This study explores precise control over ferroelectric (Q) and antiferroelectric (P) phase transitions in NaNbO3 (NNO) thin films, essential for sustainable electronic applications. Epitaxial NNO layers (10-290 nm) were grown via Pulsed Laser Deposition (PLD) onto SrTiO3 (001) and NdGaO3 (110)/(101). X-ray diffraction and reciprocal-space mapping show films deposited at 600 degrees C nucleate as a fully strained Q phase; beyond a thickness of about 45 nm on NdGaO3, they relax into the P phase. Elevated deposition temperature (750 degrees C) facilitates early partial relaxation of the Q-phase and promotes nucleation and growth of the P-phase, evident from distinctive morphologies observed by Atomic Force Microscopy (AFM). Conductive AFM further links structural phases to their distinct electrical signatures, showcasing ferroelectric hysteresis in Q-phase regions and more complex loops in P/Q mixed-phase domains. Notably, on NdGaO3 (101), we demonstrate distinct single-phase growth; by selecting deposition temperature, we obtain exclusively the Q or P phase, without mixed states. These results provide insights into controlling structural transitions in NNO thin films, guiding their future development for sustainable electronics, energy storage, piezoelectric microdevices, and multifunctional systems.

Tungsten oxide WO₃₋ₓ thin films were synthesized using the spray pyrolysis technique on glass substrates heated to 350 °C, employing tungsten hexachloride (WCl₆) as the precursor. The films were annealed at the same temperature for 5 hours. Their structural properties were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analysis revealed that the as-deposited films crystallized in a monoclinic W₁₈O₄₉ (WO₂.₇₂) phase, while annealing induced a phase transformation to tetragonal W₅O₁₄ (WO₂.₈). Optical measurements indicated a wide direct optical band gap of 3.5 eV for WO₂.₇₂, which increased to 3.8 eV for WO₂.₈ after annealing, accompanied by a reduction in Urbach energy. Electrical properties were analyzed using impedance spectroscopy in the frequency range of 100 kHz–13 MHz at temperatures between 200 and 275 °C. Nyquist plot fitting revealed contributions from both grain interiors and grain boundaries to the relaxation process, with a non-Debye poly-dispersive behavior. Additionally, the activation energy decreased post-annealing. The as-deposited films exhibited excellent photocatalytic performance in the degradation of methylene blue under solar irradiation. This enhanced activity was attributed to the presence of oxygen vacancies and a comparatively lower band gap relative to the annealed films. This study not only highlights the phase transformation of WO₃₋ₓ to WO₃ induced by thermal annealing but also demonstrates the potential of WO₂.₇₂ thin films in photocatalytic dye degradation applications.

The morphotropic phase boundary (MPB) composition in lead free (1-x) Bi0.5Na0.5TiO3-x BaTiO3 (BNTBT) solid solution has attracted extensive research due to its significant potential for piezoelectric and high-power energy storage applications. Here, epitaxial (001) and (111) BNTBT films with composition around the MPB are investigated. A complex domain pattern is evidenced for both film orientation, due to the coexistence of a weak polar phase and a strong polar ferroelectric phase. An electric field induced phase switching is shown in both (001) and (111) oriented film, as well as a weakening of the polar state in the (111) BNTBT film. The enhanced ergodic relaxor state in the (111) BNTBT film gives rise to a reduced piezoelectric response and improved energy storage performances. The epitaxial symmetry engineering is shown to provide a complementary approach to the composition strategy to improve the functional properties in BNTBT films.

In this paper, the effect of the post-annealing temperature on the structural and electrical properties at macro and nanoscale of Sodium Bismuth Titanate - Bi0.5Na0.5TiO3 (BNT) films is reported. Stoichiometric BNT thin films were deposited by ex-situ radio frequency (rf) sputtering at substrate temperature of 200 degrees C. The as-deposited films were amorphous and post-annealing treatment was necessary to crystallize the film in the perovskite phase. 400-nm-thick stoichiometric BNT films were annealed at various temperatures from 400 degrees C up to 700 degrees C. The BNT film annealed at 400 degrees C remains amorphous. Film starts to crystallize at 450 degrees C and then the crystallization increases with the post-annealing temperature to reach an optimal at 650 degrees C without any secondary phase. Dielectric, ferroelectric and piezoelectric properties were also improved with the increasing of the postannealing temperature. The piezoelectric coefficient d33eff, measured at macroscale, reaches a maximum value of 57 pm/V for 400 nm-thick film post-annealed at 650 degrees C. On nanoscale, measurements performed by piezoresponse force microscopy are in perfect concordance with the performances obtained at macroscale. The efficient polarization reversal for domains and their retention when locally manipulated are observed, combined to a strong piezo-activity.

