Trilayer Films Research Articles

Annealing effect of sputter-grown Pt/Ni80Fe20/Pt sandwich trilayer films on Gilbert damping

The annealing effect of Pt/Permalloy(Py: Ni80Fe20)/Pt sandwich trilayer films on Gilbert damping was investigated through ferromagnetic resonance, x-ray diffraction (XRD), and transmission electron microscopy (TEM) measurements. We estimated the variation of the effective Gilbert damping constant with 30-min-post-annealing temperature in the range of Ta = 600–800 K. The damping constant for the as-grown sample was estimated to be αeff = 0.021, but it linearly increased with Ta until 700 K and then drastically increased by 4.5 times up to αeff = 0.093 at Ta = 800 K. Delicate analyses of the XRD and TEM data revealed that the damping constant in such a thin-layered structure is closely related to the structural characteristics of the interfaces and atomic intermixing through them. The linear increase in αeff in the range of Ta = 650–700 K was ascribed to the alloying/intermixing effect between the Pt and Py layers through both interfaces, whose effect was found to be related to the degradation of the Pt (111) texture. Meanwhile, in the range of Ta = 750–800 K, αeff further and rapidly increased relative to the values in the range of Ta = 650–700 K. Specifically, the 800-K-post-annealed sample showed that its damping constant was 4.5 times larger than that of the as-grown sample, its saturation magnetization decreased by ∼54%, and also that new stoichiometric compounds such as NiPt, FePt, and NiFePt appeared. TEM equipped with energy-dispersive x-ray spectroscopy also revealed that Ta gives rise to atomic intermixing between the Pt and Py thin layers through both interfaces, resulting in interface shifting. This work provides the means to control the Gilbert damping constant and better to understand complex multi-layered structures in potential spintronic devices.

Merged-Element Transmon

Transmon qubits are ubiquitous in the pursuit of quantum computing using superconducting circuits. However, they have some drawbacks that still need to be addressed. Most importantly, the scalability of transmons is limited by the large device footprint needed to reduce the participation of the lossy capacitive parts of the circuit. In this work, we investigate and evaluate losses in an alternative device geometry, namely, the merged-element transmon (mergemon). To this end, we replace the large external shunt capacitor of a traditional transmon with the intrinsic capacitance of a Josephson junction (JJ) and achieve an approximately 100 times reduction in qubit dimensions. We report the implementation of the mergemon using a sputtered Nb--amorphous-Si--Nb trilayer film. In an experiment below 10 mK, the frequency of the readout resonator, capacitively coupled to the mergemon, exhibits a qubit-state dependent shift in the low power regime. The device also demonstrates the single- and multi-photon transitions that represent a weakly anharmonic system in the two-tone spectroscopy. The transition spectra are explained well with master-equation simulations. A participation ratio analysis identifies the dielectric loss of the a-Si tunnel barrier and its interfaces as the dominant source for qubit relaxation. We expect the mergemon to achieve high coherence in relatively small device dimensions when implemented using a low-loss, epitaxially-grown, and lattice-matched trilayer.

Ultrahigh energy storage density at low operating field strength achieved in multicomponent polymer dielectrics with hierarchical structure

Dielectric composites with excellent capacitive energy storage capabilities have great potential applications in energy storage capacitors operating efficiently at relatively low field strengths. Herein, unlike the traditional methods via the introduction of fillers including randomly distributed ceramic nanofibers and aligned nanowires arrays into the monolayer films are simply to increase the energy storage density (Ue), both Ue and charge–discharge efficiency (η) at low electric field strengths have been improved in tri-layered all-polymer films owing to the synergistic effect of multiple interbedded interfaces and deliberately modulation of linear dielectric poly(methyl methacrylate) (PMMA) contents. The effects of film structure on the energy storage capabilities have been comparatively discussed. Consequently, an ultrahigh Ue of 15 J cm−3 accompanied with great η of 76.5% has been delivered in the resulting tri-layered film via optimizing the PMMA content (30 wt%) of out layers at 350 MV m−1, surpassing the energy storage upper limits of the reported polymer dielectrics that show the Ue of ~12 J cm−3 and η of ~70% at comparable electric fields of 310–380 MV m−1. Along with high pulsed power density, multicomponent polymer dielectrics with hierarchically structure provide an effective paradigm for achieving the low operating field strength applications of capacitive energy storage devices with excellent energy storage capability.

