Method For Large-scale Fabrication Research Articles

Effect of spraying power on the microstructure and thermoelectric performance of plasma sprayed higher manganese silicides films

Higher manganese silicides (HMS) are deemed as particularly promising p-type thermoelectric materials. Apart from considerations in the materials available, the difficulty in converting them into engineering devices also limits thermoelectric applications. Atmospheric plasma spraying, as a flexible and cost-effective manufacturing process, was employed to produce thermoelectric films. In this study, HMS films were deposited using atmospheric plasma spray under controlled spraying power with different thermal exposures. The as-sprayed HMS films were characterized not only for phase and microstructure, but also for temperature dependent electrical conductivity and Seebeck coefficient. The power factor was calculated to assess the effect of spraying power on thermoelectric performance. The results show that the spraying power not only affects the melt state of the HMS particles, which leads to the variation of the microstructure of the films, but also its stoichiometry associated with phase transformation during spraying process. The maximum power factor value of 156.90 μW m−1 K−2 was acquired at 500 °C for HMS film deposited with the lowest spraying power. The results provide a large-scale fabrication method to improve the potential applicability of thermoelectric films.

Wafer-Scale Fabrication of High-Performance n-Type Polymer Monolayer Transistors Using a Multi-Level Self-Assembly Strategy.

Wafer-scale fabrication of high-performance uniform organic electronic materials is of great challenge and has rarely been realized before. Previous large-scale fabrication methods always lead to different layer thickness and thereby poor film and device uniformity. Herein, the first demonstration of 4 in. wafer-scale, uniform, and high-performance n-type polymer monolayer films is reported, enabled by controlling the multi-level self-assembly process of conjugated polymers in solution. Since the self-assembly process happened in solution, the uniform 2D polymer monolayers can be facilely deposited on various substrates, and theoretically without size limitations. Polymer monolayer transistors exhibit high electron mobilities of up to 1.88 cm2 V-1 s-1 , which is among the highest in n-type monolayer organic transistors. This method allows to easily fabricate n-type conjugated polymers with wafer-scale, high uniformity, low contact resistance, and excellent transistor performance (better than the traditional spin-coating method). This work provides an effective strategy to prepare large-scale and uniform 2D polymer monolayers, which could enable the application of conjugated polymers for wafer-scale sophisticated electronics.

Fabricating a Mn3O4/Ni(OH)2 Nanocomposite by Water-Boiling Treatment for Use in Asymmetric Supercapacitors as an Electrode Material

The electrode material is the key factor for developing asymmetric supercapacitors. A simple water-boiling treatment was adopted to fabricate a Mn3O4/Ni(OH)2 nanocomposite on a large scale, which exhibited a splendid electrochemical performance with a boiling time of 3 h, achieving a capacitance of 742 F g–1 at 1 A g–1. When assembling the asymmetric capacitor with the Mn3O4/Ni(OH)2 composite and activated carbon separately as positive and negative electrodes, a capacitance of 43 F g–1 was attained at 0.2 A g–1 with an energy density of 15.3 Wh kg–1 at a power density of 168.8 W kg–1. This simple, reproducible, ecofriendly, and large-scale fabrication method is practical for preparing other transition metal oxides for the purpose of use in asymmetric supercapacitors with superior properties.

High index dielectric metasurfaces and colloidal solutions: from fabrication to application

High index dielectric nanoparticles and meta-materials have been proposed for many different applications, including light harvesting, sensing and metalenses. However, widespread utilization in practice also requires large-scale fabrication methods able to produce homogeneous structures with engineered optical properties in a cost effective manner. Here, it is presented a facile fabrication method for silicon nanoparticles which is scalable to 4-inch wafers and can produce a wide range of nanoparticle shapes on demand. We also show that the fabricated nanoparticles can be detached from their support using a simple substrate removal technique and then transferred to colloidal suspension. We will finally discuss some uses of the fabricated systems. For the metasurfaces, we will demonstrate complete absorption due to far field interference effects. For the nanoparticles colloids we will show the possibility of realizing an intrinsically chiral structure composed of a low-loss dielectric resonator and we will study optical trapping phenomena for different particle sizes and shapes.

