Bilayer Films Research Articles

Electrochemical deposition of coloured Ni/Cu2O bilayer films on large area plastic substrates for decorative applications

ABSTRACT In this study, coloured Ni/Cu2O bilayer films were electrochemically deposited on large area automobile plastic parts (7 × 13 cm) for decorative applications. Such coatings may become an alternative to ubiquitously used Cr coatings for plastics. Purple, dark cyan and gold colours with good homogeneity and high brightness could be produced by tuning the deposition time of the Cu2O layer. Colouration of the bilayer film can be ascribed to interference of light through the metal/dielectric layer, where the thickness of the dielectric layer controls the wavelength of the reflected light. Cu2O film has a compact structure and low roughness, which is essential to obtain uniform colours. Moreover, the Ni/Cu2O bilayer exhibits good adhesion behaviour, environmental stability and enhanced corrosion resistance. This process is industrially viable and enables the large scale production of such decorative coatings.

Biodegradable monolayer film based on the collagen extracted from Oreochromis sp. processing byproducts blended with chitosan and assembled with PCL and PLA monolayers to form bilayers films

AbstractThe objective of the study is to develop and characterize biodegradable monolayer and bilayer films using collagen extracted from tilapia skin and scales (Oreochromis sp.) with chitosan in combination with biodegradable polyester; polylactic acid (PLA) or polycaprolactone (PCL). Collagen extraction was conducted with acetic acid (0.5 M). Monolayer films based on collagen and chitosan were formed by the casting process with a solution of chitosan (2% w/w) in 1.5% acetic acid, followed by the addition of skin collagen at concentrations of 0.5%, 1%, or 2% w/w, and dried at 45–50°C. The PLA and PCL films were made by compression molding. The films were characterized according to their appearance, structure, morphology, interaction with water, thermal stability, and mechanical and barrier properties. The results indicated that collagen from tilapia skin and scales yielded 36.5% and 2.57%, respectively. The results showed that adding chitosan increased the tensile strength but decreased the elongation of the films. An improvement in thermal stability was observed by increasing the proportion of collagen or chitosan, and it also influenced water solubility and water vapor permeability. Microscopy showed a crack‐free interface between collagen and chitosan. The color of the films varied depending on the composition, highlighting the influence of chitosan in yellow and reddish tones. The bilayers with PLA had lower water vapor permeability and higher gloss compared to those with PCL. Finally, the developed films showed promising properties for their application in food packaging and promote the use of fishery waste.Practical applicationsThe study aims to develop and characterize biodegradable monolayer and bilayer films using collagen extracted from tilapia skin and scales (Oreochromis sp.) combined with chitosan and biodegradable polyester such as polylactic acid or polycaprolactone. The practical applications of this research span a wide range of industrial fields. For instance, monolayer films could be used as sustainable food packaging, offering enhanced barrier properties and biodegradability, thus reducing the environmental impact of conventional packaging. Furthermore, bilayer films could find applications in the healthcare industry, such as controlled‐release drug patches or dressings leveraging the antimicrobial properties of chitosan. This research also provides valuable insights into improving the mechanical, thermal, and barrier properties of biodegradable films, potentially leading to the production of more efficient and versatile materials for a variety of industrial applications.

Fabrication of a hot mirror using ITO-free electrochromic films

In this study, WO3/Ag/W/WO3 (WAWW) films were deposited at room temperature on a B270 glass substrate from W and Ag targets using a radiofrequency magnetron reactive sputtering system. The influence of the thin tungsten interlayer on the electrical and optical properties of the WAWW layer structure was investigated through ellipsometry, a four-point probe and a spectrophotometer. It was determined that the thin tungsten interlayer effectively prevented the oxidation of the silver film. The WAWW film had a dielectric-metal-dielectric (DMD) layered structure with good electrical conductivity and high visible transmittance. The tungsten layer was no more than 2-nm thick. The sheet resistance and luminous transmittance of the WO3(29.5 nm)/Ag(14.2 nm)/W(2 nm)/WO3(68.6 nm) film were 4.64 Ω/sq and 65.4 %, respectively. Based on the WAWW four-layer structure, stacked WO3(29.5 nm)/Ag(14.2 nm)/W(2 nm)/WO3(68.6 nm)/Ag(16.9 nm)/W(2 nm)/WO3(30.4 nm) seven-layer structures deposited on B270 glass substrates were used for both ITO-free electrochromic and hot mirror applications. The visible (400–700 nm) and NIR (700–1200 nm) transmittance values of the bleached WAWW seven-layer structure were 71.5 % and 9.9 %, respectively. The visible transmittance of the colored WAWW seven-layer structure was 23.6 %. Finally, the bi-layer WAWW films were used to obtain an ITO-free WAWW seven-layer structure with a good electrochromic and optical performance.