Effect of Graphene Thin Layer on a Static and Dynamic Magnetostrictive Behavior in TbDyFe Multi-Layered Film for Micro Energy Devices.

Magnetos-mechanical behaviors of TbDyFe/Graphene/TbDyFe film were compared with a tri-layered TbDyFe film to verify the effects of a graphene thin layer on the improvement of magnetic-mechanical performance, as well as decrease of dynamic response time under the low magnetic field. Both of the Heisenberg model and Landau-Lifshitz-Gilbert equation were used to calculate the magnetic domain motion. Time consumptions were simulated to determine a uniformly magnetized state in Graphene and TbDyFe layers. To ensure the magnetostrictive characteristics, the magnetic moment and the magnetostriction were measured using a fabricated magnetostrictive actuator. Compare to the three-layer TbDyFe films, TbDyFe/Graphene/TbDyFe showed a higher magnetostrictive behavior in response to low coercive forces in the range of 0 to 10 kA/m, even with the addition of low magnetic fields. The dynamic magnetostriction response time was faster than the tri-layered TbDyFe film by approximately 24 millisecond.

Fabrication and thermo stability of the SnO2/Ag/SnO2 tri-layer transparent conductor deposited by magnetic sputtering

Using the magnetic sputtering technique, the SnO2/Ag/SnO2 tri-layer transparent films were fabricated on float glasses successfully. Compared with the commercial FTO (F-doped SnO2) film, the SnO2/Ag/SnO2 tri-layer films have higher visible-light transmittance and better conductivity. The total thickness of the SnO2/Ag/SnO2 films is one third of the commercial FTO film leading to the high visible-light transmittance. The high carrier concentration of the SnO2/Ag/SnO2 films contributes to the tri-layer films’ low resistivity. In addition, to further improve the performance of the SnO2/Ag/SnO2 tri-layer films, samples were annealed under different temperatures. The results illustrate that the lowest sheet resistance (5.92 Ω/sq) and the highest visible-light transmittance (87.0%) were obtained after annealing at 200 °C. Furthermore, the thermal stability of the films could be enhanced by a multi-step annealing process due to the recrystallization effect.

Nonmagnetic Layer Thickness Dependence of Exchange Bias and Coercive Fields in NiFe/NM/FeMn (NM = Cu, Ru) Trilayers with Long-Range Exchange Bias Effect

Trilayer films consisting of ferromagnetic NiFe, nonmagnetic Cu or Ru, and antiferromagnetic FeMn layers were prepared by sputtering technique. The long-range exchange bias properties were investig...

Investigation of ultra-thin and flexible Au–Ag–Au transparent conducting electrode

The performance of ultra-thin Au–Ag–Au tri-layer film deposited thermally over a flexible substrate is investigated using structural, optical, mechanical and electrical-transport measurements. The optimum total thickness of the tri-layer for high transparency and conductivity is determined to be around 8 nm using a theoretical model. The Au–Ag–Au tri-layer shows maximum transmittance (≅ 62%) at wavelength 500 nm. XRD pattern shows peak corresponding to (111) plane of Au and/or Ag. Sheet resistance (≅ 10.42 Ω/□) measured at 300 K using four probe technique is stable up to 150 °C. Hall effect measurements show high conductivity (1.34 × 105 (Ω cm)−1), carrier concentration (2.48 × 1023/cm3), and mobility (3.4 cm2/Vs). Scotch tape test confirms good adhesion of the film onto PET substrate. Bending-twisting tests using an indigenous apparatus indicate high resistance-stability even after 50,000 cycles. These results imply the viability of Au–Ag–Au tri-layer film as a transparent conducting electrode worth exploring for optoelectronic applications.

The thickness of buffer layer and temperature dependent magneto dynamic properties of Ta/FeGaB/Ta tri-layer

In this paper, we have deposited a tri-layer film stack of Ta (25, 50, 75 and 100 nm)/FeGaB (100 nm)/Ta (5 nm) onto Si substrates, and studied ferromagnetic resonance (FMR) properties of the Ta buffer layer thickness and temperature dependence. The surface morphology of the tri-layer film stack is captured by Atomic Force Microscopy (AFM). The static magnetic properties for different buffer layer thickness reveal that both coercive field and remanent magnetization decrease for increasing the Ta buffer layer thickness due to the disturbance of magnetic moments from the FeGaB layer. The dynamic ferromagnetic properties of all samples suggest that narrow inhomogeneous linewidth and low damping factor are obtained for different Ta buffer layer thickness. Ta (100)/FeGaB (100)/Ta (5) film stack shows the lowest damping from 100 K to 300 K. The buffer layer thickness and temperature dependence studies indicate that the interface damping dominates at low temperature 100 K. Hence, these studies are of great importance for development of magnetostrictive microwave devices applications.

