Oxide Multilayer Films Research Articles

Wideband optically transparent absorber based on multilayer ITO films with high absorption rate.

In this paper, a wideband optically transparent absorber based on multilayer indium tin oxide (ITO) films is designed, fabricated, and measured. The structure uses polyethylene terephthalate (PET) and ITO films to replace the dielectric substrate and metal pattern of the traditional absorber to achieve optical transparency characteristics. The absorption of the proposed absorber is above 90% from 4.92 to 24.55 GHz and exceeding 95% in the range of 5.74 ∼ 21.85 GHz, respectively, under normal transverse electric (TE) and transverse magnetic (TM) polarized incidences. Moreover, it shows outstanding stability with various incident angles over a wide range. A prototype of the proposed absorber is fabricated and experimentally verified, with good measurement results. The optical transparency and great absorption performance make the absorber a promising candidate for transparent electromagnetic compatibility.

Numerical study of mid-infrared broadband perfect absorber based on dielectric/aluminium doped zinc oxide multilayer films

We propose a lithography-free wide-angle polarization-insensitive ultra-broadband absorber by using multilayer films consist of five pairs of aluminium doped zinc oxide (AZO) and a dielectric film which is supposed to be fabricated on glass substrate. The absorption spectrum of the proposed model is calculated by using transfer matrix method. The analytic results show that the absorptivity is larger than 95% with normal incidence light in the wavelength range from 7.5μm to 20μm and having high transmittance at the visible wavelength range from 0.4μm to 0.8μm range. Further, the effect of incident angle and polarization on the absorption spectrum are also investigated. The absorption spectrum of the proposed design is highly tunable on changing the damping constant of the AZO film. The electric field and magnetic distributions at different wavelengths show that the absorption is mainly originated due to the constructive interference of electromagnetic waves in the multilayer films. Such physical mechanism of broadening bandwidth based on increasing the carrier concentration of the highly visible transparent conducting films have pave a new direction for the design of tunable broadband absorber in different frequency band. Meanwhile, this broadband absorber is a good candidate for the potential applications in daytime radiation cooling system in the mid-infrared frequency band and also used as transparent conducting electrode in solar cell applications.

On oxidation film structure of SIMP steel exposed in stagnant oxygen-saturated LBE at 600 °C

To understand the impact of multilayered oxide films on the liquid-metal resistance, SIMP steels with three different Si levels were investigated. A novel composite oxidation film, namely amorphous SiO2 packed by Cr2O3, was formed along the prior high-angle grain boundaries in internal oxidation zone to impede the inward diffusion of oxygen. Evolved into the inner layer, the amorphous SiO2 films stayed there, while Cr2O3 transformed into FeCr2O4. Moreover, outward diffusion of chromium facilitated the transformation from lower sublayer to upper sublayer in inner layer. This multilayer plays a critical role in improving the oxidation resistance of SIMP steel.

Understanding the role of oxide layers on color generation and surface characteristics in nanosecond laser color marking of stainless steel

This study conducts an experimental analysis of Laser Color Marking (LCM) on Stainless Steel, aiming to elucidate the role of oxides in color formation. Employing a nanosecond pulsed fiber laser, we systematically varied process parameters to successfully generate a diverse array of distinctive colors. Remarkably, a myriad of colors became evident at the micro-scale, offering a striking contrast to the macroscopic view dominated by a singular prominent color. These colors exhibited a notable increase in oxygen composition, reaching levels as high as 24.5%, coupled with the formation of a thin oxide film spanning thicknesses from 220 to 850 nm. The prevalence of chromium oxides resulted in greenish or bluish shades, whereas iron oxides’ dominance produced brownish and reddish hues. Particularly intriguing was the revelation of a multi-layer oxide film in samples like brown. Furthermore, the nature of oxides was also found to have an influence on surface characteristics. Chromium oxide-dominated colors exhibited ablation depth, while iron oxide-dominated colors resulted in surface overgrowth due to their porous nature. Correspondingly, Vickers hardness of samples dominated by chromium oxides showcased a significant enhancement in microhardness compared to those with iron oxide dominance. Lastly, we observed minimal degradation in surface roughness characteristics after LCM, with variations ranging from 262 nm to 463 nm, compared to 150 nm for untreated samples. These comprehensive findings provide valuable insights for optimizing the LCM process for stainless-steel color markings.

