Ag Interlayer Research Articles

Effects of nitrogen/oxygen on the electrical and optical properties and microstructure of triple layer AZO/Ag/AZO thin films

Aluminum-doped zinc oxide (AZO)/Ag/aluminum-doped zinc oxide (AAA) specimens are prepared by varying O2 and N2 flow rates during the AZO deposition to investigate the gas effects on surface morphology, microstructure, conductivity type and optical and electrical properties. The AZO specimens are found to have decreases in grain size and RMS surface roughness (SRq), and an increase in compressive residual stress when the N2 flow rate increases higher than 2.5 sccm. The addition of O2 can contribute a similar tendency to grain size, SRq and residual stress; the grain size and SRq are always comparatively smaller, while the residual stress is higher than that prepared with N2. The grain size and SRq are obtained to be proportional to the AZO thickness, whereas they are inversely proportional to the compressive residual stress of AZO. Specimen D prepared with (N2: 0, O2: 2.5) sccm and having 60-nm AZO thickness possesses the strongest anti-reflection effect of the AAA structure, and therefore impedes the reflection from the Ag interlayer significantly. P-type conductivity is achieved by introducing the N2 into the AZO layers and (N2: 15, O2: 0) sccm is used to achieved the highest carrier concentration (CC) and mobility (Mb), and thus the lowest resistivity (R) of all specimens in this study. Increasing the O2 flow rate leads to decreases in Mb and CC, but can obtain the highest average transmittance ( T ¯ ) as (N2: 0, O2: 2.5) sccm is applied. The O2 flow rate becomes the dominant factor for the electrical and optical properties and microstructure as AZO films are deposited in the N2 and O2 mixed atmosphere. (N2: 15, O2: 0) sccm is used to achieve the highest CC and the lowest R of the oxide/metal/oxide specimens reported in the literatures.

Comparing the performance of transparent, conductive ZnO/Ag/ZnO thin films that have an interlayer coating formed by either DC magnetron sputtering or HiPIMS

Transparent electrodes (TEs) are essential components in many optoelectronic devices. Although indium tin oxide (ITO) has an excellent trade-off between optical transparency and electrical sheet resistance, it still suffers from several drawbacks, including the increasing cost of indium and poor long-term flexibility due to work hardening. This work presents the development of a new class of TEs based on ultrathin ZnO/Ag/ZnO samples in which Ag films with different film thickness are used as the metallic interlayer. XRD, XPS depth profiling, UV–vis-NIR spectrophotometer, Hall effect measurement, and a four-point probe system were used to characterize the properties of the fabricated films. Optimum thicknesses of Ag and ZnO top layer films were determined as those having high optical transmittance and good electrical conductivity. The main objective of this work has been to investigate how the density of the Ag interlayer in ZnO/Ag/ZnO film samples affects their optical and electrical properties. Silver layers prepared using DC magnetron sputtering (DCMS) have different densities to those prepared using high power impulse magnetron sputtering (HiPIMS). The optimum figure of merit at 3.53 × 10−3 Ω−1 was achieved for ZnO (0.6 nm)/Ag (9 nm)/ZnO (20 nm) multilayer films in which the Ag interlayer was fabricated using the HiPIMS method.

Improvement of bi-layered YBCO superconducting films by using Ag and Au interlayers

Chemical solution deposition is a promising technology to fabricate YBCO superconducting thin films due to its low-cost advantage. However, the decreasing of critical current density (Jc) usually occurred in the fabrication of multi-layered YBCO films. In this study, Ag and Au heterogeneous interlayers were fabricated by using sputtering deposition in order to improve the bi-layered YBCO films, and the influence of crystallization temperature from 740 ∘C to 800 ∘C was investigated. It was found that Jc could be enhanced by both interlayers relative to the counterparts without interlayers, and the effect of Ag interlayer was superior to that of Au interlayer. When the crystallization temperature was 800 ∘C, the optimal sample with Ag interlayer had a Jc 3.65 MA/cm2, which was about twice of the Jc of its counterpart. The surface morphologies and cross-sections were observed by using scanning electron microscope, and the content variations of c-axis oriented grains were measured by using Raman spectroscopy, which could help to investigate the influences of interlayers on the microstructure of YBCO films. The possible reasons for the improvement effects of Ag and Au interlayers were discussed based on the experimental results.