Gradient structure based dual-robust superhydrophobic surfaces with high-adhesive force

Dual-robust (mechanical and chemical robust) superhydrophobic surfaces with a high adhesive state have aroused lots of attention for their potential application in liquid transportation, biochemical separation and in situ detection devices. Herein, we design a gradient structure based multi-scale micro- and nano-structures (inorganic-organic interpenetrating structures, self-similar sacrificial structures and micro-nano structures) to realize dual robust superhydrophobic surfaces by spraying method. Upon changing the fabrication process, three kinds of superhydrophobic surfaces were made based on benzoxazine, mesoporous SiO2 and imidazole. A rigorous sandpaper abrasion test, chemical resistance test (pH = 1–14, 12 h) and anticorrosion test were carried out to exhibit the environmental stability of the system. High adhesive properties of surfaces were demonstrated by adhering water test. The clear multi-scale structures are showed and its relationship with properties is built. Scanning electron microscope was used to examine different structures and the gradient structure in system. The gradient structure based dual-robust superhydrophobic surfaces give a promising prospect for water transportation application in their large-scale and low-cost fabrication method and super mechanical and chemical robust.

Poly(ionic liquid)s Based Brush Type Nanomotor.

A brush type nanomotor was fabricated via assembly assistant polymerization of poly(ionic liquid) and surface grafting polymerization. The method for large-scale fabrication of brush nanomotors with soft surfaces is described. These soft locomotive particles are based on core-shell brush nanoparticles assembled from poly(ionic liquid) as core and thermoresponsive PNIPAM as brush shells on which platinum nanoparticle (PtNP) were grown in situ. The particles show non-Brownian motion in H2O2 solution.

Antigen-Directed Fabrication of a Multifunctional Nanovaccine with Ultrahigh Antigen Loading Efficiency for Tumor Photothermal-Immunotherapy.

Current antigen-encapsulated multifunctional nanovaccines for oncotherapy suffer from limited antigen loading efficiency, low yield, tedious manufacture, and systemic toxicity. Here, an antigen-directed strategy for the fabrication of multifunctional nanovaccine with ultrahigh antigen loading efficiency in a facile way for tumor photothermal-immunotherapy is shown. As a proof of concept, a model antigen ovalbumin (OVA) is used as a natural carrier to load a representative theranostic agent indocyanine green (ICG). Mixing OVA and ICG in aqueous solution gives the simplest multifunctional nanovaccine so far. The nanovaccine owns antigen loading efficiency of 80.8%, high yield of >90%, intense near-infrared absorption and fluorescence, excellent reproducibility, good aqueous solubility and stability, and favorable biocompatibility. These merits not only guarantee sensitive labeling/tracking and efficient stimulation of dendritic cells, but also reliable imaging-guided photothermal-immunotherapy of tumors and tumor prevention. The proposed strategy provides a facile and robust method for large-scale and reproducible fabrication of multifunctional nanovaccines with ultrahigh antigen loading efficiency for tumor therapy.

Fabrication of Suspended III-V Nanofoils by Inverse Metal-Assisted Chemical Etching of In0.49Ga0.51P/GaAs Heteroepitaxial Films.

Metal-assisted chemical etching (MacEtch) has been established as a low-cost, benchtop, and versatile method for large-scale fabrication of semiconductor nanostructures and has been heralded as an alternative to conventional top-down approaches such as reactive-ion etching. However, extension of this technique to ternary III-V compound semiconductor alloys and heteroepitaxial systems has remained relatively unexplored. Here, Au-assisted and inverse-progression MacEtch (I-MacEtch) of the heteroepitaxial In0.49Ga0.51P/GaAs material system is demonstrated, along with a method for fabricating suspended InGaP nanofoils of tunable thickness in solutions of hydrofluoric acid (HF) and hydrogen peroxide (H2O2). A comparison between Au- and Cr-patterned samples is used to demonstrate the catalytic role of Au in the observed etching behavior. Vertical etch rates for nominally undoped, p-type, and n-type InGaP are determined to be ∼9.7, ∼8.7, and ∼8.8 nm/min, respectively. The evolution of I-MacEtch in the InGaP/GaAs system is tracked, leading to the formation of nanocavities located at the center of off-metal windows. Upon nanocavity formation, additional localized mass-transport pathways to the underlying GaAs substrate permit its rapid dissolution. Differential etch rates between the epilayer and substrate are exploited in the fabrication of InGaP nanofoils that are suspended over micro-trenches formed in the GaAs substrate. A model is provided for the observed I-MacEtch mechanism, based on an overlap of neighboring injected hole distribution profiles. The nanofabrication methodology shown here can be applied to various heteroepitaxial III-V systems and can directly impact the conventional processing of device applications in photonics, optoelectronics, photovoltaics, and nanoelectronics.