Enhanced electrodynamic characteristic and tunable band gap formed by the multilayer TixZn oxide film promising as a photoanode for solar cells

As a clean and efficient energy material, the efficiency of solar battery can be greatly promoted by matching suitable photoanode. Among them, TiO2 and ZnO are natural materials with appropriate energy level and excellent carrier concentration, which have enormous application potential. Herein, a multilayer Ti10Zn oxide film with similar band gap of TiO2 (ECB=−0.70 V vs. NHE) and a parallel electrical property of ZnO has been obtained by atomic layer deposition (ALD). The formation mechanism has been analyzed by comparing multilayer TixZn oxide films with different proportions and pure TiO2 (ZnO) film. Firstly, scanning electron microscope (SEM) indicating homogeneous morphology of these films. Then X-ray photoelectron spectroscopy (XPS) along with the X-ray diffraction (XRD) measurements and the thicknesses fitted by ellipsometric spectra reveal that when x > 10, the ZnO substance mainly exist in the form of interstitial atoms and conversely occupies a separate layer of spatial structure when x < 10. While the film shows maximum Zn 2p3/2 binding energy and preferential growth orientation of spacing in (002) direction with ZnO-like crystal structure when x = 10 (Ti10Zn). The resistivity and Hall measurement confirm Ti10Zn with an excellent electrodynamic property with a parallel Hall mobility of 9.34 cm2 and carrier density of 1.86 × 1020 cm−3 even higher than that of pure ZnO. Transmission spectra along with photo-luminescence measurement demonstrated similar band gap values of TixZn oxide films with TiO2 and high spectral transmittance (solar light utilization rate>70%). This work highlights TiO2/ZnO composite films with great application prospects as solar cell photoanode materials and other optoelectronic application fields.

Tuning Ionic Conductivity in Fluorite Gd-Doped CeO2-Bixbyite RE2O3 (RE = Y and Sm) Multilayer Thin Films by Controlling Interfacial Strain.

Interfacial strain in heteroepitaxial oxide thin films is a powerful tool for discovering properties and recognizing the potential of materials performance. Particularly, facilitating ion conduction by interfacial strain in oxide multilayer thin films has always been seen to be a highly promising route to this goal. However, the effect of interfacial strain on ion transport properties is still controversial due to the difficulty in deconvoluting the strain contribution from other interfacial phenomena, such as space charge effects. Here, we show that interfacial strain can effectively tune the ionic conductivity by successfully growing multilayer thin films composed of an ionic conductor Gd-doped CeO2 (GDC) and an insulator RE2O3 (RE = Y and Sm). In contrast to compressively strained GDC-Y2O3 multilayer films, tensile strained GDC-Sm2O3 multilayer films demonstrate the enhanced ionic conductivity of GDC, which is attributed to the increased concentration of oxygen vacancies. In addition, we demonstrate that increasing the number of interfaces has no impact on the further enhancement of the ionic conductivity in GDC-Sm2O3 multilayer films. Our findings demonstrate the unambiguous role of interfacial strain on ion conduction of oxides and provide insights into the rational design of fast ion conductors through interface engineering.

High-quality, binder-free, homogeneous, robust and multilayer functional graphene oxide films on copper by electrophoresis

High-quality, binder-free, homogeneous, robust and multilayer functional graphene oxide films on copper by electrophoresis

Energetics and diffusion kinetics of point defects in MnCr2O4 spinel from first principles

MnCr2O4 spinel is a component of the multilayered oxide film which forms atop austenitic steel alloys under high-temperature corrosion conditions. In this work, the thermodynamics and kinetics of cationic and anionic point defects in this spinel are examined through density functional theory calculations. To model the physical conditions of the corrosion process more closely, temperature is accounted for by adjusting the chemical potential of each species to fit experimentally determined values. We find that manganese is the most mobile species - migrating through the lattice via a vacancy mediated mechanism. Oxygen migration can occur via vacancy mediated or three-body interstitial mechanisms with similarly low barrier heights, highlighting the possibility of oxide growth at the film/alloy interface due to the high oxygen permeability. Furthermore, a number of more complex migration mechanisms involving substitution and antisite defects are evaluated for their potential contribution to cation mobility.

