Foil Substrates Research Articles

Molten-Li infusion of ultra-thin interfacial modification layer towards the highly-reversible, energy-dense metallic batteries

The practical issues of uncontrollable dendrite growth, infinite volume propagation and dynamic interfacial properties hinder the deployment of the metallic anodes in the realistic energy-dense batteries. In this study, an ultra-thin (6.3 µm), lightweight (0.35 mg cm-2), dual-functionalized composite layer that derived from the ZIF-67@ZIF-8 core-shell structure effectively modifies the Cu foil substrate (denoted as the Co@Zn-CNT-Cu). The interfacial engineering deliberately involves the atomically distributed Zn species riveted on the exterior surface of the carbonaceous units; meanwhile the in-situ grown carbon nanotubes (CNTs) threaded from the interior Co-centers reinforce the structural integrity of the dodecahedron storage units. As the Co@Zn-CNT-Cu substrate with the precise control over the molten-Li infusion (0.5×excess) integrates with the LiNi0.8Mn0.1Co0.1O2 (NMC-811) cathode (10.80 mg cm-2) in a single-layer pouch cell, the prototype exhibits the enhanced cycling reversibility and Li utilization degree with operando phase tracking via transmission-mode X-ray diffraction. The interfacial engineering of the substrate with the controlled molten-Li infusion thus presents a promising strategy to harness the energy-dense merits of metallic batteries.

Copper foil after hydrothermal treatment in acidified tungstate solution as conductor- and binder-Free anode electrodes for high performance lithium-ion batteries

Copper foil is commonly used as anode current collector in the battery industry due to its high conductivity, good elasticity and relative abundance. Herein, copper foil was hydrothermally treated in acidified tungstate solution, resulting in the formation of Cu2O and WO3 agglomerated clusters on the copper foil substrate with sufficient open space between neighboring clusters. The copper foil after hydrothermal treatment was directly used as the conductor- and binder-free anode electrode for lithium-ion batteries. Cyclic voltammetry and charge-discharge measurements were performed to investigate the reversible areal capacity, cycling stability and rate capability of the as-prepared electrode. A reversible areal capacity of 357 μAh cm−2 was obtained after 50 cycles at a current density of 60 μA cm−2. Even cycled at a current density of 600 μA cm−2, a reversible capacity of 8 μAh cm−2 remained. When the current density returns to 60 μA cm−2, the conductor- and binder-free electrode exhibits an areal discharge capacity of 430 μAh cm−2.

A Flexible Chip-Film Patch and a Flexible Strain Gauge Sensor Suitable for a Hybrid System-in-Foil Integration

Hybrid Systems-in-Foil (HySiF) encompass large-area thin-film electronics and ultrathin, high performance CMOS chips, which are integrated into a flexible polymeric foil substrate. In this work, the individual components of a customized flexible sensor system are characterized in detail, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i.e.</i> , a strain gauge and a readout ASIC, and the system functionality is proved. We employ the Chip-Film Patch (CFP) technology, where an ultra-thin readout ASIC is embedded in spin-coated polyimide foil in order to monitor resistance variations of strain gauges. These two components are suitable to be integrated on the same foil, whereas the envisioned system is intended to monitor the respiratory system of newborns and premature infants. The latest developments in the CFP process using the aromatic polyimide PI-2611 are shown. In particular, the optimization of the spin-coating and evaluation of polyimide uniformity above the embedded chip are highlighted. Furthermore, we demonstrate a flexible strain gauge sensor using thin-film metals embedded in polyimide PI-2611, which is usable at up to 30% strain under electromechanical load. This also demonstrates the mechanical reliability of the CFP circuit interconnects. The electrical characterization of the readout ASIC, after back-thinning and embedding into the CFP, reveals no stress induced performance degradation.

Fabrication of Graphene/Zinc Oxide Nano-Heterostructure for Hydrogen Sensing.