Transparent Conductive Electrodes of β-Ga₂O₃/Ag/β-Ga₂O₃ Multilayer for Ultraviolet Emitters.

We investigated the optical and electrical properties of a β-Ga₂O₃/Ag/β-Ga₂O₃ multilayer transparent conductive electrode deposited on an α-Al2O₃ (0001) substrate. For the deposition of a continuous Ag layer, we preliminarily performed anultraviolet-ozone pretreatment of the Ga₂O₃ bottom layer. To obtain a stable β-phase of Ga₂O₃, the β-Ga₂O₃/Ag/β-Ga₂O₃ multilayer was annealed at 700 °C under N₂ atmosphere. The transmittance and sheet resistance of the β-Ga₂O₃/Ag/β-Ga₂O₃ multilayer were critically affected by the surface morphology and thickness of the Ag interlayer. The multilayer with optimized thicknesses (β-Ga₂O₃ top layer: 30 nm; Ag interlayer: 12 nm; β-Ga₂O₃ bottom layer: 60 nm) exhibited a resistance of 8.48 Ωsq-1, an average optical transmittance of 87.16% in the ultraviolet wavelength range from 300 to 350 nm, and a figure of merit of 29.81 × 10-3 Ω-1.

Microstructure and mechanical properties of electron beam welded joints of titanium alloy and Kovar alloy with copper or silver interlayer

The electron beam welding experiments of TC4 titanium alloy and kovar alloy were carried out with Cu or Ag Interlayer. The microstructure and composition of the welded joint were analyzed by optical microscope, scanning electron microscope and x-ray diffraction. The mechanical properties of welded joints were evaluated by microhardness and tensile strength tests. The results show that when Cu is used as the interlayer, there are mainly Cu solid solution and TiFe ,Fe2Ti ,CuTi2 in the joint. The highest hardness of weld is 380HV and the tensile strength is 168 MPa. The joint welded with Ag interlayer exhibit brazing characteristics. The hardness of joint is slightly higher than pure silver, and the tensile strength is 243 MPa.

Effects of Rapid Thermal Annealing on the Structural, Optical, and Electrical Properties of ZnO/Ag/SnO2 Tri-Layer Films

ZnO 50 nm/Ag 10 nm/SnO2 50 nm (ZAS) tri-layer films were deposited on a glass substrate by RF and DC magnetron sputtering and then underwent rapid thermal annealing in a low vacuum of 1×10-3 Torr to investigate the effects of post-deposition annealing on the optical and electrical properties of the films. The peak intensity of the XRD pattern related to the ZnO (002) peak of the annealed films was higher than that of the as-deposited film and the full width at half-maximum of the ZnO (002) diffraction peak of the annealed films was smaller than that of the as-deposited film. Therefore, the crystallinity of ZnO was improved by rapid annealing. However, crystallization of the Ag interlayer and SnO2 surface layer were not significantly affected by the annealing temperature, compared with the ZnO bottom layer. From the observed electrical properties and optical band gap, it was concluded that the blue shift in the optical band gap is related to the carrier density of the films. The band gap increased from 4.19 eV to 4.24 eV, with the carrier density increasing from 7.09 × 1021 cm-3 to 7.77 × 1021 cm-3. However, the film annealed at 450 °C showed a decreased band gap energy of 4.17 eV due to the decreased carrier density of 6.80 × 1021 cm-3. The as-deposited ZAS films showed a sheet resistance of 11.0 Ω/□ and a visible transmittance of 80.8%, whereas the films annealed at 450 °C had a higher visible transmittance of 82.3% and a lower sheet resistance of 6.55 Ω/□. The results indicate that ZAS thin films may be possible substitutes for conventional Sn-doped In2O3 transparent electrodes in various optoelectronic devices. Key words: ZnO/Ag/SnO2, magnetron sputtering, annealing, AFM, XRD

Comparing the structural and magnetic properties of FePt/MgO/Si and FePt/Ag/Si granular nanolayers