Effect of laser remelting on high-temperature oxidation resistance of AlCoCrFeNi high-entropy alloy coating

To reveal the effect of laser remelting on the high-temperature oxidation resistance of high-entropy alloy (HEA) coating, an AlCoCrFeNi HEA coating was prepared on AISI 1045 steel by plasma spraying technology and then remelted by laser remelting process. The microstructure of the coatings before and after remelting was characterized, and oxidation experiment was carried out at 900 °C for 100 h. The results showed that, after laser remelting, the porosity of AlCoCrFeNi HEA coating decreased from 4.8 % to 0.3 %. Moreover, the phase compositions of the coating after remelting were the same as that before remelting, which were still dominated by a single BCC solid solution structure. After oxidation, the oxidation weight gain of the remelted coating was slightly greater than that of the as-sprayed coating. Nevertheless, uniform and dense multilayer oxide films were formed on the remelted coating surface, leading to the lower oxygen content in the remelted coating and at the interface of remelted coating/substrate. Therefore, laser remelting can effectively improve the ability of AlCoCrFeNi HEA coating to hinder oxygen at high temperature and prevent the substrate from oxidation.

The Formation Mechanism of a Multilayer-Structure Oxide Film during the Oxidation of FeCrAl in Air at 700 °C

A protective oxide film is the key to the corrosion resistance of the FeCrAl alloy. The mechanism of the formation of the multilayer oxide film of the FeCrAl alloy in 700 °C air was explored by studying the structure evolution of the oxide film and the oxidation kinetics of FeCrAl. The results show that a multilayer oxide layer is formed on the surface of the FeCrAl alloy after 1344 h, with a (Fe,Cr)2O3 layer, an Al-rich oxide layer, an Al-depleted zone, and a new Al-rich oxide layer sequentially arranged from the surface to the matrix. This indicates that the Al element plays an important role in the formation of the oxide film. The Al in the matrix is depleted to form the Al-rich oxide layer, resulting in the Al-depleted zone. The new Al-rich oxide layer is formed under the Al-depleted zone by internal oxidation. It should be noted that the precipitation of the AlN phase in the matrix is observed, which might be a probable factor for the Al-depleted zone in the matrix.

ZnO Multilayer Thin Films as The Seed Layer for ZnO Nanorods: Morphology, Structural and Optical properties

The effect of zinc oxide (ZnO) multilayer thin film thicknesses, deposited via the sol-gel spin coating technique, on the morphology, structural and optical properties of ZnO nanorods (ZNR) grown on the ZnO thin films were explored in this investigation. The ZNR was grown using the chemical bath deposition method on the ZnO thin film seed layer (SL). We found that ZnO thin film SL morphology changes according to the number of layers based on the results. Eventually, these changes also influence the structures of ZNR. ZNR structures improved when the thickness of the seed layer increased. Besides the surface roughness, better crystalline quality films were obtained when more layers were deposited. This crystalline quality then influenced the optical characteristics of both ZnO and ZNR thin films. The optical properties from UV-Vis showed transmittance in the visible region, showing that the ZnO films produced were suitable to be applied to solar cells. ZNR-based solar cells have become one of the promising materials to be studied further due to the environment-friendly, low-cost, and well-abundant material for solar cell applications.

In Vitro and Electrochemical Characterization of Laser-Cladded Ti-Nb-Ta Alloy for Biomedical Applications

Titanium (Ti) and its alloys are predominant choices for use as biomaterials in human implants. Research has shown the adverse effects of using commercial Ti alloy Ti-6Al-4V in the human body, and this presents a need for viable alternatives. In this study, Ti alloy Ti-17Nb-6Ta was manufactured by laser cladding—a prominent additive manufacturing (AM) technology. Laser cladded specimens were evaluated for their in vitro and electrochemical behavior. A human osteosarcoma cell line (MG-63 cells) was used for in vitro investigations. Cell proliferation was good in the physiological medium, and cells were alive when in contact with the laser cladded alloy, even after two to three weeks, indicating good cell viability and compatibility with this alloy. Electrochemical characterization was carried out in Ringer’s solution, and noticeably lower corrosion current density and corrosion rate values were observed. The lower amounts of these parameters indicated the passivation behavior due to multi-layer Ti, Nb, and Ta alloy oxide films. These oxide films also enhanced osseointegration. Thus, the Ti-17Nb-6Ta alloy can be an ideal biocompatible alternative to Ti-6Al-4V.