Integrating tunneling magnetoresistance (TMR) effect in memristors is a long-term aspiration because it allows to realize multifunctional devices, such as multi-state memory and tunable plasticity for synaptic function. However, the reported TMR in different multiferroic tunnel junctions is limited to 100%. This work demonstrates a giant TMR of -266% in La0.6Sr0.4MnO3(LSMO)/poly(vinylidene fluoride)(PVDF)/Co memristor with thin organic barrier. Different from the ferroelectricity-based memristors, this work discovers that the voltage-driven florine (F) motion in the junction generates a huge reversible resistivity change up to 106% with nanosecond (ns) timescale. Removing F from PVDF layer suppresses the dipole field in the tunneling barrier, thereby significantly enhances the TMR. Furthermore, the TMR can be tuned by different polarizing voltage due to the strong modification of spin-polarization at the LSMO/PVDF interface upon F doping. Combining of high TMR in the organic memristor paves the way to develop high-performance multifunctional devices for storage and neuromorphic applications.

Ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-co-TrFE)] thin films have been deposited by spin-coating onto the Bi0.5Na0.5TiO3(BNT)/LNO/SiO2/Si heterostructure. The copolymer microstructure investigated by using grazing-incidence wide-angle X-ray diffraction (GIWAXD) and deduced from the (200)/(110) reflections demonstrates that the b-axis in the P(VDF-co-TrFE) orthorhombic unit cell is either in the plane or out of the plane, depending on the face-on or on the two types of edge-on (called I and II) lamellar structures locally identified by atomic force microscopy (AFM). For edge-on I lamellae regions, the electroactivity (dzzeff ∼ -50.3 pm/V) is found to be twice as high as that measured for both edge-on II or face-on crystalline domains, as probed by piezoresponse force microscopy (PFM). This result is directly correlated to the direction of the ferroelectric polarization vector in the P(VDF-co-TrFE) orthorhombic cell: larger nanoscale piezoactivity is related to the b-axis which lies along the normal to the substrate plane in the case of the edge-on I domains. Here, the ability to thoroughly gain access to the as-grown polar axis direction within the edge-on crystal lamellae of the ferroelectric organic layers is evidenced by combining the nanometric resolution of the PFM technique with a statistical approach based on its spectroscopic tool. By the gathering of information at the nanoscale, two orientations for the polar b-axis are identified in edge-on lamellar structures. These findings contribute to a better understanding of the structure-property relationships in P(VDF-co-TrFE) films, which is a key issue for the design of future advanced organic electronic devices.

Un-doped, Zn-doped, and Al–Zn co-doped CdO thin films were deposited onto glass substrates at 350 °C by spray pyrolysis. X-ray diffraction (XRD) analysis was conducted to investigate the structural properties of the films. The XRD patterns confirmed that all the films crystallize in a cubic structure and that the addition of Zn and Al did not alter the CdO crystal structure. Energy-dispersive X-ray spectroscopy analysis further confirmed the successful incorporation of Zn and Al into the CdO films. Theoretical calculations based on first-principles were performed, and crystallographic information files (CIF) were obtained for optimized theoretical supercells in space group Pm3-m. The CIF files were used as input for experimental XRD spectra Rietveld refinement, to determine the Wyckoff positions of the dopants and their occupation rates. The optical properties of the films were characterized using transmittance measurements in the wavelength range of 300–1700 nm. The optical data indicated an increase in the average transmittance from 60 to 70% within the wavelength range of 600–1700 nm upon Al–Zn co-doping. The estimated direct optical band gap of the un-doped, doped, and co-doped CdO thin films is varied between 2.41 and 2.50 eV. All the samples exhibited n -type conductivity with low electrical resistivity of about 1.32 × 10 –4 Ω⋅cm. Co-doped CdO thin films with 1% Al and 3% Zn exhibited higher carrier concentration (4.39 × 10 +20 cm −3 ) than the other samples.