In this study, hydrogen (H2) and methane (CH4) were used as reactive gases, and chemical vapor deposition (CVD) was used to grow single-layer graphene on a copper foil substrate. The single-layer graphene obtained was transferred to a single-crystal silicon substrate by PMMA transfer technology for the subsequent growth of nano zinc oxide. The characteristics of CVD-deposited graphene were analyzed by a Raman spectrometer, an optical microscope, a four-point probe, and an ultraviolet/visible spectrometer. The sol–gel method was applied to prepare the zinc oxide seed layer film with the spin-coating method, with methanol, zinc acetate, and sodium hydroxide as the precursors for growing ZnO nanostructures. On top of the ZnO seed layer, a one-dimensional zinc oxide nanostructure was grown by a hydrothermal method at 95 °C, using a zinc nitrate and hexamethylenetetramine mixture solution. The characteristics of the nano zinc oxide were analyzed by scanning electron microscope(SEM),x-ray diffractometer(XRD), and Raman spectrometer. The obtained graphene/zinc oxide nano-heterostructure sensor has a sensitivity of 1.06 at a sensing temperature of 205 °C and a concentration of hydrogen as low as 5 ppm, with excellent sensing repeatability. The main reason for this is that the zinc oxide nanostructure has a large specific surface area, and many oxygen vacancy defects exist on its surface. In addition, the P–N heterojunction formed between the n-type zinc oxide and the p-type graphene also contributes to hydrogen sensing.

Supercapacitor electrodes based on modified titania nanotube arrays on flexible substrates

Abstract Highly ordered titania nanotube arrays were synthesised on titanium metal foil through electrochemical anodisation. The annealed samples were characterised through scanning electron microscopy and X-ray diffraction analysis. The electrochemical characterisations of the arrays were done through cyclic voltammetry, galvanostatic charge discharge and electrochemical impedance spectroscopy analyses. The titania nanotube arrays exhibited a specific capacitance of 6.8 mF cm–2 at 5 mV s–1 scan rate, which is very much higher than that reported earlier. Pseudocapacitive metal oxides were deposited on these arrays forming composite supercapacitor electrodes and their supercapacitor properties were compared with same deposited on bare titanium foil substrates. Pseudocapacitive metal oxides deposited on these titania nanotube array substrates exhibited improved supercapacitor performance and stability over the same deposited on titanium foil substrates.

An experimental investigation of ZnO nanostructures on various substrates using electrodeposition method

In this study, zinc oxide (ZnO) nanostructures were fabricated on the fluorine doped tin-oxide (FTO) glass and zinc (Zn) foil substrates by the electrodeposition method. After the preparation, ZnO nanostructures were characterized by Fourier transform infra-red (FTIR), fluorescence (FL) spectroscopy, field emission scanning electron microscopy (FESEM) and energy dispersive x-ray (EDX) spectroscopy, respectively. FTIR spectra confirmed the presence of Zn-O stretching vibrational modes at 445 cm−1 and the FL emission spectrum of both samples revealed the highest quenching fluorescence emission at ∼650 nm with the excitation wavelength of 320 nm. Further, the FESEM morphological images showed the well-defined and uniformly grown nanostructures (nanorod, nanowire and cauliflower-like structures) on the substrates. It was shown the diameter of the ZnO nanorods on FTO and ZnO cauliflower-like on Zn foil varies at 19.56–60.89 nm and 50.41–76.4 nm. Finally, EDX spectra endorsed the presence of ‘Zn’ and ‘O’ elements on the samples.

Controlled synthesis of luminescent ZnS nanosheets with high piezoelectric performance for designing mechanical energy harvesting device

For the first time, single-step fabrication of two-dimensional nanosheets of zinc sulfide (ZnS) was achieved employing flexible aluminum (Al) foil substrate using hydrothermal technique at 140 °C for ∼4 h. Indium doped Tin Oxide (ITO) coated on PET (Polyethylene Terephthalate) substrate and ZnS deposited Al foil as a top and bottom electrodes were used to fabricate a piezoelectric device. To generate an electric potential, the top ITO electrode was tapped on the ZnS nanosheets. The open-circuit voltage, VOC of ∼400 mV was obtained and analyzed for ZnS nanosheets based nanogenerator with gentle finger taping. However, the highest output for the single nanogenerator was found to be ∼600 mV by applying toe pressure. Additionally, switching polarity and superposition experiments were utilized to confirm the nanogenerator's performance, with the findings confirming piezo-electric voltage output. This study investigates the new potential for a ZnS-based high-efficient energy harvester that can scavenge biomechanical energy for next-generation flexible self-powered electronics devices as well as a good replacement for ZnO nanosheets in 2D nanostructured based nanogenerator devices due to its simple single-step production process, low cost, and high output gain.