The properties of L10-FePt nanoparticles can be improved in the presence of MgO and Ag interlayers in direct sputtering and annealing method, respectively. Such properties are crystal and compound ordering, nanostructure and crystal orientation. In this work, FePt nanoparticles in ferromagnetic L10-fct phase were synthesized using sputtering method on Ag and MgO layers. According to XRD analyses, the impact of the presence of these two kinds of interlayer on crystal structure and its orientation has been investigated. Furthermore, the effect of the presence of 10% Ag on these properties has been studied and their granular layer nanostructures were characterized through the FE-SEM analysis. The results show that the presence of Ag as nanocompound and interlayer is desirable on declining the transition temperature and controlling the size during annealing. The presence of MgO as a sublayer in direct synthesis leads to the formation of 10 nm monosize smaller nanoparticles. According to VSM analysis, MgO and Ag sublayers have increased the magnetic coercivity of the FePt nanoparticles by 3.4 times and 3.7 times, respectively.

Fabrication of copper/stainless steel bimetallic couple, by diffusion bonding using silver and nickel foils as interlayers

The Copper/Silver couple was fabricated via diffusion bonding process with the aid of nickel and silver foils as interlayers. The results indicated the width of reaction layer of interfaces was increased with the temperature enhancement. Meanwhile, the utilization of proper interlayer in addition to suitable assembly, for example in the stainless steel-Ni-Ag-Cu specimen bonded at 750 °C, led to qualified bonding even at lower temperature with the maximum shear strength (158 MPa) through all diffusion bonded joints. Additionally, the maximum and minimum micro-hardness were obtained for stainless steel/interlayer interface and Ag interlayer in each joint, respectively.

Interfacial modification of Li/Garnet electrolyte by a lithiophilic and breathing interlayer

Garnet type electrolyte is of particular interest due to its outstanding stability against Li metal and high ionic conductivity at room temperature. But insufficient solid to solid contact hinders its further application on solid state batteries. Herein, we demonstrate a strategy to deal with the large impedance of Li/Garnet interface by introducing LiAg alloy reaction at the interface. Due to the lithiophilic nature of Ag interlayer, intimate contact of the interface successfully reduces the area specific resistance of Li/Garnet from 1534 Ωcm2 to 66 Ωcm2. Li dendrite is also suppressed not only at the Li/Garnet interface but among the Garnet grain boundary due to the moderate Li flux environment. Hybrid solid state Li/Garnet/LiMn2O4 full cell with remarkable electrochemical properties is achieved. The hybrid solid state batteries with a “breathing” Li/Garnet interface helps better understand the interface behavior of the Li/Garnet and provides more inspirations to further realize solid state batteries with high energy and power density.

RF magnetron-sputtered Al–ZnO/Ag/Al–ZnO (AAA) multilayer electrode for transparent and flexible thin-film heater

We report the electrothermal properties of AAA trilayer on polyethylene terephthalate substrate which allowed the development of low-cost high-performance transparent thin-film flexible heater (TTFFH) using RF magnetron sputtering. The structural, electrical, and optical properties of the AAA trilayer were investigated at different thickness of the Ag interlayer. The AAA trilayer-based TTFFH yielded saturation temperatures beyond 100 °C at 10 V at optimized Ag interlayer thickness of 5 nm. The time-dependent temperature profile along with its highly stable and reversible thermal behavior was studied. Most importantly, the AAA trilayer-based TTFFH provides a high-performance alternative to the conventional and expensive ITO electrodes at a much lower cost.

An investigation on diffusion bonding of Zircaloy-4 and 304L stainless steel with Ti and Ag multiple interlayers

Diffusion bonding of Zircaloy-4 and 304L stainless steel (SS) was carried out using Ti and Ag as multiple interlayers at 800 °C under 12 MPa for 15–120 min. Microstructure and mechanical properties of the joints were investigated. The results showed that the interface zone of the joints consisted of 304L SS substrate, Ag interlayer, α-Ag + TiAg layer, Ti interlayer, Ti(Zr) solid-solution layer, Zr(Ti) solid-solution layer and Zircaloy-4 substrate. The shear strength of the joints increased firstly and then decreased with increasing bonding time, and the maximum shear strength of 165.7 MPa was reached for 90 min. Although there was TiAg IMCs formed in the joints, which did not lead to hardening of the joints. The layer growth for α-Ag + TiAg layer, Ti(Zr) layer and Zr(Ti) layer is diffusion limited growth. Reaction constants k are 3.73 × 10−7 m/s2, 4.60 × 10−7 m/s2 and 2.45 × 10−7 m/s2, respectively.