Presently, metallic nanowires (NWs) are the most promising materials to fabricate flexible transparent electrodes as an alternative to indium tin oxide. Here, the high performance of transparent conductive electrodes (TCEs) based on silver nanowires (AgNWs) percolation networks is reported. With optimized experimental conditions for the deposition, the AgNWs result in low sheet resistance of 10 Ω sq −1 combined with a high optical transmittance of 92.6% at λ = 550 nm. This leads to a valuable figure of merit as compared to other TCEs. In this study, the nanoscale electrical properties of the AgNWs are measured via conductive atomic force microscopy to characterize the percolation network. The electrical resistivity value calculated for a single AgNW is found to be about 12.35 µΩ cm, while a nanoscale conductivity map over an AgNW network bridging two electrodes has revealed high levels of current within the network over a distance of more than 1000 µm. The favorable determined conductivity results along with the high optical properties of the AgNWs network strongly suggest that thin‐film electrodes based on AgNWs will be a potential approach for future flexible electronic devices.

An orthorhombic alpha-Pr2WO6 (PrWO) polymorph with a = 16.57(5) angstrom, b = 5.52(5) angstrom, and c = 8.73(1) angstrom, isostructural to alpha-La2WO6 and alpha-Nd2WO6 , has been stabilized in the form of thin film by pulsed laser deposition on (001)-oriented SrTiO3 substrates. Combining X-ray diffraction pole-figure measurements and transmission electron microscopy (TEM) analysis, the c-axis films gave evidence of the orientations [100]PrWO || [110]STO and [010]PrWO || [110]STO in the plane. Advanced phi-scans and reciprocal space mapping characterizations confirm the existence of the orthorhombic (Pm21n) structure in the film in place to the tetragonal one as also suggested. X-ray thermodiffraction measure-ments highlight the stability of this polymorph in thin film up to 900 degrees C at least. Optical measurements performed by spectroscopic ellipsometry reveal that the band gap in such 36 nm thick films (as confirmed by both X-ray reflectivity and TEM measurements) is 2.5 eV. Besides, the local piezoelectric hysteresis loops recorded by using the spectroscopic tool of piezoresponse force microscopy attest to the robustness of the piezoelectricity and ferroelectricity in these alpha-Pr2WO6 films. This study demonstrates the existence of a new lead-free ferroelectric material in the series of alpha-Ln2WO6 (lanthanide) tungstates, which can be considered as a promising candidate for applications in both nanoelectromechanical and energy-harvesting systems as well as for integrating optics.

An approach based on the use of a macromolecular coupling agent and the aim to improve the interfacial adhesion between piezoelectric ceramics and piezoelectric polymer matrix in piezoelectric composites is presented. Poly(methyl methacrylate) (PMMA) bearing a catechol moiety was used as a macromolecular coupling agent, as it is known to be miscible to piezoelectric fluoropolymers and catechol groups can strongly bind to a large variety of surfaces. Thus, entanglement between the PMMA chains and the amorphous segments of the fluoropolymer would ensure the desired interfacial adhesion. Well-defined PMMA was synthesized via RAFT polymerization using 2-cyano-2-propyl dodecyl trithiocarbonate as a chain-transfer agent. The PMMA omega-chain end was then functionalized with a catechol group via a one-pot aminolysis/thia-Michael addition procedure using a dopamine acrylamide (DA) derivative as a Michael acceptor. The presence of the catechol moiety at the chain end of PMMA was controlled by 1H NMR and cyclic voltammetry measurements. The resulting PMMA-DA was then grafted onto the surface of a lead-free piezoelectric ceramic film (i.e., a thin film of H2O2-activated (Bi0.5Na0.5)TiO3 (BNT) with a large contact area). The increase of the water contact angle confirmed the efficiency of the grafting. A commercial piezoelectric copolymer P(VDF-co-TrFE) was then spin-coated onto the modified BNT surface to form a bilayer composite. The composite cross section prepared by cryofracture was examined by scanning electron microscopy and revealed that the ceramic/polymer interface of the BNT-PMMA/P(VDF-co-TrFE) bilayer composite exhibits a much better cohesion than its counterpart composite prepared from nonmodified BNT. Moreover, the grazing incidence wide-angle X-ray scattering confirmed that the copolymer crystal structure was not impacted by the presence of the PMMA-DA coupling agent. A strong piezoelectric response was locally detected by piezoresponse force microscopy. This study highlights the potential of PMMA-DA as a macromolecular coupling agent to improve the ceramic/polymer interface in piezoelectric composite materials.

Large-area, conformal films of P(VDF-TrFE) and its spin-crossover composites were spray-coated. The films exhibit good crystallinity and attractive electromechanical properties over a thickness range of more than two decades.