Photonic response and temperature evolution of SiO2/TiO2 multilayers

The microstructural and optical reflectivity response of photonic SiO2/TiO2 nanomultilayers have been investigated as a function of temperature and up to the material system’s melting point. The nanomultilayers exhibit high, broadband reflectivities up to 1350 °C with values that exceed 75% for a 1 μm broad wavelength range (600–1600 nm). The optimized nanometer sized, dielectric multilayers undergo phase transformations from anatase TiO2 and amorphous SiO2 to the thermodynamically stable phases, rutile and cristobalite, respectively, that alter their structural morphology from the initial multilayers to that of a scatterer. Nonetheless, they retain their photonic characteristics, when characterized on top of selected substrate foils. The thermal behavior of the nanometer sized multilayers has been investigated by differential thermal analysis (DTA) and compared to that of commercially available, mm-sized, annealed powders. The same melting reactions were observed, but the temperatures were lower for the nm-sized samples. The samples were characterized using X-ray powder diffraction before DTA and after annealing at temperatures of 1350 and 1700 °C. The microstructural evolution and phase compositions were investigated by scanning electron microscopy and energy-dispersive X-ray spectroscopy measurements. The limited mutual solubility of one material to another, in combination with the preservation of their optical reflectivity response even after annealing, makes them an interesting material system for high-temperature, photonic coatings, such as photovoltaics, aerospace re-entry and gas turbines, where ultra-high temperatures and intense thermal radiation are present.

The current hysteresis effect of tower-like MoS2 nanocrystalline film for field emission and memristor applications

In this work, we investigate the hysteresis effect of the current-voltage characteristic for the magnetron sputtered molybdenum disulfide (MoS2) nanocrystalline films. The field emission hysteresis of MoS2 cold cathode is studied by sweeping mode with voltage upward/downward, the vacuum pressure has a remarkable effect on the hysteresis of the emission current and overall the hysteresis becomes more prominent as pressure rises. Besides, we also demonstrate the current-voltage behaviors of MoS2 film using thermal evaporated Al dot as top electrode and copper foil substrate as bottom electrode. The Al/MoS2/Cu configuration device presents an obvious current hysteretic effect and the current increases with the increase of the voltage sweeping times. The possible mechanism of the hysteresis has been proposed herein and also investigations provide a great promise for the development of magnetron sputtered MoS2 nanocrystalline films in applications such as field emitters and memristor devices.

Space-Filling Curve Resistor on Ultra-Thin Polyetherimide Foil for Strain Impervious Temperature Sensing.

Monitoring process parameters in the manufacture of composite structures is key to ensuring product quality and safety. Ideally, this can be done by sensors that are embedded during production and can remain as devices to monitor structural health. Extremely thin foil-based sensors weaken the finished workpiece very little. Under ideal conditions, the foil substrate bonds with the resin in the autoclaving process, as is the case when polyetherimide is used. Here, we present a temperature sensor as part of an 8 µm thick multi-sensor node foil for monitoring processing conditions during the production and structural health during the lifetime of a construction. A metallic thin film conductor was shaped in the form of a space-filling curve to suppress the influences of resistance changes due to strain, which could otherwise interfere with the measurement of the temperature. FEM simulations as well as experiments confirm that this type of sensor is completely insensitive to the direction of strain and sufficiently insensitive to the amount of strain, so that mechanical strains that can occur in the composite curing process practically do not interfere with the temperature measurement. The temperature sensor is combined with a capacitive sensor for curing monitoring based on impedance measurement and a half-bridge strain gauge sensor element. All three types are made of the same materials and are manufactured together in one process flow. This is the key to cost-effective distributed sensor arrays that can be embedded during production and remain in the workpiece, thus ensuring not only the quality of the initial product but also the operational reliability during the service life of light-weight composite constructions.