Large-scale fabrication of free-standing and sub-μm PDMS through-hole membranes.

Free-standing polydimethylsiloxane (PDMS) through-hole membranes have been studied extensively in recent years for chemical and biomedical applications. However, robust fabrication of such membranes with sub-μm through-holes, and at a sub-μm thickness over large areas is challenging. In this paper, we report a robust and simple method for large-scale fabrication of free-standing and sub-μm PDMS through-hole membranes, combining soft-lithography with reactive plasma etching techniques. First, arrays of sub-μm photoresist (PR) columns were patterned on another spin-coated sacrificial PR layer, using conventional photolithography processes. Subsequently, a solution of PDMS : hexane at a 1 : 10 ratio was spin-coated over these fabricated arrays. The cured PDMS membrane was etched in a plasma mixture of sulfur hexafluoride (SF6) and oxygen (O2) to open the through-holes. This PDMS membrane can be smoothly released with a supporting ring by completely dissolving the sacrificial PR structures in acetone. Using this fabrication method, we demonstrated the fabrication of free-standing PDMS membranes at various sub-μm thicknesses down to 600 ± 20 nm, and nanometer-sized through-hole (810 ± 20 nm diameter) densities, over areas as large as 3 cm in diameter. Furthermore, we demonstrated the potential of the as-prepared membranes as cell-culture substrates for biomedical applications by culturing endothelial cells on these membranes in a Transwell-like set-up.

A general method for large-scale fabrication of Cu nanoislands/dragonfly wing SERS flexible substrates**Project supported by the Youth Fund Project of University Science and Technology Plan of Hebei Provincial Department of Education, China (Grant No. QN2015004) and the Doctoral Fund of Yanshan University, China (Grant No. B924).

Noble metal nanorough surfaces that support strong surface-enhanced Raman scattering (SERS) is widely applied in the practical detection of organic molecules. A low-cost, large-area, and environment-friendly SERS-active substrate was acquired by sputtering inexpensive copper (Cu) on natural dragonfly wing (DW) with an easily controlled way of magnetron sputtering. By controlling the sputtering time of the fabrication of Cu on the DW, the performance of the SERS substrates was greatly improved. The SERS-active substrates, obtained at the optimal sputtering time (50 min), showed a low detection limit (10−6M) to 4-aminothiophenol (4-ATP), a high average enhancement factor (EF, , excellent signal uniformity, and good reproducibility. In addition, the results of the 3D finite-difference time-domain (3D-FDTD) simulation illustrated that the SERS-active substrates provided high-density “hot spots”, leading to a large SERS enhancement.

Synthesis of a nanocomposite consisting of Cu2O and N-doped reduced graphene oxide with enhanced electrocatalytic activity for amperometric determination of diethylstilbestrol

The authors report on a low temperature method for large-scale fabrication of cuprous oxide nanocubes deposited on nitrogen-doped reduced graphene oxide (Cu2O/N-RGO). The material was deposited in a glassy carbon electrode (GCE) where it is found to display enhanced electrocatalytic activity for oxidation of diethylstilbestrol (DES). The morphology and composition of Cu2O/N-RGO were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and energy-dispersive spectroscopy. The results demonstrate that the RGO is doped with 3.5% of nitrogen (atomic ratio), and that nanostructured Cu2O particles with controlled cubical morphology and an average size of about 450 nm have been homogeneously deposited on the surface of N-RGO sheets. The oxidation peak of DES was recorded at 0.315 V (vs. saturated calomel electrode) using differential pulse voltammetry. Under the optimal conditions, the modified GCE displays a linear response in the 0.3 to 150 μM DES concentration range, and the limit of detection is 10 nM. The method was applied to the determination of DES in spiked milk, meat and urine samples and gave excellent selectivity, stability and reproducibility.