Improved biaxial texture of tri-layer YBCO/CaTiO3/YBCO films using an all chemical solution deposition method

The chemical solution deposition (CSD) is one of the most appealing routes for the growth of high-quality YBa2Cu3O7-δ (YBCO) films due to its advantages of low cost and high efficiency. However, as with other preparation methods such as pulsed laser deposition (PLD), the critical current densities (JC) of YBCO films prepared by the CSD method also dramatically decrease with increasing film thickness, which is known as thickness effect. In this paper, the tri-layer YBCO/CTO/YBCO thick films were deposited on buffered Hastelloy C276 tapes by using a dip coater based on all CSD method. By means of the introduction of the CTO interlayer, the JC reduction with increasing film thickness was inhibited, arising from the improvement of the biaxial texture in the tri-layer thick film. The JC value (77 K, self-field) of the tri-layer film was around 3.3 MA/cm2. The texture improvement was mainly ascribed to the interface levelling through the deposition of the CTO interlayer which is a template with good biaxial texture for the epitaxial growth of YBCO film.

Trilayer Films of YBa2Cu3O7−x/LaAlO3/YBa2Cu3O7−x with Superconducting Properties Prepared via Sol-Gel Method

The YBa2Cu3O7−x/LaAlO3/YBa2Cu3O7−x (YBCO/LAO/YBCO) heterogeneous trilayer film structures were prepared on the LaAlO3 (001) single-crystal substrate via the sol-gel method. The characteristics of the phase, orientation, and superconducting properties were studied via an X-ray diffractometer and a comprehensive physical property measurement system. The results show that when the LAO layer was thin (<40 nm), the trilayer films were relatively pure and had a high c-axis orientation. When the nominal thickness of the LAO layer increased to 70 nm, non-c-axis oriented grains started to appear in the trilayer film. In this case, the top and bottom YBCO layers exhibited superconducting properties, and the resistance was found to be zero at 80.1 and 72.5 K, respectively. In addition, for the YBCO/LAO (40 nm)/YBCO structure, the intermediate LAO layer was too thin to completely cover the surface of the underlying YBCO. This resulted in point contact and micro-bridge contact in several micro-regions, thus forming a weak connection and exhibiting a current-voltage (I–V) characteristic similar to the direct-current (DC) Josephson effect. On the other hand, for the YBCO/LAO (70 nm)/YBCO structure, the thicker LAO layer could completely cover the underlying YBCO surface, which could isolate the superconducting current between the YBCO layers.

Sol-gel derived ITO-based bi-layer and tri-layer thin film coatings for organic solar cells applications

In this investigation, ITO-based bi-layer and tri-layer thin film coatings (~130 nm) were synthesized via a sol-gel spin-coating process and annealed at 500 °C. Thin layers of Au, Au-NPs, Ag-NPs and AgO were inserted underneath ITO films to form bi-layer thin film systems and/or encapsulated between two thin ITO layers to form tri-layer thin film systems. The effects of incorporating these layers with ITO thin films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), UV–Vis spectroscopy, four-point probes and Hall effect. XRD results confirmed the presence of a body-centred cubic structure of indium oxide for all synthesized ITO-based coatings with an average grain size ~30 nm. FESEM images of all fabricated films revealed the formation of dense surfaces with grain-like morphologies confirming the formation of a polycrystalline structure of ITO. Optical studies on the Ag-NPs and Au-NPs colloidal solutions resulted in absorption peaks featured at wavelengths 405 and 531 nm, indicating the formation of 10–14 nm and 48 nm Ag and Au nanoparticles, respectively. The highest optical transparency and band gap energy were found to be ~91.5% and 3.75 eV for (AgO)I and (I(AgO)I) thin films, respectively. The lowest electrical resistivity of 1.2 × 10−4 Ω·cm, along with the highest carrier concentration of 11.4 × 1020 cm−3 and mobility 40 cm2/V.s were obtained from the IAuI thin film. An improvement in the power conversion efficiency (PCE) from 3.8 to 4.9% was achieved in an organic solar cell by replacing the conventional pure ITO electrode with the (I(AgO)I) electrode.