Dimension- and position-controlled growth of GaN microstructure arrays on graphene films for flexible device applications

This paper describes the fabrication process and characteristics of dimension- and position-controlled gallium nitride (GaN) microstructure arrays grown on graphene films and their quantum structures for use in flexible light-emitting device applications. The characteristics of dimension- and position-controlled growth, which is crucial to fabricate high-performance electronic and optoelectronic devices, were investigated using scanning and transmission electron microscopes and power-dependent photoluminescence spectroscopy measurements. Among the GaN microstructures, GaN microrods exhibited excellent photoluminescence characteristics including room-temperature stimulated emission, which is especially useful for optoelectronic device applications. As one of the device applications of the position-controlled GaN microrod arrays, we fabricated light-emitting diodes (LEDs) by heteroepitaxially growing InxGa1−xN/GaN multiple quantum wells (MQWs) and a p-type GaN layer on the surfaces of GaN microrods and by depositing Ti/Au and Ni/Au metal layers to prepare n-type and p-type ohmic contacts, respectively. Furthermore, the GaN microrod LED arrays were transferred onto Cu foil by using the chemical lift-off method. Even after being transferred onto the flexible Cu foil substrate, the microrod LEDs exhibited strong emission of visible blue light. The proposed method to enable the dimension- and position-controlled growth of GaN microstructures on graphene films can likely be used to fabricate other high-quality flexible inorganic semiconductor devices such as micro-LED displays with an ultrahigh resolution.

Magnetic force enhanced atmospheric plasma polishing ability to improve surface roughness of copper base materials

The global demand for portable miniature products has increased, which has driven the improvement of micro-component technology to meet the precision requirements of miniaturization of product sizes and higher precision of products. As the requirements for the assembly accuracy of precision components and the high quality on the surface treatment of materials, the current precision polishing is also facing a technical bottleneck. Many polishing technologies have been developed, atmospheric plasma polishing is a new polishing technology, which is applied to the precision components of the optoelectronic industry. How to improve the polishing efficiency of atmospheric plasma has become a new research topic. In this study, a non-traditional surface treatment method which low-temperature atmospheric plasma is used to precision polish the copper-based material, and added magnetic force on the surface of the copper-based material, in order to enhanced atmospheric plasma polishing ability to improve surface roughness of copper base materials. The low-temperature atmospheric plasma jet has been used; the power of plasma is 50Wand nitrogen (N2) as reaction gas. The different scanning speed of stages is 2, 5, 10, 15 and 20 mm/s, respectively. The processing time is 10min. A copper foil substrate is as select material. Observe the surface roughness variation of the copper foil substrate treated by atmospheric plasma. The results shown that when the copper foil substrate is treated with low-temperature atmospheric plasma and no magnetic force on the surface, when the scanning speed of the stage is 2 mm/min, the improvement rate of surface roughness is about 17.6%; when the scanning speed of the stage is 20 mm/min, the surface roughness improvement rate is about 5.5%. When the magnetic force on the surface is about 188 mT, the improvement rate of surface roughness is about 30.8% when the scanning speed of the stage is 2 mm/min, and the improvement rate of surface roughness is about 12.5 % when the scanning speed of the stage is 20 mm/min. From the above results, it is known that applying magnetic force on the surface of the work-piece can indeed increase and improve the polishing ability of the low-temperature atmospheric plasma.

Coat multi-layered graphene on Cu with radiofrequency plasmas for anti-oxidization in hot air

Direct and fast synthesis of protective coating on metal surfaces is a major challenge in anti-corrosion applications of 2D graphene. In this article, we provided an approach to this challenge by using radiofrequency plasmas, where the mixture of CH4/H2 or pure CH4 gases can be decomposed under low temperature while the temperature of the Cu foil substrates can still be kept high by the induced eddy current. The high substrate temperature is essential for enhancing graphene quality, but many other plasma synthesis techniques seldom addressed this point. Graphene coatings with thicknesses of about 30 nm could be obtained in 3.5 min. Anti-corrosion tests examine protection coatings under various conditions. In this article, we mainly checked the protection performance of the graphene coatings against Cu oxidization in air. Anti-oxidization tests under 300 °C for 360 min proved that the coatings synthesized with pure CH4 performed better over those synthesized with mixture of CH4/H2. Tests under 200 °C for 900 min and 22 °C for 111 days demonstrated that the coatings synthesized with different gas compositions had equivalent anti-oxidization capabilities. Our calculations with density functional theory revealed that the defective single-layered graphene was unable to protect the Cu substrate, and it would be better to use multi-layered graphene in practice. The synthesis technique in this article could also be used in many other areas beyond anti-oxidization such as chemical reaction catalysis, electrode materials, electromagnetic interference shielding and so on.