Facile, robust and large-scale fabrication method of mechanically durable superhydrophobic PDMS/aerogel coating on fibrous substrates

A simple method was developed for the large-scale fabrication of mechanically durable superhydrophobic surfaces with roughness on the microscale. The method is applicable for a large number of fibrous substrates with different pore sizes. With this method, it is possible to prepare polymeric fibrous substrates with a water droplet (5 μL) roll-off angle of less than 5°. The method developed is based on dip-coating of fibrous substrates in polydimethylsiloxane (PDMS)/toluene solution, followed by the electrostatic spray of aerogel microparticles on the samples. Depending on the PDMS solution concentration, it is possible to obtain a superhydrophobic surface with dual-scale roughness on the microscale. In this article, preparation and characterization of surfaces with electrostatic powder spray on the common fibrous cellulose substrates are provided. Fibrous surfaces obtained were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy and static water contact angle measurement. Effects of PDMS/toluene solution concentration on the surface morphology and wettability behavior of surfaces were investigated. We demonstrate the mechanical durability of the surface using high-pressure air flow.

A General Method for Large-Scale Fabrication of Semiconducting Oxides with High SERS Sensitivity.

Surface-enhanced Raman spectroscopy (SERS) is a versatile and powerful spectroscopic technique for substance analysis and detection. So far, the highest detection sensitivities have been realized on noble nanostructure substrates, which, however, are costly, unstable, and non-biocompatible. While semiconductor substrates could in principle be used, existing realizations have either resulted in substrates with low sensitivities or used methods that have poor technical control. Here we report a general and versatile method, based on ion irradiation and vacuum annealing, for fabricating large-scale reduced semiconducting oxide SERS substrates with high sensitivities. The SERS enhancement mainly stems from oxygen vacancy-associated electronic states created by the ion irradiation of sample; these states enhance the charge-transfer (CT) mechanism between the oxide substrate and the adsorbed molecules and thus significantly magnify SERS signals. The improved carrier mobility by vacuum annealing and the introduction of impurity energy levels and nanostructures enhances further the CT efficiency. A detection limit as low as 5 × 10-8 M was achieved; this is the highest sensitivity among the reported semiconductors, and it even compares to noble metals without the aid of "hot spots". The method is general-we demonstrate it on WO3, ZnO, and TiO2 substrates using Ar+ and N+ ion beam irradiation-and broadly applicable to produce noble-metal-free SERS substrates with high sensitivities.

Wafer-scale arrays of high-Q silica optical microcavities.

On-chip high-Q microcavities possess significant potential in terms of integration of optical microresonators into functional optoelectronic devices that could be used in various applications, including biosensors, photonic-integrated circuits, or quantum optics experiments. Yet, despite the convenience of fabricating wafer-scale integrated microresonators with moderate Q values using standard microfabrication techniques, surface-tension-induced microcavities (STIMs), which have atomic-level surface roughness enabling the observation of Q values larger than 106, could only be produced using individual thermal treatment of every single microresonator within the devised area. Here, we demonstrate a facile method for large-scale fabrication of silica STIMs of various morphologies. Q values exceeding 106 are readily obtained using this technique. This study represents a significant advancement toward fabrication of wafer-scale optoelectronic circuitries.

Ultrahigh-Responsivity Photodetectors from Perovskite Nanowire Arrays for Sequentially Tunable Spectral Measurement.

