Poled Films Research Articles

P‐192: Advancements in Photoaligned Azo‐Dye Thin‐Film Polarizer with Exceptional Dichroic Ratio

This study presents the development of ultra‐thin azo‐dye polarizers, notable for their minimal thickness (100‐200 nm) and superior optical performance, with polarization efficiency exceeding 99.9%, extinction ratios above 4000, transmittance over 45.3%, and dichoric ratio over 100. Utilizing cost‐effective solution‐processing methods, we fabricate these high‐performance polarizers and determine optimal experimental conditions for peak efficacy. Our research includes comprehensive Scanning Electron Microscopy analyses to understand the microstructural properties of these azo‐dye thin film polarizers, contributing significantly to the field of advanced display technologies.

Negative spin polarization of Mn2VGa Heusler alloy thin films studied in current-perpendicular-to-plane giant magnetoresistance devices

Negative spin polarization of Mn2VGa Heusler alloy thin films studied in current-perpendicular-to-plane giant magnetoresistance devices

A versatile method for exploring the magnetooptical properties of polar saturated and unsaturated ferromagnetic metallic thin films

Polar unsaturated ferromagnetic thin films are promising for low-power and high-speed nonvolatile resistive and optical memories. Here we measure the magnetooptical (MO) response of polar unsaturated Co90Fe10 and Co40Fe40B20 thin films in the spectral range from 400 nm to 1000 nm using vector MO generalized ellipsometry (VMOGE) in an out-of-plane applied magnetic field of ±0.4 T where magnetization of the ferromagnetic (FM) thin film is not saturated. Using magnetooptical simulation software (MagOpS®), we extract the complex MO coupling constant ( Q ) of the polar unsaturated FM thin films from difference spectra of VMOGE data recorded in a polar configuration at Hz = +0.4 T and Hz = −0.4 T. The presented approach opens a path to determine Q of both polar saturated and polar unsaturated FM thin films for simulating the MO properties of application-relevant optical memory multilayer structures.

Numerical study of concentration polarization of reverse osmosis film via the lattice Boltzmann method

The concentration polarization is the main factor affecting the water production rate of reverse osmosis. This article proposes a new numerical model based on the lattice Boltzmann method for simulating concentration polarization that can easily handle the computational instability caused by small diffusion coefficient. Based on this model, the concentration polarization in empty channel and unilateral spacer channel are simulated, respectively. The results show that the thickness of the CPL is generally about one tenth of the channel height. Increasing the Re can weaken concentration polarization, reduce the thickness of the CPL, and thereby increase permeate flux. Increasing the TMP can increase permeation flux, but it also accelerates the accumulation of solute increases the solute concentration within the CPL, and accelerates fouling. The spacer can effectively weaken the concentration polarization and increase permeate flux. But the unilateral spacer can cause uneven performance of the upper and bottom membranes.

D-π-A chromophores based on novel macroacceptors - Fused (azinylmethylene)malononitriles: Linear and nonlinear optical properties in solution and in poled polymer films

D-π-A chromophores based on novel macroacceptors − fused azinylmethylenemalononitriles (fused azine = pyrido [2,3-b]pyrazine, quinoline, quinoxaline and quinoxalin-2-one) − have been synthesized and their linear and nonlinear optical properties in gas, solution and in poled PMMA-based films have been investigated by DFT, UV–vis and second harmonic generation technique. The transition from chromophores with an azine acceptor to ones with azinylmethylenemalononitrile acceptors leads to a 10-fold increase in calculated μβ values. Poled polymer films doped with studied chromophores at 25 wt% load exhibit quadratic nonlinear optical activity with d33 values up to 42 pm/V.

