistance at low temperature and also a high value of 40% magnetoresistance from 10 to 300 K, making it interesting for sensor applications. Therefore, the NS seed layer offers new perspectives for the integration of functional materials grown at moderate temperatures on any substrate, which will be the key for the development of oxitronics.

A strong perpendicular magnetocrystalline anisotropy (PMA) in antiferromagnetically coupled SrRuO3(17 uc (unit cell))/PrMnO3(nuc) superlattices effectively reconstructs the interfacial spin ordering. The occurrence of significant anisotropic interfacial antiferromagnetic coupling between the Ru and Mn ions is systematically tuned by varying the PrMnO3layer thickness in ultrathin scale from 3 to 12 uc, which is associated with a rise in PMA energy from 0.28 × 106to 1.60 × 106erg/cm3. The analysis using the Stoner–Wohlfarth model and density functional theory confirm that the exchange anisotropy is the major contribution to the PMA. The superlattices with PrMnO3layer thickness ≥7 uc exhibit the tunneling-like transport of Ru 4d electrons, which is rather expected in the stronger antiferromagnetically coupled superlattices with thinner PrMnO3layer. Tunneling-like transport at thicker spacer layer in the SrRuO3–PrMnO3superlattice system is an unique feature of two ferromagnet-based superlattices. Our investigations show that the technologically important interfacial magnetic coupling, PMA, and tunneling magnetoresistance could be achieved in a periodically stacked bilayer and can be precisely manipulated by the size effect in ultrathin scale.

The functional properties of oxide heterostructures depend on the interfaces accommodating ions, their spins, and structural mismatches. Here, by stabilizing tetragonal symmetry, we achieve the in-plane antiferromagnetic (AFM) ordering and dual-exchange bias in the superlattices consisting of two ferromagnets SrRuO3(SRO) and PrMnO3(PMO). The tetragonal symmetry of this superlattice system achieved after the octahedral rotations yield an elongation of the c-axis parameter with Ru–O–Mn bond angle close to 180°, induces an interfacial antiferromagnetic ordering, which is suppressed as the ferromagnetic (FM) ordering in the PMO layer increases. The 0.1 T in-plane cooling field (Hcool) leads to the shift (ca. −0.04 T) of minor hysteresis loop along the negative field axis due to the presence of −0.87 erg/cm2AFM interfacial exchange coupling energy density (ERu,Mn) at 20 K. The exchange bias field (HEB) switches from negative to positive value with the increase in Hcool. For 5 T Hcool, the HEBis positive, but the ERu,Mnis −1.25 erg/cm2for n≤ 8 (n= number of unit cells of PMO) and 1.52 erg/cm2for n≥ 8. The HEBand its switching from negative to positive with the increase in Hcoolare explained by the interplay of strong antiferromagnetic coupling energy and Zeeman energy at the interfaces. The results demonstrate that the SRO–PMO superlattice could be a model system for the investigation of the interfacial exchange coupling in functional oxides.

Abstract

SrVO3(SVO) is a prospective candidate to replace the conventional indium tin oxide (ITO) among the new generation of transparent conducting oxide (TCO) materials. In this study, the structural, electrical, and optical properties of SVO thin films, both epitaxial and polycrystalline, are determined during and after heat treatments in the 150–250 °C range and under ambient environment in order to explore the chemical stability of this material. The use of these relatively low temperatures speeds up the natural aging of the films and allows following the evolution of their related properties. The combination of techniques rather sensitive to the film surface and of techniques sampling the film volume will emphasize the presence of a surface oxidation evolving in time at low annealing temperatures, whereas the perovskite phase is destroyed throughout the film for treatments above 200 °C. The present study is designed to understand the thermal degradation and long-term stability issues of vanadate-based TCOs and to identify technologically viable solutions for the application of this group as new TCOs.

Capacitors with a dielectric material consisting of amorphous laminates of Al2O3and TiO2with subnanometer individual layer thicknesses can show strongly enhanced capacitance densities compared to the bulk or laminates with nanometer layer thickness. In this study, the structural and dielectric properties of such subnanometer laminates grown on silicon by state-of-the-art atomic layer deposition are investigated with varying electrode materials. The laminates show a dielectric constant reaching 95 combined with a dielectric loss (tan δ) of about 0.2. The differences of the observed dielectric properties in capacitors with varying electrodes indicate that chemical effects at the interface with the TiN electrode play a major role, while the influence of the local roughness of the individual layers is rather limited.

L’élaboration des matériaux multiferroïques sous forme de couches minces permet l’obtention de phases chimiques métastables ou sous contrainte, et la conception de nouveaux matériaux artificiels, composites ou multicouches, ouvrant une voie très prometteuse pour les applications dans l’électronique intégrée.

In this paper, we discuss the utility of thin film deposition as a synthetic approach to the realization of new oxide materials. Thin film deposition has been shown previously to be well suited to stabilizing both highly metastable phases and superlattices having unique atomic order which are not attainable via classical preparatory routes. That this approach is only in the early stages of realizing its full potential as a synthetic method is demonstrated using classical pulsed laser deposition to grow new, artificially layered materials. Superlattices of metastable copper and manganese oxides having perovskite-like sub-cells were grown; they have the nominal formulae (La0.8Ba0.2CuO2.6±x)m(SrCuO2+δ)n and (LaMnO3)m(A′MnO3)n (A′=Sr and Y). Superlattice reflections are observed in the X-ray diffraction spectra, indicative of a two-dimensional cationic order not observed in bulk materials of similar stoichiometries. Moreover, the chemistry of the dimensionally confined layers in the superlattices differs from that of similar ‘bulk-like’ materials. Anomalous CMR effects are presented for the (LaMnO3)m(SrMnO3)n superlattices, demonstrating that new and unique physical properties are attainable via this particular synthetic approach. We also discuss the structure and growth mode of single films of LaMnO3 with respect to superlattice formation.

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