Effect of nickel oxide concentration on titanium oxide bilayer photoanode for dye-sensitized solar cell application

The mesoporous titanium oxide has attracted significant attention as a photoanode material for Dye-Sensitized Solar Cells (DSSCs). In the present work, we coated a planar NiO layer on the TiO2 film to minimize charge recombination with the dye and/or electrolyte molecules. The structural, morphological, elemental, optical, and electrical properties of the TiO2 and bi-layered TiO2/NiO films were studied using various characterization techniques. DSSCs based on N3 dye-sensitized TiO2 and bi-layered TiO2/NiO films were fabricated using PI as the redox electrolyte. The photocurrent density–voltage (J–V) characteristics of the DSSCs were studied using a solar simulator. Various parameters, such as open-circuit voltage (Voc), short-circuit photocurrent density (Jsc), and fill factor (FF), were calculated from the J–V characteristics. DSSCs based on bi-layered TiO2/NiO films showed superior performance compared to bare TiO2 films. The J–V characteristics of bilayer film shows enhanced open-circuit voltage (Voc) ~ 0.56 V, short-circuit current density (Jsc) ~ 2.14 mA/cm2, fill factor (FF) ~ 75%, and efficiency (ƞ) ~ 0.91%. The TiO2/NiO solar cell showed a ~ 28% increase in efficiency compared to TiO2-based DSSC. Hence, the bi-layered TiO2/NiO films have potential applications in optoelectronic and photovoltaic devices.

Structural optimization of ion storage layer for highly stable electrochromic devices based on polythiophene derivative films

Due to their rich color, fast switching speed and high coloration efficiency, polymer-based electrochromic devices (ECDs) have broad application prospects in various fields such as smart windows, anti-glare rearview mirrors, displays and adaptive camouflage. However, the preparation of highly stable polymer-based ECDs is still a great challenge. Herein, we present a simple and efficient strategy to construct the poly (3,4-ethylenedioxythiophene) (PEDOT)-multi-walled carbon nanotubes (MWCNTs) composite film or PEDOT/MWCNTs bilayer film, which serves as ion storage layer. The ECDs are assembled with poly (3-hexylthiophene) (P3HT) as EC layer due to its good EC behavior. The P3HT film was prepared by potentiostatic deposition, and the PEDOT, PEDOT-MWCNTs and PEDOT/MWCNTs films were obtained by spray-coating technology. We investigated the structure, morphology and electrochemical performance of P3HT, PEDOT, PEDOT-MWCNTs and PEDOT/MWCNTs films, and EC properties of devices. The results indicate that the rough and porous P3HT film consists of many nanoparticles. Compared with PEDOT-MWCNTs composite film, the PEDOT/MWCNTs film is more loose and porous, where PEDOT nanoparticles and some PEDOT nanosheets are coated on a three-dimensional skeleton film of MWCNTs. These films possess good electrochemical performance. The ECD based on P3HT and PEDOT/MWCNTs films achieves an optical contrast of 38 % and coloration efficiency of 375 cm2/C, exhibiting good cyclic stability (retaining 92 % of initial optical contrast after 2000 cycles). Its coloration time and bleaching time are 0.60 and 1.83 s, respectively. This study suggests that structural optimization of ion storage layer might be a facile strategy for fabricating highly stable polymer-based ECDs.