Mid-infrared strong coupling between quasibound states in the continuum and epsilon-near-zero modes in a thin polar dielectric film

Mid-infrared strong coupling between quasibound states in the continuum and epsilon-near-zero modes in a thin polar dielectric film

Enhancement of remnant polarization in ferroelectric HfO2 thin films induced by mechanical uniaxial tensile strain after the crystallization process

The effect of strain on the ferroelectricity of HfO2 thin films after crystallization was investigated by applying uniaxial mechanical strains to Au/HfO2/TiN metal–ferroelectric–metal (MFM) capacitors. The remnant polarization (2P r) of MFM capacitors increased when tensile strain was applied during polarization switching. This phenomenon should not be attributed to phase transformation from the non-ferroelectric to the ferroelectric phase, taking account of the fast relaxation of 2P r after removal of the mechanical strain and the fact that the crystal structure of HfO2 thin films evaluated by grazing incidence X-ray diffraction measurement was not changed by the tensile strain.

Castor‐oil derived polyurethane/barium titanate piezoelectric smart composite coatings for energy harvesting applications: Prediction and experimental characterization of electro‐elastic properties

AbstractSustainable and environment‐friendly polymer composite smart paints/coatings with polyurethane (PU) derived from castor‐oil (CO) as the matrix and barium titanate (BTO) microparticles as piezo‐active inclusions (2, 4, 6, 8, and 10 vol.%) have been prepared employing ultrasonication and solvent casting, followed by contact DC poling method. Relative dielectric constants varied from 5.26 ± 0.37 for pristine COPU to 8.9 ± 0.36 for COPU/10 vol.% BTO composite, at a frequency of 1 kHz. Piezoelectric strain constant d33 of the poled films varied from 0.0 pC/N for pristine castor‐oil based polyurethane (COPU) to 1.2 pC/N for COPU/10 vol.% BTO (CPBT‐5) composite. Tensile tests showed that the elastic modulus varied from 1.98 ± 0.003 MPa for pristine COPU to 5.13 ± 0.02 MPa for COPU/10 vol.% BTO composite. Dynamic mechanical analysis confirmed the viscoelastic nature of the smart paints. Measurement of current–voltage response under different compressive loads indicates that COPU/10 vol.% BTO composite can generate a current of ~28 nA and voltage of ~8 V under a dynamic compressive load of 40 N, applied at a frequency of 1 Hz. These experiments were complemented by Fourier transform infra‐red spectroscopy and scanning electron microscopy. In addition, finite element analyses based on periodic boundary conditions have been performed to predict the effective electro‐elastic properties of these piezoelectric smart composite coatings.Highlights Castor‐oil‐based PU piezoelectric composites with BTO inclusions were developed. Increase in BTO content up to 10 vol.% increases dielectric constant by ~1.7 times. COPU/BTO composites exhibit significantly increased piezoelectric response. Elastic and viscoelastic properties are also enhanced with increasing BTO content. Finite element models show a good match with experimental results.

Magnetization switching by electric field in ZnFe2O4/ZnO heterostructure

We have fabricated the ZnFe2O4/ZnO (ZFO/ZnO) heterostructure on a silicon substrate by pulsed laser deposition technique and studied the magnetization switching by the electric field in the ZFO/ZnO heterostructure using an indigenously developed optical cantilever beam magnetometer setup. The magnetization (M) vs electric field (E) curve reveals that the magnetization of the ZFO film has been switched by an electric field applied along the thickness of the ZnO film. The saturation magnetization is found to be 28.77 MA/m from the M–E curve. The emergence of electric field-driven magnetization switching in the ZFO/ZnO heterostructure is attributed to the strain-mediated magnetoelectric coupling between the electric polarization of the ZnO film and the magnetization of the ZFO film as evidenced by the butterfly-type hysteresis behavior of magnetization with the applied electric field. However, the realization of electric field-controlled magnetization switching in the ZFO/ZnO heterostructure is regarded as a potential aspect for the fabrication of energy-efficient spintronic devices such as magnetoelectric random access memory cells, highly sensitive magnetic field sensors, magneto-logic devices, and neuromorphic devices.

Comparing Electrochemical Passivation and Surface Film Chemistry of 654SMO Stainless Steel and C276 Alloy in Simulated Flue Gas Desulfurization Condensates.