Enhanced superconducting properties and microstructures of Y0.5Gd0.5B2C3O7-δ/ LaGdZr2O7/ Y0.5Gd0.5Ba2Cu3O7-δfilm

Thickness effect severely limits the performance of REBa2Cu3O7-δ coated conductors. In this work, a Y0.5Gd0.5B2C3O7-δ/LaGdZr2O7/Y0.5Gd0.5Ba2Cu3O7-δ (YGdBCO/LGZO/YGdBCO) tri-layer film was fabricated by pulse laser deposition, which successfully inhibited the thickness effect and improved the superconductivity of YGdBCO film. By investigating the microstructure of the inserted LGZO layer, it was found that LGZO interlayer can not only reduce the surface roughness of the bottom YGdBCO layer by inhibiting the continuous growth of YGdBCO crystal grains but also realize the transmission of current between superconducting layers. With the deposition of LGZO interlayer, the critical current of the YGdBCO film increased significantly by nearly 50% from 180 A of a double-layer YGdBCO film with the same thickness to 270 A. Transmission Electron Microscope (TEM) observation and Energy Dispersive Spectroscopy (EDS) analysis indicate that the incomplete oxidized particles in the LGZO layer serve as the current channels between YGdBCO layers in the samples prepared at a laser energy of more than 210 mJ.

Highly improved responsivity of self-powered UV–Visible photodetector based on TiO2/Ag/TiO2 multilayer deposited by GLAD technique: Effects of oriented columns and nano-sculptured surface

The outstanding progress made in optoelectronic technologies calls for a renewed performance assessment of photodetectors (PDs) for next-generation sensing applications. Here, TiO2/Ag/TiO2 tri-layered films were sputtered using the GLancing Angle Deposition (GLAD) technique in which the deposition angle was varied from 0 to 80°. Before the elaboration, a strategic combination of Genetic Algorithm (GA) and numerical analysis was used to find out the best multilayer geometry offering superior optical performance. The influence of the inclined architecture on the performance of the prepared TiO2/Ag/TiO2 multilayer was analyzed. Optical characterization reveals that near-perfect UV photodetection and over than 60% of visible-absorbance were achieved by taking a deposition angle of 80°. These enhancements are correlated to the surface nano-sculptured structures, which gives rise to an enhanced light-trapping capability. The measured I-V curves of the obliquely-deposited structures showed a clear photovoltaic mode and an extremely low dark current of a few picoamperes. Besides, the devices demonstrate an enhanced self-powered UV–Vis photoresponse, yielding superb UV and visible responsivity of 0.2A/W and 47 mA/W, respectively. The UV, blue, and green current ratios were respectively 137, 113, and 107 dB. Therefore, promoting efficient light management, this innovative concept of inclined tri-layer films provides a sound pathway for designing potential alternative self-powered UV–Vis PDs appropriate for the future development of the optoelectronic technology.

Tuning the optical properties of SnO2/Ag/SnO2 tri-layers by changing Ag thickness

In this work, for the first time, the effect of changing Ag thickness on the optical and electrical properties of SnO2/Ag/SnO2 tri-layered films prepared by magnetron sputtering equipped with glancing angle deposition has been investigated. Several parameters such as figure of merit (FOM), sheet resistance, NIR emissivity, and refractive index have been studied for the structure prepared by the different thickness of Ag. It has been found that the sample with thickness of 100 and 25 nm, respectively, for the SnO2 and the Ag layers has the maximum FOM of 44.37 × 10−4 Ω−1, the sheet resistance of 7.53 Ω/sq, average transmittance of 71.18% and NIR emissivity of 0.093 which shows the remarkable impact of the glancing angle deposition technique on the optical and electrical parameters of these structures.

Robust resistive switching performance of pulsed laser deposited SiC/Ag/SiC tri-layer thin films deposited on a glass substrate

In this work, the authors developed SiC(10 nm)/Ag/SiC(10 nm) thin films showing an electroforming-free resistive switching (RS) effect with a switching ratio of 102. The observed RS effect is attributed to charging and discharging of Ag nanoparticles in the film layer. Further, SiC/Ag/ SiC film shows an excellent endurance and retention as well as a good thermal stability of RS characteristics. It is also identified that the switching ratio is invariant but the switching voltage of the device greatly depends on the Ag nanoparticles concentration and the operation temperature of the device. Therefore, SiC/Ag/SiC thin films are attractive for next-generation memory devices with enhanced durability.