Facile synthesis of Bi2S3 nanosheet/Zr:Fe2O3 nanorod heterojunction: Effect of Ag interlayer on the change transport and photoelectrochemical stability

In this work, the hydrothermal approach has been used to prepare and control the morphology of Bi2S3 nanosheet (NS)/Zr doped Fe2O3 nanorod (NR) heterojunction grown on fluorine doped tin oxide (FTO) phoptoelectrodes. The effect of morphology of Bi2S3 NS was examined by comparing the photocatalytic activity of Zr:Fe2O3 nanorod with synthesized heterojunctions. This novel heterojunction photoanode exhibits the light harvesting, the photoinduced electron–hole separation and yielding a maximum photocurrent density of ∼1.27mAcm−2 at −0.4V vs. Ag/AgCl under one sun illumination. Bi2S3 NS on surface of the Zr:Fe2O3 NR will act as the active material which shows the dramatic improvement in photocurrent generation. Further, effect of silver interlayer on the interface properties of Bi2S3 NS/Zr:Fe2O3 NR heterojunction was also studied. The results indicated that the silver interlayer reduces charge recombination at interface of Bi2S3 and Zr:Fe2O3. Also, the surface plasmon resonance of Ag and controlled morphology enhances the performance (1.5mAcm−2 at −0.4V) as well as improves the stability of Bi2S3/Zr:Fe2O3 heterojunction photoelectrode. This unique design of the nanoarchitecture provides an attractive pathway for the photogenerated electrons and the silver interlayers has great impact on enhancing charge separation and improving stability of photoanode.

Flexible Metal/Oxide/Metal Transparent Electrodes Made of Thermally Evaporated MoO3/Ag/MoO3 for Thin Film Heaters

The authors report on thermally‐evaporated MoO3/Ag/MoO3 multilayer films as a flexible and transparent electrode for high performance flexible thin film heaters (TFHs). Using thermal evaporation, the authors obtain highly flexible MoO3/Ag/MoO3 multilayer films on colorless polyimide substrate without plasma damage. To optimize the thickness of the Ag interlayer, the authors investigate the electrical, optical, morphological, and mechanical properties of MoO3/Ag/MoO3 multilayers as a function of Ag interlayer thickness. Based on a figure of merit value, the authors obtain an optimal MoO3/Ag/MoO3 electrode with a low sheet resistance of 3.17 Ohm/square, a high optical transmittance of 77.85%, and critical bending radius of 1 mm, which are acceptable for fabrication of TFHs. The flexible TFHs (25 × 25 mm2) fabricated on a thermally evaporated MoO3/Ag/MoO3 electrode shows a high saturation temperature of 118 °C even at a low input power of 2.5 W (input voltage 2.5 V) due to very low sheet resistance. Successful operation of the flexible TFHs indicate that the thermally‐evaporated MoO3/Ag/MoO3 film is a promising alternative transparent electrode to substitute sputtered Sn‐doped In2O3 (ITO) films for highly transparent and flexible TFHs.

Wide Bandgap Transparent Conducting Electrode of FTO/Ag/FTO Structure for Ultraviolet Light-Emitting Diodes.

We investigated the effect of the Ag interlayer thickness on the structural, electrical and optical properties of FTO/Ag/FTO structures designed for use in wide bandgap transparent conducting electrodes. The top and bottom FTO layers were deposited on α-Al2O3 (0001) substrates via RF magnetron sputtering at 300 °C and Ag interlayers were deposited using an e-beam evaporator system. We optimized the figure of merit by changing the thickness of the inserted Ag interlayer from 10 nm to 14 nm, achieving a maximum value of 2.46 × 10-3 Ω-1 and a resistivity of 6.4 × 10-4 Ω · cm using an FTO (70 nm)/Ag (14 nm)/FTO (40 nm) structure. Furthermore, the average optical transmittance in the deep UV range (300 to 330 nm) was 82.8%.