This research examines the behavior of electrochemical passivation and the chemistry of surface films on 654SMO super austenitic stainless steel and C276 nickel-based alloy in simulated condensates from flue gas desulfurization in power plant chimneys. The findings indicate that the resistance to polarization of the protective film on both materials initially rises and then falls with either time spent in the solution or the potential of anodic polarization. Comparatively, 654SMO exhibits greater polarization resistance than C276, indicating its potential suitability as a chimney lining material. Mott-Schottky analysis demonstrates that the density of donors in the passive film formed on 654SMO exceeds that on C276, potentially due to the abundance of Fe oxide in the passive film, which exhibits the characteristics of an n-type semiconductor. The primary components of the passive films on both materials are Fe oxides and Cr oxides. The formation of a thin passive film on C276 in the simulated condensates is a result of the low Gibbs free energy of nickel oxide and low Cr content. The slower diffusion coefficient of point defects leads to the development of a thicker and more compact passive film on the surface of 654SMO.

Surface effects for half-metallic Heusler alloy CrYCoAl

Magnetic tunnel junctions are the core component of spintronic devices, and good magnetic tunnel junctions require high tunnel resistance, which is determined by the spin polarization of the thin films of ferromagnetic layers that make up their structure. Therefore, the design of ferromagnetic films with high spin polarization is a current research hotspot in this field. In the current study, we taken the half-metallic CrYCoAl as an object, and studied the influence of surface effect on the half-metallic behavior. Especially, we constructed the CrYCoAl (100), (110), and (111) surfaces to study their stability, electronic and magnetic properties. Results show that the YY and YAl (100) surfaces, and Co (111) surface retain the half-metallic behavior and structural stability of bulk, which provide a basis for CrYCoAl application as a thin films in magnetic tunnel junctions thus, they are likely to be used in the spintronic devices.

Anomalous polarization-switching phenomena and noteworthy pyroelectricity in ferroelectric Hf0.5Zr0.5O2 polycrystalline films

Hafnia-based oxide thin films exhibit unconventional robust ferroelectricity at the nanoscale, paving the way for advancements in next-generation nanoelectronics. However, the stability and dynamics of ferroelectric polarization in hafnia-based oxides films, particularly at the nanoscale, warrant further exploration. In this study, we delve into the factors influencing the formation of the ferroelectric phase. Our findings illuminate that the confinement effect of the capped layer enhances the stabilization of the metastable orthorhombic phase, thereby bolstering its ferroelectricity and endurance. Furthermore, we identify an unprecedented polarization-switching behavior in HfO2-based ferroelectric films, characterized by a decrease in the remanent polarization and an increase in the coercive field as the temperature drops. This peculiar phenomenon can be ascribed to the reduction in the long-range interaction of polarization dipoles upon cooling, as evidenced by the dielectric spectrum. The diminished long-range interaction results in the emergence of nanodomains and a re-entrant relaxer behavior, offering novel insights into the origin of ferroelectricity and the stability of ferroelectric polarization in hafnia-based thin films. Given the commendable compatibility of Hf0.5Zr0.5O2 films with Si substrates and a pyroelectric coefficient of −62.1 μC/m2·K, they emerge as a prime candidate for sensor device applications.

Effects of Mn doping on the conduction mechanism and dielectric nonlinearity of Na0.5Bi0.5TiO3 thin film

In this work, the conduction mechanism and dielectric nonlinearity of undoped and Mn-doped Na0.5Bi0.5TiO3 (NBT) films were investigated. The potential conduction mechanism in relatively low electric fields should be dominated by hopping conduction rather than typical Ohmic conduction. In the high electric field region, the conduction mechanism is dominated by Poole–Frenkel emission and Schottky emission. The enhancement of electrical insulation of NBT films after Mn doping was shown to result from a decrease in oxygen vacancies and elevation of the conduction energy barrier. Furthermore, significant improvements in the nonlinearity of both the dielectric constant and polarization of Mn-doped NBT films were observed, as indicated by the results of Rayleigh fitting and first-order reversal curve distributions. Such enhancements were attributed to the reduction in domain wall pinning, decreased interference from electrostatic potential and improved leakage characteristics.