Biodegradation of PHB/PBAT films and isolation of novel PBAT biodegraders from soil microbiomes

Polyhydroxyalkanoates (PHAs) are important candidates for replacing petroleum-based plastics. This transition is urgent for the development of a biobased economy and to protect human health and natural ecosystems. PHAs are biobased and biodegradable polyesters that when blended with other polymers, such as poly(butylene adipate-co-terephthalate) (PBAT), acquire remarkable improvements in their properties, which allow them to comply with the requirements of packaging applications. However, the biodegradation of such blends should be tested to evaluate the impact of those polymers in the environment. For instance, PBAT is a compostable aliphatic-aromatic copolyester, and its biodegradation in natural environments, such as soil, is poorly studied. In this work, we evaluated the biodegradation of a bilayer film composed of PHB and PBAT, by a soil microbiome.The bilayer film reached 47 ± 1 % mineralization in 180 days and PHB was no longer detected after this period. The increased crystallinity of the PBAT residue was a clear sign of biodegradation, indicating that the amorphous regions were preferentially biodegraded. Seven microorganisms were isolated, from which 4 were closely related to microorganisms already known as PHB degraders, but the other 3 species, closely related to Streptomyces coelicoflavus, Clonostachys rosea and Aspergillus insuetus, were found for the first time as PHB degraders. Most remarkably, two fungi closely related to Purpureocillium lilacinum and Aspergillus pseudodeflectus (99.83 % and 100 % identity by ITS sequencing) were isolated and identified as PBAT degraders. This is very interesting due to the rarity of isolating PBAT-degrading microorganisms.These results show that the bilayer film can be biodegraded in soil, at mesophilic temperatures, showing its potential to replace synthetic plastics in food packaging.

Damage-free dry transfer method using stress engineering for high-performance flexible two- and three-dimensional electronics.

Advanced transfer printing technologies have enabled the fabrication of high-performance flexible and stretchable devices, revolutionizing many research fields including soft electronics, optoelectronics, bioelectronics and energy devices. Despite previous innovations, challenges remain, such as safety concerns due to toxic chemicals, the expensive equipment, film damage during the transfer process and difficulty in high-temperature processing. Thus a new transfer printing process is needed for the commercialization of high-performance soft electronic devices. Here we propose a damage-free dry transfer printing strategy based on stress control of the deposited thin films. First, stress-controlled metal bilayer films are deposited using direct current magnetron sputtering. Subsequently, mechanical bending is applied to facilitate the release of the metal bilayer by increasing the overall stress. Experimental and simulation studies elucidate the stress evolution mechanisms during the processes. By using this method, we successfully transfer metal thin films and high-temperature-treated oxide thin films onto flexible or stretchable substrates, enabling the fabrication of two-dimensional flexible electronic devices and three-dimensional multifunctional devices.

Analysing the surface morphology of annealed FTO/ZnS bilayer films: stereometric, fractal, and wettability approaches

The surface micromorphology and roughening of the thermal evaporation-coated FTO/ZnS bilayer thin films annealed at 300, 400, 500, and 550∘C\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$550\\,^\\circ{\ ext{C}}$$\\end{document} for 1 h have been studied. AFM images of the prepared samples were analysed by the MountainsMap software, and the effects of the annealing temperature on the surface texture of the FTO/ZnS thin film’s surface were investigated. Stereometric and advanced fractal analyses showed that the sample annealed at 500∘C\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$500\\,^\\circ{\ ext{C}}$$\\end{document} exhibited greater surface roughness and greater skewness and kurtosis. This film also has the most isotropic surface and exhibits the highest degree of heterogeneity. Also, despite the decrease in surface roughness with increasing temperature from 500 to 550∘C\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$550 \\,^\\circ{\ ext{C}}$$\\end{document}, the fractal dimension tends to increase. The static water contact angle measurements indicate that the film annealed at 500∘C\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$500 \\,^\\circ{\ ext{C}}$$\\end{document} exhibits higher hydrophobicity, which can be attributed to its greater topographic roughness. Our research indicates that the surface morphology of FTO/ZnS bilayer thin films is influenced by the annealing temperature. Changing factors such as roughness, fractality, and wettability parameters to help improve surface performance make the FTO/ZnS bilayer suitable for application in electronic and solar systems.

Curvature-Insensitive Transparent Surface-Enhanced Raman Scattering Substrate Based on Large-Area Ag Nanoparticle-Coated Wrinkled Polystyrene/Polydimethylsiloxane Film for Reliable In Situ Detection.