Measurement-based optimization and analysis of α-IGZO/Ag/α-IGZO transparent conducting electrodes fabricated using DC magnetron sputter deposition

Transparent conducting electrodes have been systematically developed for optoelectronic devices and applications in industry through materials exploration and manufacturing process optimization. The nanostructural, optical and electrical properties were correlated with the embedded Ag interlayer thickness for the first time, for α-IGZO/Ag/α-IGZO trilayer electrodes fabricated using DC magnetron sputter deposition. Optimizing the Ag interlayer thickness at 14 nm achieves a maximum Haacke figure of merit (FOM) of 7.3 × 10−3 Ω−1, at least two orders of magnitude greater than that of the single IGZO film, with X-ray diffraction patterns indicating a crystalline phase that is also retained for thicker layers. Electrical and surface topography measurements confirm a uniform, continuous Ag interlayer film with bulk metallic behavior and resistivity as low as 6 × 10−5 Ω cm. Experimentally-calibrated finite-element modeling and ray tracing simulations unravel in the multilayer films, backscattering and transmission effects from random surface roughness, as well as phonon- or ionized impurity-scattering mediated free carrier absorption plus surface/interface scattering and interference effects. Moreover, film thickness-sensitive tuning of the optical bandgap between 2.98 and 3.14 eV was demonstrated, yielding a maximum bandgap and Haacke FOM at the optimized Ag interlayer thickness, and with many-body interactions outcompeting the Burstein-Moss effect above this thickness.

Improvement of MoO3/Ag/MoO3 multilayer transparent electrodes for organic solar cells by using UV–ozone treated MoO3 layer

Ultraviolet ozone (UVO) treatment of molybdenum trioxide (MoO3) appears to be a simple and efficient method for obtaining highly continuous and smooth silver (Ag) thin films in the thermally evaporated MoO3/Ag/MoO3 (MAM) multilayered structure as transparent electrodes for small-molecule organic solar cells (OSCs). It is observed that UVO treatment can oxidatively modify the non-stoichiometric MoO3 (or MoO3-x) surfaces, further increasing the Mo6+/Mo5+ composition ratio and work function of MoO3-x. Importantly, the use of UVO treatment for the MoO3 bottom layer effectively improves the wettability of Ag on MoO3 and enhances the lateral growth of Ag thin film, resulting in a reduction of the percolation threshold thickness of the continuous Ag layer. Due to the formation of an ultrathin Ag interlayer with a continuous and smooth surface morphology, the MAM multilayered electrode after UVO treatment of MoO3 for 3 min has excellent optical and electrical properties, including a high maximum transmittance of 89.1% and a low sheet resistance of 8.0 Ω/sq. When the optimal UVO-treated MoO3/Ag (7.5 nm)/MoO3 films are used as the anode in OSCs with the copper phthalocyanine (CuPc)/fullerene (C60) planar heterojunction structure, the OSCs have a power conversion efficiency of 0.55%, which is 2.0 and 1.2 times higher than that of devices with untreated MoO3/Ag (7.5 nm)/MoO3 (0.27%) and MoO3/Ag (10 nm)/MoO3 electrodes (0.46%), respectively, and competitive with that of indium-tin-oxide-based devices. Because of almost full surface coverage of the Ag interlayer, UVO treatment of MoO3 in MAM multilayered electrodes can improve charge carrier injection/extraction at the anode contact and hence improve the photovoltaic performance of OSCs.

High quality transparent conductive hydrogenated AZO with embedded Ag films deposited on PEN flexible substrate

The hydrogenated aluminum-doped zinc oxide (HAZO)/Ag/HAZO (HAH) tri-layer structure transparent conductive films (TCFs) have been deposited on polyethylene naphthalate (PEN) flexible substrates via DC magnetron sputtering process and high quality TCFs have been obtained. The effect of Ag interlayer films thickness on crystal structure, electrical conductivity, optical transmittance and mechanical flexibility of HAH tri-layer films was investigated. It is found that the crystallinity of Ag interlayer films increased with the thickness. The results demonstrated that the Ag interlayer thickness was an essential factor for the photoelectric properties of these tri-layer thin films. The optimal tri-layer thin film with 15 nm Ag film exhibited a sheet resistance of 6.37 Ω/sq and an average transmittance of 88.18% in visible region discounting PEN substrate. The bending tests revealed superior flexibility of such multilayer thin films owing to the existence of ductile Ag interlayer films. These tri-layer structure TCFs showed promising potential application for flexible photoelectric devices.