Multi-Layered Sol–Gel Spin-Coated CuO Nanofilm Characteristic Enhancement by Sn Doping Concentration

CuO films, with their many features, attract special attention for applications in various optoelectronics. In their pristine form, CuO films suffer from low conductivity, which limits their application. Modification, especially by doping, is thus needed. The effects of tin (Sn) doping on the structure, morphology, and optical and, more importantly, electrical properties of multi-layered copper oxide (CuO) films deposited onto tin-doped indium oxide (ITO)/glass substrates by sol–gel spin coating are examined here. The multi-layered films were characterized with X-ray diffraction (XRD), atomic force microscopy (AFM), electronic absorption (UV-Visible) spectra, and four probe methods. The results confirmed the substitution of Cu2+ ions by Sn4+ ions in the CuO crystallites without altering their monoclinic structure. The measured crystallite size values decreased with increased doping concentration, indicating increased imperfection. This applies to both 5- and 10-layered CuO films. The doping concentration affected other film characteristics, namely, surface morphology and electrical conductivity, in each layered film. Among various systems, the 10-layered film, with 1.5 at% Sn, exhibited optimal properties in terms of higher uniformity (mean square root surface roughness 41 nm) and higher conductivity (50.3 × 10−3·Ω−1·cm−1).

Fabrication of multilayer film with graphene oxide of different surface charge through electrospray deposition

Due to its notable mechanical and electrical properties, graphene has high-value-added applications in future flexible electronics. The preparation of ultrathin uniform graphene oxide (GO) multilayer film through simple and cost-effective technique still is concern. Herein, we have demonstrated the electrospray deposition (ESD) method to prepare the uniform alternative GO multilayer film with controlled thickness by alternatively depositing the different surface charge. It is a solution-processed technique that can be applied in a variety of practical applications due to low-cost and high-speed processing time. Colloidal nanoparticles, which is deposited through ESD technique, have different physical and optical properties based on surface charge. Owing to the electrostatic repulsion between the functional groups, GO can be well soluble, homogeneous and stable dispersion. The prepared alternated rGO films enhanced the sheet resistance because of improving electrical conductivity. Furthermore, alternated rGO film is utilized in the symmetric supercapacitor and the device exhibit a larger capacitance of 103.5 F/g at 0.5 A/g and good cycling stability (94%) on the account of high conductivity than that of other prepared rGO based films. These attributes of ultra-thin rGO film underscore the potential of the current method towards the understanding of film-based supercapacitors in a numerous energy storage applications.

Effect of inhomogeneous composition on the passive film of AISI 431 coating fabricated by extreme-high-speed laser cladding

The effect of inhomogeneous composition of Cr and Fe on morphology and formation mechanism of passive film was investigated. A bi-layer structure passive film with a Cr2O3 inner layer and a Fe2O3 outer layer obtained on EHLA coating. The passive film is heterogeneous (thickness, compactness) between inter-dendrite and dendrite core due to the element segregation and dislocation. Aspects of the passive film formation mechanism are discussed according to the thermodynamics. It indicates the prior oxidation of chromium resulting in the formation of inner Cr-rich layer, while higher diffusion rate of Fe3+ is the main reason for the formation of outer Fe-rich layer. This provides a new sight on the formation of multilayer oxide films.

Wide Band BAW Filter Based on Single-Crystalline LiNbO₃ Thin Film With Insulating Bragg Reflector.

Bulk acoustic wave (BAW) filter with large bandwidth is an urgent need in fifth-generation (5G) communication systems. In the present work, 43° Y-cut lithium niobate (LN) single-crystal film is prepared on multilayer oxide film, and bulk acoustic filter with oxide Bragg reflector (BR) is successfully achieved. The design method of the filter and the fabrication process are presented. Atomic force microscope (AFM) and scanning electron microscope (SEM) are used to characterize the quality of thin films. The results demonstrate the feasibility of transferring single-crystal film onto multilayer oxide, which is efficient for the confinement of acoustic energy. The resonator has effective electromechanical coupling coefficient of 14.6% and figure of merit (FOM) of 32.94. The filter with a compact size of 600 [Formula: see text] has a relative bandwidth of 10.3% at a center frequency of 3.128 GHz, which is promising for the application of 5G systems.

Multi‐Hierarchical Microstructures Boosted Linearity of Flexible Capacitive Pressure Sensor

Besides the excellent sensitivity, linearity is also highly required for a miniaturization and low power consumption of the flexible sensor system. Herein, multi‐hierarchical microstructures to improve the linearity of capacitive pressure sensor based on poly(vinylidene fluoride)/reduced graphene oxide (PVDF/rGO) multilayer films is designed and constructed. The differentiated hierarchical microstructure in each layer comes from irregular protrusions with various roughness. Excellent sensor performances, such as higher sensitivity (0.18 kPa−1) in the linear range from 0.1 kPa to 11 kPa, lower limit of detection (100 Pa), rapid response time (56.3 ms) compared with some current reports, are obtained in the sensor based on three laminated films with the successive roughness (remarked as 150/400/800 Cw films). Moreover, the device exhibits outstanding stability over 3000 cycles at a pressure of 10 kPa, and successfully works on the falling leaf of 0.16 g and the weight of 100 g as well as high heel pressure. These outstanding properties are attributed to the compressibility of the hierarchical structure and efficient stress distribution between stacked multilayers, which is verified by using the finite‐element analysis (FEA). The work provides a simple and low‐cost route for fabricating high‐performance capacitive sensors with diverse potential applications in wearable electronics.