Flexible and transparent surface-enhanced Raman scattering (SERS) substrates have attracted considerable attention for their ability to enable the direct in situ detection of analytes on curved surfaces. However, the curvature of an object can impact the signal enhancement of SERS during the measurement process. Herein, we propose a simple approach for fabricating a curvature-insensitive transparent SERS substrate by depositing silver nanoparticles (Ag NPs) onto a large-area wrinkled polystyrene/polydimethylsiloxane (Ag NP@W-PS/PDMS) bilayer film. Using rhodamine 6G (R6G) as a probe molecule, the optimized Ag NP@W-PS/PDMS film demonstrates a high analytical enhancement factor (AEF) of 4.83 × 105, excellent uniformity (RSD = 7.85%) and reproducibility (RSD = 3.09%), as well as superior mechanical flexibility. Additionally, in situ measurements of malachite green (MG) on objects with diverse curvatures, including fish, apple, and blueberry, are conducted using a portable Raman system, revealing a consistent SERS enhancement. Furthermore, a robust linear relationship (R2 ≥ 0.990) between Raman intensity and the logarithmic concentration of MG detected from these objects is achieved. These results demonstrate the tremendous potential of the developed curvature-insensitive SERS substrate as a point-of-care testing (POCT) platform for identifying analytes on irregular objects.

Preparation of bi-layer composite films for controlled cefazolin delivery and enhanced antibacterial activity

In the present study, a wide-spectrum antibiotic drug, cefazolin was loaded into novel bi-layer composite films based on chitosan and alginate. The objective was to achieve sustained antibacterial activity at the application site, while enhancing the local efficacy of cefazolin. The physical properties of the composite films were characterized using techniques including FTIR, XRD, and SEM. Additionally, drug content uniformity, contact angle, weight variation, swelling index, drug release profiles, and kinetics were investigated. Antibacterial efficacy of the films was evaluated against Methicillin-resistant Staphylococcus aureus (MRSA), an important drug resistant pathogen. Multiple assays including time-kill, disk diffusion, and microbial penetration assays were employed to comprehensively assess various parameters of antibacterial action. The results demonstrated homogenous drug distribution and minimal weight variation in the films. Well-compatible film formations were shown by the SEM micrographs. Cefazolin release was sustained for 1440 min, and the release kinetics were fitted with the Korsmeyer-Peppas model. The fabricated films exhibited significant and sustained antibacterial activity against MRSA for a duration of 900 minutes, ultimately leading to complete eradication of viable bacterial populations. Taken together, novel films demonstrated good mechanical properties and hold great promise for biomedical applications, offering extended antibiotic release and sustained pathogen eradication.

Ion Beam-Induced modification in the optical properties of the bilayer of nano-structured amorphous selenium and multi-walled carbon Nanotubes: A study by 70 MeV Ni Ions

In this study, we report improved physical properties of selenium with multi-walled carbon nanotubes (MWCNTs) resulting from a homogeneous mixture of CNT-Se bi-layer thin film by using swift heavy ion irradiation. FESEM micrographs clearly showed the inter-diffusion of Se nanoparticles into MWCNTs following swift heavy ion (SHI) irradiation, EDX validates the elemental composition. The existence of different phonon modes (LO mode and D, G, G' bands) has been found in the Raman spectra of the investigated bi-layer thin films. UV–Visible spectroscopic analysis of pristine CNT-Se thin films show two sharp absorption edges at ∼670 nm and ∼340 nm. After swift heavy ion irradiation, the sharp absorption edge at ∼670 nm exhibits a blue shift, whereas the absorption edge at ∼340 nm exhibits a red shift, confirming the homogeneous mixing of two layers. These remarkable shifts found in the optical properties of CNT-Se bi-layer make the investigated material feasible for many optoelectronic device applications.

Permeability of triamcinolone acetonide, released from mucoadhesive films, through a buccal mucosa-mimetic barrier: Permeapad™