Manganese vanadium sulfate-oxide cylindrical core-shell heterostructures by electro-spray deposition on graphite foil for Li+ ion intercalation

Heterostructure based on metal sulfides and oxides nanomaterials can be relevant to the charge storage devices. Here, we show that Mn(CH3COO)2·4H2O and VOSO4·xH2O can react in ethanol/water droplets generated by an electric field assisted spray system, so that MnSx-VSx/MnzV2O5 heterostructures in the shape of nanometric cylindrical particles can be deposited on a graphite foil substrate. The composite material phases were detected by several microscopies and microscopic probes spectroscopies, i.e., micro-Raman and scanning X-ray photoemission microscopy. The nanometric cylindrical particles were relatively homogenously distributed throughout the film covering the graphite foil. Film thickness modulation on surface was calculated between 100 and 300 nm range. We show that the segregation of MnV-O and MnV-S relative abundance in the internal and external volume of the cylindrical nanoparticles respectively, can be exploited during faradaic and non-faradaic processes in charge/discharge.

Unique role of dimeric carbon precursors in graphene growth by chemical vapor deposition

Chemical vapor deposition has emerged as a promising approach for high-quality graphene synthesis. Graphene quality, including the defect density, the size of monocrystal domains, and the number of layers, depend on the growth conditions. The main experimental parameters include temperature, metal catalyst composition, growth atmosphere, and gaseous dynamics in the reaction chamber. Here we show, that even for the same growth conditions, simply changing carbon source from methane to ethane or acetylene yields drastically different growth mode that allows the production of single-crystal-like graphene on a polycrystalline metal foil substrate. This new single crystal growth mechanism does not require local supply of carbon precursors or special single crystal catalytic substrate that were introduced earlier. We assign the observed differences in the growth mechanism to formation of stable and mobile dimeric C2Hx intermediate species from ethane and acetylene, in contrast to less mobile CHx and C3Hx species formed from methane and propane.

Understanding interface evolution during explosive welding of silver foil and Q235 substrate through experimental observation coupled with simulation

In this work, explosive welding was introduced to manufacture Ag coating on Fe substrate. The microstructure evolutions of the Ag/Fe joint interface and the associated governing mechanisms during the collision process, were investigated by a comprehensive study combined advanced characterizations and smoothed particles hydrodynamics simulations. It was concluded that the self-developed explosive welding process enabled to attain high-quality Ag coatings effectively, certified by absence of geometric defects at the Ag/Fe interface and the surface of Ag foil. The simulation accurately reproduced the wavy interface and vortex structure observed in experiment. From this, the evolution of the wave was reconstructed and the formation mechanism of the vortex was revealed. The microstructure analyses revealed a remarkable diversity of the grain structure near the Ag/Fe interface. The equiaxed fine grains related to dynamic recrystallization were formed in the vicinity of the interface and also within the vortex. The grains of the Fe matrix slightly away from the interface became elongated, which reflected well the deformation features. Meanwhile, the columnar grains induced by molten and re-solidified processes were observed at the vortex boundary. The variation of these grain structures was responsible for the inhomogeneity of nanoindentation hardness distribution.

Treatment of NiMoO4/nanographite nanocomposite electrodes using flexible graphite substrate for aqueous hybrid supercapacitors.