Nanocrystalline polymorphic oxide perovskite-based high-κ low-leakage thin film materials

We report on thin-film nanocrystalline polymorphic BaTiO3 for enabling high dielectric and low leakage response. BaTiO3-Al2O3 bi-layer thin films based on nanocrystalline BaTiO3 containing the tetragonal and hexagonal polymorphs were deposited by atomic layer deposition. Polymorphic BaTiO3 film combined with a ≈ 3.5-nm thick Al2O3 layer located between the BaTiO3 film and top electrode exhibits dielectric constant of 108 or 130 and leakage currents 2.2 × 10−8 A/mm2 or 1.3 × 10−7 A/mm2 at 1 MV/cm, respectively. Where x-ray photoemission analysis of barrier heights for the metal-BaTiO3-Al2O3-metal structure point to using the polymorphic BaTiO3 interspersed between Al2O3 layers in tri-layered dielectric thin film capacitors, the outstanding combination of high dielectric constant and low leakage current for the polymorphic BaTiO3 - Al2O3 thin film stacks is superior to common high-κ polycrystalline thin film materials.

Effect of structural design on the electrical, optical and mechanical properties of flexible BaSnO3–Ag composite thin films

Barium stannate (BaSnO3, BS) and silver composite thin films are deposited on flexible polyethylene terephthalate (PET) substrates by magnetron sputtering. The effects of structural design on electrical and optical properties of the BS/Ag/BS tri-layer flexible thin films are investigated systematically. The BS layers can enhance the transmittance significantly, due to the fact that reflection of light from the Ag layer and PET substrate can be suppressed by BS layers. The tri-layer thin films show the high figure of merit of 16.66 × 10−3 Ω−1 and the large commutation quality factor of 197, while the average optical transmittance in the visible light range is above 84% and the sheet resistance is 10.52 Ω/sq. In addition, the flexible tri-layer thin films show outstanding mechanical flexibility, adhesion to PET substrate and stability at high temperature.

Characterization and antioxidant activity of trilayer gelatin/dextran-propyl gallate/gelatin films: Electrospinning versus solvent casting

In this study, trilayer films were prepared with an electrospun dextran interlayer, and gelatin outlayers fabricated by solvent casting and electrospinning, respectively. The trilayer film either with casted or electrospun outlayers showed an enhanced thermal stability, and acceptable color and opacity properties. Compared to the electrospun outlayers, the casted outlayers endowed the trilayer film with improved oxygen and water vapor barrier properties, and significantly enhanced the elastic modulus and tensile strength, indicating a greater resistance to deformation. The DPPH radical-scavenging activity assay indicated that the applied electrospun or casted outlayers effectively prolonged the release time of propyl gallate from the interlayer by 2-fold or more, with a sustained antioxidant activity. These results suggest the promising applications of multilayer films as active packaging materials with prolonged release of antioxidants to retard oil oxidation in the food industry.

Unconventional superconducting phases in multilayer films with layer-dependent Rashba spin-orbit interactions

We present resistivity measurements of bilayer and trilayer films with layer-dependent Rashba spin-orbit interactions. A sharp upturn is observed in the temperature dependence of the parallel upper critical field. We show that it corresponds to a transition from a complex-stripe phase to a helical phase. Moreover, we propose the phase diagram of a multilayer system, which is obtained from experimental observations with the support of numerical calculations. These results pave the way for the clarification of non-trivial superconducting states in multilayer systems composed of two-dimensional Rashba superconductors.

The investigation of ZnS/Au/ZnS transparent conductive films with different Au layer thickness

ZnS/Au/ZnS (ZAZ) transparent conductive tri-layer films with different Au layer thickness have been prepared by a pulsed laser deposition technique, and the effect of Au layer thickness on the optical and electrical properties of ZAZ films has been studied in detail. As-deposited ZAZ films showed an intense X-ray diffraction peak corresponding to ZnS (111) orientation and a very weak peak belonging to the Au (111) plane. The optical transmittance first increases and then decreases with the increase of Au layer thickness, which is due to the fact that Au changes from discontinuous island-shape to near-continuous structure when Au increases from 2 to 10 nm, and when Au is above 10 nm, the reflection of Au layer is enhanced. With the increase of Au layer thickness, both the sheet resistance and the resistivity of ZAZ films decrease, and the carrier concentration and the mobility increase. When the Au layer thickness is 10 nm, ZAZ films have the best figure of merit of 2.44 × 10−3 Ω−1.