ObjectivesThe permeability of triamcinolone acetonide (TA), from bilayer mucoadhesive buccal films, through a biomimetic membrane, Permeapad™, was investigated employing Franz diffusion cell. The delivery systems composition and ethyl cellulose (EC) backing layer, on drug permeability, were assessed. MethodsThree TA-loaded films were tested; hydroxypropyl methylcellulose (HPMC K4M; bilayer [F1] and monolayer), HPMC K4M/Polyvinylpyrrolidone (PVP): 90/10 [F2], and HPMC K15M film [F3]. All films contained propylene glycol (PG-plasticiser). TA solution alone was used as a control. TA permeability via a Permeapad™ barrier, simulating buccal mucosa, was assessed over 8 h using a Franz diffusion cell. TA permeated into the receptor compartment, released in the donor compartment, and located on/within the Permeapad™ barrier were analysed using UV-spectrophotometer. Results45.7 % drug retention within the Permeapad™ barrier was delivered from F1 (highest). F1, F2, and F3 significantly improved the TA’s permeability through Permeapad™, compared to TA solution alone (e.g., 8.5 % TA-solution, 21.5 %-F1), attributed to the synergy effect of HPMC and propylene glycol acting as penetration enhancers. F1 displayed a significant increase in drug permeability (receptor compartment; 21.5 %) compared to F3 (17.0 %). PVP significantly enhanced drug permeability (27.5 %). Impermeable EC backing layer controlled unidirectional drug release and reduced drug loss into the donor compartment (e.g., ∼28 % for monolayer film to ∼10 % for bilayer film, F1). SignificanceThe mucoadhesive films demonstrated improved TA permeability via Permeapad™. The findings suggest that these bilayer mucoadhesive films, particularly F1, hold promise for the effective topical treatment of oral mucosa disorders, such as recurrent aphthous stomatitis and oral lichen planus.

Multifunctional and edible egg white/amylose-tannin bilayer film for perishable fruit preservation

The substantial waste of perishable foods during transportation significantly contributes to greenhouse gas emissions, intensifying the climate crisis. To mitigate the rapid spoilage of fruits, an eco-friendly bilayer film was developed using natural egg white (EW), amylose (Am), and tannic acid (TA). The EW/Am-TA bilayer film features a primary layer of amphiphilic EW, ensuring a uniform coating on hydrophobic fruit surfaces, and a secondary layer composed of Am and TA, imparting notable tensile strength (5.3 ± 0.5 MPa) and elongation at break (28.5 ± 4.1 %). This bilayer film effectively shields fruits from UV-B and UV-C radiation (~0 % transmittance at 280 and 330 nm) and exhibits antioxidant and antibacterial properties due to the presence of TA. Fruits such as bananas, avocados, and cherry tomatoes, when dip-coated with the optimized EW/Am-TA bilayer, maintained their freshness, color, weight, and texture for up to seven days, demonstrating the effectiveness of this bilayer coating in food preservation. The natural materials in the coated film are edible and can be safely removed with tap water at room temperature in <10 s, posing no food safety risks. Thus, the proposed bilayer coating presents a significant solution to the global problem of food waste.

Electrochemical polymerization of polyaniline/single-walled carbon nanotube bilayer films with enhanced thermoelectric properties

In this work, polyaniline (PANI) is coated on single-walled carbon nanotubes (SWCNT) via electrochemical polymerization method to fabricate PANI/SWCNT bilayer films with enhanced thermoelectric properties. Effects of deposition time and voltage, and acid types and concentrations on the thermoelectric properties of the films are studied. The results showed that PANI layer was effectively coated on the surface of SWCNT layer by electrochemical polymerization method. In addition, carrier transport and the electrical conductivity (σ) of the PANI/SWCNT bilayer film was improved due to interfacial π-π interaction between PANI and SWCNT, and the Seebeck coefficient (S) was increased due to the energy filtering effect at the interface of PANI/SWCNT. The maximum PF of PANI/SWCNT at room temperature was 155.3 ± 7.2 μW m−1 K−2 with the σ of 654.9 ± 41.8 S cm−1 and the S of 48.7 ± 0.5 μV K−1 when the deposition voltage and time were 1.0 V and 240.0 s using 0.5 M HCl, respectively. Finally, a self-powered thermoelectric device composed of five pairs of p-n junctions was prepared with PANI/SWCNT (1 V, 240 s) as the p-type legs and copper adhesives as the n-type legs, and the maximum output power was 0.27 μW at a temperature difference of 50 K. Therefore, this demonstrates that electrochemical polymerization is a feasible and effective way of fabricating conductive polymers/carbon nanotubes bilayer films with enhanced thermoelectric properties, which have potential application in powering wearable electronics.