Indium-saving effect and physical properties of transparent conductive multilayers

Indium-free transparent conductive multilayer structures consisting of top and bottom MoO3 layers and an Ag interlayer (MoO3/Ag/MoO3; MAM) are deposited onto glass substrates by vacuum evaporation. The transmittance and sheet resistance of the structures are evaluated, and the optimum structure is determined to be MAM (20/14/30 nm) as it shows the best figure of merit (FOM), which is used as the index for transparent conductive films, with a value of 6.2 × 10-3 Ω-1. To further improve the performance of the films, we attempt to fabricate a multilayer consisting of MoO3 and indium zinc oxide (IZO), based on previous results. The obtained IAM (30/14/50 nm) multilayer shows an FOM higher than that of the MAM, with a value of 32 × 10-3 Ω-1. Moreover, it reduces the amount of required indium as compared with the IZO/Ag/IZO multilayer.

Tunable plasmon-enhanced broadband light harvesting for perovskite solar cells

In this work, we report a reliable method for synthesizing (Au, Au/Ag core)/(TiO2 shell) nanostructures with their plasmonic wavelengths covering the visible light region for perovskite solar cells. The mono- and bi-metallic core-shell nanoparticles exhibit tunable localized surface plasmon resonance wavelength and function as “light tentacle” to improve the photo-electricity conversion efficiency. Plasmonic nanoparticles with different sizes and shapes, different thicknesses of TiO2 shell and Ag interlayer are found to have a strong influence on the localized surface plasmon resonance enhancement effect. The experimental photovoltaic performance of perovskite solar cells is significantly enhanced when the plasmonic nanoparticles are embedded inmesoporous TiO2 scaffolds. A champion photo-electricity conversion efficiency of 17.85% is achieved with nanoparticles (Au/Ag, λLSPR = 650 nm), giving a 18.7% enhancement over that of the pristine device (15.04%). Finite-difference time-domain simulations show that nanorod Au in mesoporus TiO2 scaffold induces the most intense electromagnetic coupling, and provides a novel emitter for photon flux in mesoporous perovskite solar cells. These theoretical results are consistent with the corresponding experimental those. Thus, enhancing the incident light intensities around 650 nm will be most favorable to the improvement of the photo-electricity conversion efficiency of perovskite solar cells.

A Review on Diffusion Bonding between Titanium Alloys and Stainless Steels

High‐quality joints between titanium alloys and stainless steels have found applications for nuclear, petrochemical, cryogenic, and aerospace industries due to their relatively low cost, lightweight, high corrosion resistance, and appreciable mechanical properties. This article reviews diffusion bonding between titanium alloys and stainless steels with or without interlayers. For diffusion bonding of a titanium alloy and a stainless steel without an interlayer, the optimized temperature is in the range of 800–950°C for a period of 60–120 min. Sound joint can be obtained, but brittle FeTi and Fe‐Cr‐Ti phases are formed at the interface. The development process of a joint mainly includes three steps: matching surface closure, growth of brittle intermetallic compounds, and formation of the Kirkendall voids. Growth kinetics of interfacial phases needs further clarification in terms of growth velocity of the reacting layer, moving speed of the phase interface, and the order for a new phase appears. The influence of Cu, Ni (or nickel alloy), and Ag interlayers on the microstructures and mechanical properties of the joints is systematically summarized. The content of FeTi and Fe‐Cr‐Ti phases at the interface can be declined significantly by the addition of an interlayer. Application of multi‐interlayer well prevents the formation of intermetallic phases by forming solid solution at the interface, and parameters can be predicted by using a parabolic diffusion law. The selection of multi‐interlayer was done based on two principles: no formation of brittle intermetallic phases and transitional physical properties between titanium alloy and stainless steel.