The cycling performance of supercapacitors sometimes becomes limited when electrode materials slough off during frequent charge–discharge cycles, due to weak bonding between the active material and the current collector. In this work, a flexible graphite foil substrate was successfully used as the current collector for supercapacitor electrodes. Graphite foil substrates were treated in different ways with different acid concentrations and temperatures before being coated with an active material (NiMoO4/nanographite). The electrode treated with HNO3 (65%) and H2SO4 (95%) in a 1:1 ratio at 24°C gave better electrochemical performance than did electrodes treated in other ways. This electrode had capacitances of 441 and 184 Fg–1 at current densities of 0.5 and 10 Ag-1, respectively, with a good rate capability over the current densities of the other treated electrodes. SEM observation of the electrodes revealed that NiMoO4 with a morphology of nanorods 100–120 nm long was properly accommodated on the graphite surface during the charge–discharge process. It also showed that treatment with high-concentration acid created an appropriately porous and rough surface on the graphite, enhancing the adhesion of NiMoO4/nanographite and boosting the electrochemical performance.

Fabrication of Ag micro-particles based on stress-induced migration by using multilayered structure with artificial holes array.

Silver micro/nanomaterials have attracted a great deal of attention due to their superior physicochemical properties. The atomic migration driven by electromigration or stress-induced migration has been demonstrated to be a promising method for the fabrication of metallic micro-/nanomaterials because of the advantage of simple processing. However, how to realize the controllable fabrication and mass production is still the critical technical problem for the method to be used in large-scale industrial applications. In this paper, the multilayered samples consisted of copper foil substrate, Ti adhesive layer, Ag film, and TiN passivation layer and with arrays of artificial holes on the passivation layer were applied to prepare arrays of Ag micro-particles. For the purpose of controllable fabrication, stress-induced migration experiments combined with finite element simulation were applied to analyze the influence of the passivation layer thickness and the heating temperature on the atom migration and Ag particles growing behavior. And the relationship between size of the fabricated Ag particles and the processing parameters of stress-induced migration experiments were also investigated. As a result, a proper structure size of the multilayered samples and heating temperature were recommended, which can be used for the Ag micro-particles controllable fabrication and mass production.

Intagliated Cu substrate containing multifunctional lithiophilic trenches for Li metal anodes

Lithiophilic 3D substrates for lithium metal anodes (LMAs) are attracting considerable attention because they can provide an extensive active surface area and electrolyte reservoir for reversible lithium metal storage. However, the introduction of additional 3D-structured electrode materials on a typical Cu foil substrate decreases the specific/volumetric capacities of LMA. Herein, we report an alternative intagliated Cu foil (I-Cu) substrate with lithiophilic trenches that can be prepared through a mass-scalable photoresist process followed by simple chemical treatments. The patterned trenches are covered with nanocrevices, including numerous oxygen functional groups (O/Cu ratio of 1.00) and nanopores, extensively widening the electrochemical active surface area (EASA) of the I-Cu substrate by > 30 times that of a typical 2D Cu foil. The nanostructure, high surface area, lithiophilic surface properties, and intagliated trenches of the I-Cu substrate serve to guide preferred lithium metal nucleation and growth behavior on the controlled active surfaces. Accordingly, highly efficient and stable cycling performances were accomplished for the LMA composed of the I-Cu substrate over 500 cycles with an average Coulombic efficiency of ∼ 99%. Moreover, the feasibility of the I-Cu-based LMA was demonstrated in the full cell tests with typical cathode materials, NCM622 and a sulfur copolymer.

Formulation and characterization of screen printable dopant ink for fabrication of polysilicon TFTs

To move the promise of printed electronics from the laboratory to volume production required adopting a new approach eliminating ink-jet printing and adopting instead a hybrid mature print and conventional process. Novel screen printable N+ and P+ dopant inks were developed to fabricate polysilicon thin film transistors (TFTs). Semiconductor-grade dopant inks were formulated from a combination of thermoset plastic with boron and phosphor compounds. Inks were screen printed on polysilicon active islands on a 300 mm square stainless-steel foil substrate. The drain and source of the top gate TFTs were then formed via a thermal anneal activation. The residue after annealing was removed with an inoffensive process to avoid damage to the thin silicon layer and gate oxide. Doping was uniform across 300 mm sheet substrate. The sheet resistance was modulated to 200 Ω sq−1 for the N+ and 1000 Ω sq−1 for the P+ active layer. Field mobility of polysilicon TFTs fabricated using this screen-printed dopant process were 80 cm2V s−1 for PMOS and 200 cm2V s−1 for NMOS using low-cost, mature equipment, and an easily manageable process that is both scalable and compatible with roll-to-roll manufacturing.