Smart bilayer film: Quality monitoring for freshness of fish and minced pork delights

Global concern over food spoilage and the pressing need for efficient spoilage detection methods have far-reaching implications for the well-being of millions of people worldwide. So, the emergence of systems capable of providing early detection and visible evidence of food spoilage has gained recognition as an essential tool in the fight against food spoilage. A smart bilayer label (SBL) was developed, which exhibits distinctive qualities, encompassing robust antioxidant and antimicrobial characteristics, responsive color alteration triggered by minor pH fluctuations, and the capability to exhibit color changes upon exposure to acetic acid and ammonia gas. The SBL shows robustness regarding mechanical, thermal, and barrier properties, including water and oxygen resistance and overall hydrophilicity. The ability of SBL to detect the freshness of fresh fish and minced pork at 6 °C was determined. Over time, for both fish and pork, an increase in pH, total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS), and total viable counts (TVC) were detected. Notably, SBL changed to green on days 8 and 10 for fish and minced pork, respectively, corresponding to pH ranges of 7, indicating spoilage. This study validates the SBL as an effective freshness indicator, with a color change discernible to the naked eye (ΔE > 12), and highlights its potential for monitoring the quality of protein-rich products. Strong positive correlations between pH, TVB-N, TVC, and storage time underscore their interdependence (P < 0.01). The SBL’s ΔE positively correlates with pH, TVB-N, and TVC, affirming its effectiveness as a visual freshness indicator. These insights advance our understanding of the evolution of meat quality and endorse the SBL's role in real-time monitoring and enhancing meat industry practices.

Two comparative novel facile synthesis of Prussian blue/polyaniline bilayer films for supercapacitor electrode

A nanocomposite films of Prussian Blue/Polyaniline were prepared on ITO without binder, by two procedures: The first by forming thin multi layers of films of Prussian blue and Polyaniline alternatively, up to seven utilizing “layer by layer” technique. To prepare another film, a thick layer of Prussian Yellow was made under a Polyaniline layer with almost the same load of materials.PB successive layers were fabricated by dipping the ITO in a mixture of (Fe (NO3)3 + K3Fe(CN)6) solution, for a few minutes. next Pani layers were overlayed by electropolymerizing of aniline solution on the ITO/PY electrode. PY instantly was reduced by aniline as soon as dipped in solution, resulting in a nano Prussian Blue film on ITO.Uv-vis and FT-IR spectroscopy were used to characterize the fabricated films. AFM and SEM were utilized to study its morphology. The capacitive behavior of the two types of films was studied utilizing CVs and GCD techniques. The resistance of the electrode/electrolyte interface was studied by EIS. The electrochemical analysis confirmed that the multi-layer by layer thin film has much-improved specific capacitance of 255.6 F/g at 1 A/g current density and superior stability of 96.4 % of its initial value after 500 cycles.

Enhanced energy storage performance in Ag(Nb,Ta)O3 films via interface engineering

Dielectric capacitors with ultrahigh power density and ultra-fast charge/discharge rate are highly desired in pulse power fields. Environmental-friendly AgNbO3 family have been actively studied for its large polarization and antiferroelectric nature, which greatly boost the electric energy storage performance. However, high-quality AgNbO3-based films are difficult to fabricate, leading to a low breakdown field Eb (<1.2 MV/cm) and consequently arising inferior energy storage performance. In this work, we propose an interface engineering strategy to mitigate the breakdown field issue. A Ag(Nb,Ta)O3/BaTiO3 bilayer film is proposed, where the BaTiO3 layer acts as a p-type semiconductor while Ag(Nb,Ta)O3 layer is n-type, together with the n-type LaNiO3 buffer layer on the substrate, forming an n-p-n heterostructure. The n-p-n heterostructure elevates the potential barriers for charge transport, greatly reducing the leakage current. An extremely large breakdown field Eb∼4.3 MV/cm is achieved, being the highest value up to date in the niobate system. A high recoverable energy density Wrec∼62.3 J/cm3 and a decent efficiency η∼72.3% are obtained, much superior to that of the Ag(Nb,Ta)O3 monolayer film (Wrec∼46.4 J/cm3 and η∼80.3% at Eb∼3.3 MV/cm). Our results indicate that interface engineering is an effective method to boost energy storage performance of dielectric film capacitors.

Comparative Study of Plasma-Enhanced-Atomic-Layer-Deposited Al2O3/HfO2/SiO2 and HfO2/Al2O3/SiO2 Trilayers for Ultraviolet Laser Applications.