Observing ferroelastic switching in Hf0.5Zr0.5O2 thin film

Abstract Hafnium zirconium oxides (HZO), which exhibit ferroelectric properties, are promising materials for nanoscale device fabrication due to their high CMOS compatibility. In addition to piezoelectricity, ferroelectricity, and flexoelectricity, this study reports the observation of ferroelasticity using piezoelectric force microscopy (PFM) and scanning transmission electron microscopy (STEM). The dynamics of 90° ferroelastic domains in HZO thin films are investigated under the influence of an electric field. Switching of the retentive domains is observed through repeated wake-up measurements. This study presents a possibility of enhancing polarization in HZO thin films during wake-up processes.

An effective microwave absorber using multi-layer Design of carbon allotrope based Co2Z hexaferrite-Polymer nanocomposite film for EMI shielding applications

This report shows impressive electromagnetic interference (EMI) shielding efficiency of laminated nanocomposites of PVDF containing binary nanofillers of rGO and Co2Z hexaferrite. These rGO layers in the PVDF matrix in association with magnetic nanofillers have been considered to improve interfacial polarization by accumulating charges at the interfaces of rGO-Co2Z hexaferrite-PVDF system. The crystallographic phase, chemical composition, and successful incorporation of the binary nanofillers into PVDF have been verified using XRD, XPS, RAMAN, and FESEM analysis. The J-E analysis of rGO-Co2Z hexaferrite-PVDF nanocomposite films confirm that the current density of all the nanocomposite films is very less and found in the order of 10-5 A/m2 under the maximum electric field of 70 kV/m. This indicates the emergence of polarization effect in the nanocomposite films when subjected to high external electric field without having electrical breakdown. The significant magnetization of ∼8.9 emu/g for nanocomposite films, at room temperature is beneficial for boosting the EMI shielding effectiveness due to absorption (SEA). The combination of magnetization and electrical polarization in nanocomposite film helps to attain significantly high total shielding effectiveness (SET) in the frequency range of 12–18 GHz. The shielding effectiveness study of both mono-layer and multi-layer nanocomposite films have been investigated. Improvement of SEA has also been achieved by the elevation of the thickness of the nanocomposite film within the range of 0.8 to 1.0 mm, which in turn improves SET to a value of −54.09 dB at 15.70 GHz for multi-layer system of thickness 0.861 mm with >99.999 % of attenuation whereas the mono-layer film of thickness 0.180 mm shows the SET of −47.03 dB at 14.76 GHz with an attenuation of >99.99 %.

Ferroelectric polarization and conductance filament coupling for large window and high-reliability resistive memory and energy-efficient synaptic devices

Ferroelectric capacitors hold great promise for non-volatile memory applications. However, the challenge lies in fabricating resistive switching devices with a high on/off ratio, excellent non-volatility, and a simple manufacturing process. Here, a novel approach is introduced by demonstrating the efficacy of the coupling effect between ferroelectric polarization and oxygen vacancy-based conductive filaments in Hf0.5Zr0.5O2 (HZO) films for the creation of non-volatile resistive switching memory devices, achieving an impressive on/off ratio of 6.8 × 103 at +1.8 V. An in-depth exploration of the resistive switching mechanism is provided and subsequently the outstanding durability and retention characteristics of these devices for resistive switching is validated. Furthermore, the device’s capacity to emulate non-volatile synaptic functionalities is assessed. Our results reveal that under pulsed conditions of 1 V/–2 V with 1 µs pulses spaced 50 ms apart, the device can robustly achieve potentiation/depression synaptic plasticity, while exhibiting energy consumption (0.16 fJ for potentiation, 0.12 fJ for depression) reduced by 1–2 orders of magnitude compared to biological synapses. This work holds significant value as a reference for the fabrication of energy-efficient, non-volatile memory and synaptic devices.