Intermediate Evaporation Controlled SnO2/Mo Doped BiVO4 photoanode for Enhanced Photoelectrochemical Performance

The design of multilayer oxide films heterojuctions for photoanodes enables the control of charge transport/transfer and optical properties, and thus leads to efficient photoelectrochemical performance. In this research, a SnO2/Mo-doped BiVO4/ based photoanode was fabricated by sequential spin coating method on an FTO substrate followed by thermal treatment. First, bottom SnO2 layers were deposited, and subsequently Mo doped BiVO4 layers were loaded. When Mo doped BiVO4 layers were coated, intermediate evaporation was controlled by varying temperature condition for a formation of uniform crystalline film, allowing an improved charge separation. The synthesized photoanodes were examined by SEM, TEM, XRD, UV-vis as well as electrochemical measurements.

Bulk acoustic wave resonance characteristic modified by reducing the defects in ZnO-based solidly mounted resonators

The c-axis zinc oxide (ZnO) multi-layered films and ZnO-based solidly mounted resonators (SMR) based on high-resistivity silicon substrates have been fabricated by using the combination of sputtering and photolithography with the absence of oxygen and heating. Subsequent annealing procedure was performed to improve the quality of ZnO films and devices. The X-ray diffraction (XRD) measurements reveal that all ZnO films are well crystallized and highly textured, the grain size gradually increases from 18.2 to 20.5 nm with the increasing of annealing temperature (Tann). The X-ray photoelectron spectrometer (XPS) results indicate that the high concentration oxygen defects of as-deposited ZnO films can be reduced through increasing Tann. By comparing the measured electrical properties of the devices before and after various Tann annealing, it was found that the annealing treatment can be used to improve the resonance characteristics, the relative change in return loss (S11) increased from 0 to 0.72 dB and then decreased to 0.07 dB as Tann increases from room temperature to 700 °C. In addition, S11 relative change can also be enhanced from 0.29 to 0.67 by decreasing the effective working area of the devices from 100 × 160 μm2 to 100 × 50 μm2.

Construction of a Self-Assembled Polyelectrolyte/Graphene Oxide Multilayer Film and Its Interaction with Metal Ions.

In this study, a composite multilayer film onto gold was constructed from two charged building blocks, i.e., negatively charged graphene oxide (GO) and a branched polycation (polyethylenimine, PEI) via layer-by-layer (LbL) self-assembly technology, and this process was monitored in situ with quartz crystal microbalance (QCM) under different experimental conditions. This included the differences in frequency (Δf) as well as the changes in dissipation to yield information on the absorbed mass and viscoelastic properties of the formed PEI/GO multilayer films. The experimental conditions were optimized to obtain a high amount of the adsorbed mass of the self-assembled multilayer film. The surface morphology of the PEI/GO multilayer film onto gold was studied with atomic force microscopy (AFM). It was found that the positively charged PEI chains were combined with the oppositely charged GO to form an assembled film on the QCM sensor surface, in a wrapped and curled fashion. Raman and UV-vis spectra also showed that the intensities of the GO-characteristic signals are almost linearly related to the layer number. To explore the films for their use in divalent ion detection, the frequency response of the PEI/GO multilayer-modified QCM sensor to the exposure of aqueous solutions solution of Cu2+, Ca2+, Zn2+, and Sn2+ was further studied using QCM. Based on the Sauerbrey equation and the weight of different ions, the number of metal ions adsorbed per unit area on the surface of QCM sensors was calculated. For metal ion concentrations of 40 ppm, the adsorption capacities per unit area of Cu2+, Zn2+, Sn2+, and Ca2+ were found to be 1.7, 3.2, 0.7, and 4.9 nmol/cm2, respectively. Thus, in terms of the number of adsorbed ions per unit area, the QCM sensor modified by PEI/GO multilayer film shows the largest adsorption capacity of Ca2+. This can be rationalized by the relative hydration energies.