High-performance thin films combining large optical bandgap Al2O3 and high refractive index HfO2 are excellent components for constructing the next generation of laser systems with enhanced output power. However, the growth of low-defect plasma-enhanced-atomic-layer-deposited (PEALD) Al2O3 for high-power laser applications and its combination with HfO2 and SiO2 materials commonly used in high-power laser thin films still face challenges, such as how to minimize defects, especially interface defects. In this work, substrate-layer interface defects in Al2O3 single-layer thin films, layer-layer interface defects in Al2O3-based bilayer and trilayer thin films, and their effects on the laser-induced damage threshold (LIDT) were investigated via capacitance-voltage (C-V) measurements. The experimental results show that by optimizing the deposition parameters, specifically the deposition temperature, precursor exposure time, and plasma oxygen exposure time, Al2O3 thin films with low defect density and high LIDT can be obtained. Two trilayer anti-reflection (AR) thin film structures, Al2O3/HfO2/SiO2 and HfO2/Al2O3/SiO2, were then prepared and compared. The trilayer AR thin film with Al2O3/HfO2/SiO2 structure exhibits a lower interface defect density, better interface bonding performance, and an increase in LIDT by approximately 2.8 times. We believe these results provide guidance for the control of interface defects and the design of thin film structures and will benefit many thin film optics for laser applications.

Polarization characteristics of Ni/Pt-based spintronic terahertz emitters based on spin electron dynamics

We report on the terahertz (THz) emission polarization characteristics of spintronic nickel/platinum (Ni/Pt) bilayer films. The films were deposited on MgO substrates via electron beam deposition with varying Ni thicknesses of 5, 7, and 9 nm and a constant Pt thickness of 6 nm. Results from B-field polarity-dependent THz measurements exhibited different THz emission characteristics for the p- and s-polarized components. We attribute the strong, wide-bandwidth B-field dependent p-polarized component to the inverse spin Hall effect and the weak, low-bandwidth B-field independent s-polarized component to the ultrafast demagnetization process. The peak-to-peak THz emission amplitudes were demonstrated to be dependent on the sample rotational angle about the optical axis which suggests sample inhomogeneity from the deposited Ni/Pt spintronic films. These results are crucial for the material design and development of more intense spintronic THz sources.

Energy storage and dielectric properties in PbZrO3/PbZrTiO3 antiferroelectric/ferroelectric bilayer bulk structure using Landau theory

Employing Landau theory and the Landau–Khalatnikov (L–K) equation of motion, we investigate the phase transitions in individual layers of antiferroelectric lead zirconate (PbZrO3), ferroelectric lead zirconate titanate (PbZrTiO3), and an antiferroelectric/ferroelectric PbZrO3/PbZr(0.21)Ti(0.79)O3 bilayer bulk structure. We examine the dielectric hysteresis loop behavior of the three systems, with a specific focus on the PbZrO3/PbZr(0.21)Ti(0.79)O3 bilayer under different stabilities of the PbZrO3 layer. In addition, we explore cases where the coercive field of the bilayer structure is lower than that of the PbZrTiO3 individual layer. The recoverable electric energy for the PbZrO3/PbZr(0.21)Ti(0.79)O3 bilayer increases significantly to 118 J/cm3 at an applied field of 7.5 × 108 V/m at 20 °C. In comparison, the PbZr(0.21)Ti(0.79)O3 layer reaches 71.8 J/cm3 under the same field and temperature conditions. This is much higher than those predicted experimentally by previous studies on thin film single and bilayer structures (15.6 and 28.2 J/Cm3 respectively), indicating that the antiferroelectric/ferroelectric PbZrO3/PbZr(0.21)Ti(0.79)O3 bilayer bulk structure could be used to target specific large-scale, long-term energy storage applications. Upon increasing the value of the coupling coefficient, the transition temperatures of the PbZrO3 layer and the PbZrO3/PbZr(0.21)Ti(0.79)O3 bilayer are increased up to the transition temperature of the PbZr(0.21)Ti(0.79)O3 individual layer (450 °C). This increment in the transition temperature in the bilayer system contributes to its stability in storing energy at higher temperatures. Furthermore, the recoverable energy density of the PbZrO3/PbZr(0.21)Ti(0.79)O3 bilayer increases further with temperature from 20 to 440 °C correlated with the rise in the difference between the spontaneous and the remanent polarizations (Ps − Pr). The significant stored energy observed over a wide temperature range highlights the promise of this bilayer structure for creating high-power capacitors where stability at different temperatures is crucial and possesses greater energy storage capacity.