Ferroelectric and electric field cycling properties of un-doped HfO2 films

As the most promising candidate material for nonvolatile memories, premature occurrence of fatigue phenomenon for ferroelectric HfO2 film has no appropriate solution method. In this paper, HfO2/Y/HfO2 films were deposited with reactive magnetron sputtering and realized ferroelectric property after wake-up process even if without doping and post-metallization annealing (PMA). Different with uniform or symmetrical distribution, oxygen vacancies concentrated in the film middle, resulting in a longer migration path and tardy fatigue. Fatigue appeared after the electric field cycling of 109 in HfO2 film inserted with 0.6 nm metal Y, which is obviously higher than films deposited by other methods. The remanent polarization of un-doped HfO2 films inserted with 0.6 and 1.5 nm metal Y interlayer is 11.8 and 14.8 μC/cm2, respectively. The results provide a method for to improve cycling property and confirm the important role of oxygen vacancies in wake-up and fatigue phenomenon for HfO2 films.

Reversible Optical Control of Polarization in Epitaxial Ferroelectric Thin Films.

Light is an effective tool to probe the polarization and domain distribution in ferroelectric materials passively, that is, non-invasively, for example, via optical second harmonic generation (SHG). With the emergence of oxide electronics, there is now a strong demand to expand the role of light toward active control of the polarization. In this work, optical control of the ferroelectric polarization is demonstratedin prototypical epitaxial PbZrx Ti1-x O3 (PZT)-based heterostructures. This is accomplished in three steps, using above-bandgap UV light, while tracking the response of the polarization with optical SHG. First, it is found that UV-light exposure induces a transient enhancement or suppression of the ferroelectric polarization in films with an upward- or downward-oriented polarization, respectively. This behavior is attributed to a modified charge screening driven by the separation of photoexcited charge carriers at the Schottky interface of the ferroelectric thin film. Second, by taking advantage of this optical handle on electrostatics, remanent optical poling from a pristine multi-domain into a single-domain configuration is accomplished. Third, via thermal annealing or engineered electrostatic boundary conditions, a complete reversibility of the optical poling is further achieved. Hence, this work paves the way for the all-optical control of the spontaneous polarization in ferroelectric thinfilms.

Nanosecond laser damage of 532 nm thin film polarizers evaluated by different testing protocols

Different laser damage testing protocols, including 1-on-1, S-on-1, and Raster Scan, were conducted on 532 nm polarizers to evaluate the damage resistance and mechanisms. A comparison of the laser-induced damage thresholds (LIDTs) revealed different damage characteristics and major contributions to film failure for different polarizations. For P polarization, the LIDTs for the three test protocols were nearly the same because of the stabilization of two typical damage morphologies of flat-bottomed pits and mussel damage pits. For S polarization, the LIDTs for multiple pulses were lowest, where absorptive defect-induced damage was revealed. The damage characteristics of 532 nm polarizers and 1064 nm polarizers have been also compared. The mussel damage pits, which are similar to the typical damage morphologies of ultraviolet (UV) laser damage to fused silica, were observed for the first time in coatings of 532 nm polarizers. This suggests that, the polishing-induced subsurface damage of fused silica substrates may tend to be excited by a short-wavelength laser rather than the fundamental wavelength.

Enhancing performance of polar InGaN-based thin film solar cells through intrinsic layer impact optimization: Numerical modeling

The paper deals with the conception and feasibility of the device structure based on the optimized PIN-(In, Ga)N homojunction solar cells. A new and efficient model combining the most realistic ones considering the impacts of band gap narrowing, collection efficiency, Shockley-Read-Hall recombination, and interface polarization is proposed to examine the solar cells' performance numerically. The functioning processes of n-In0.42Ga0.58N/i-(In, Ga)N/p-In0.42Ga0.58N solar cells at room temperature were investigated by calculating their characteristics for the AM1.5D, AM1.5G, and AM0 American Society for Testing and Materials experimental data. Our results show that the indium content, thickness, and defect density of the intrinsic layer strongly influence the characteristics of the InGaN solar cells. As the In-mole fraction increases, Voc, FF and efficiency diminish to reach an independent regime for high In-content. A higher-quality 2μm−In0.43Ga0.57N for 1014cm−3 defect concentration can exhibit as high an efficiency as ≅11.3%, dropping to ≅4.12% for 1016cm−3 one.