Compared with polycrystalline films, single-crystalline methylammonium lead halide (MAPbX3, X = halogen) perovskite nanowires (NWs) with well-defined structure possess superior optoelectronic properties for optoelectronic applications. However, most of the prepared perovskite NWs exhibit properties below expectations due to poor crystalline quality and rough surfaces. It also remains a challenge to achieve aligned growth of single-crystalline perovskite NWs for integrated device applications. Here, we report a facile fluid-guided antisolvent vapor-assisted crystallization (FGAVC) method for large-scale fabrication of high-quality single-crystalline MAPb(I1-xBrx)3 (x = 0, 0.1, 0.2, 0.3, 0.4) NW arrays. The resultant perovskite NWs showed smooth surfaces due to slow crystallization process and moisture-isolated growth environment. Significantly, photodetectors made from the NW arrays exhibited outstanding performance in respect of ultrahigh responsivity of 12 500 A W-1, broad linear dynamic rang (LDR) of 150 dB, and robust stability. The responsivity represents the best value ever reported for perovskite-based photodetectors. Moreover, the spectral response of the MAPb(I1-xBrx)3 NW arrays could be sequentially tuned by varying the content of x = 0-0.4. On the basis of this feature, the NW arrays were monolithically integrated to form a unique system for directly measuring light wavelength. Our work would open a new avenue for the fabrication of high-performance, integrated optoelectronic devices from the perovskite NW arrays.

Large-Scale Graphene on Hexagonal-BN Hall Elements: Prediction of Sensor Performance without Magnetic Field.

A graphene Hall element (GHE) is an optimal system for a magnetic sensor because of its perfect two-dimensional (2-D) structure, high carrier mobility, and widely tunable carrier concentration. Even though several proof-of-concept devices have been proposed, manufacturing them by mechanical exfoliation of 2-D material or electron-beam lithography is of limited feasibility. Here, we demonstrate a high quality GHE array having a graphene on hexagonal-BN (h-BN) heterostructure, fabricated by photolithography and large-area 2-D materials grown by chemical vapor deposition techniques. A superior performance of GHE was achieved with the help of a bottom h-BN layer, and showed a maximum current-normalized sensitivity of 1986 V/AT, a minimum magnetic resolution of 0.5 mG/Hz(0.5) at f = 300 Hz, and an effective dynamic range larger than 74 dB. Furthermore, on the basis of a thorough understanding of the shift of charge neutrality point depending on various parameters, an analytical model that predicts the magnetic sensor operation of a GHE from its transconductance data without magnetic field is proposed, simplifying the evaluation of each GHE design. These results demonstrate the feasibility of this highly performing graphene device using large-scale manufacturing-friendly fabrication methods.

Self-Powered, High-Speed and Visible-Near Infrared Response of MoO(3-x)/n-Si Heterojunction Photodetector with Enhanced Performance by Interfacial Engineering.

Photodetectors with a wide spectrum response are important components for sensing, imaging, and other optoelectronic applications. A molybdenum oxide (MoO(3-x))/Si heterojunction has been applied as solar cells with great success, but its potential in photodetectors has not been explored yet. Herein, a self-powered, high-speed heterojunction photodetector fabricated by coating an n-type Si hierarchical structure with an ultrathin hole-selective layer of molybdenum oxide (MoO(3-x)) is first investigated. Excellent and stable photoresponse performance is obtained by using a methyl group passivated interface. The heterojunction photodetector demonstrated high sensitivity to a wide spectrum from 300 to 1100 nm. The self-powered photodetector shows a high detectivity of (∼6.29 × 10(12) cmHz(1/2) W(-1)) and fast response time (1.0 μs). The excellent photodetecting performance is attributed to the enhanced interfacial barrier height and three-dimensional geometry of Si nanostructures, which is beneficial for efficient photocarrier collection and transportation. Finally, our devices show excellent long-term stability in air for 6 months with negligible performance degradation. The thermal evaporation method for large-scale fabrication of MoO(3-x)/n-Si photodetectors makes it suitable for self-powered, multispectral, and high-speed response photodetecting applications.

High-Throughput Universal DNA Curtain Arrays for Single-Molecule Fluorescence Imaging.

Single-molecule studies of protein-DNA interactions have shed critical insights into the molecular mechanisms of nearly every aspect of DNA metabolism. The development of DNA curtains-a method for organizing arrays of DNA molecules on a fluid lipid bilayer-has greatly facilitated these studies by increasing the number of reactions that can be observed in a single experiment. However, the utility of DNA curtains is limited by the challenges associated with depositing nanometer-scale lipid diffusion barriers onto quartz microscope slides. Here, we describe a UV lithography-based method for large-scale fabrication of chromium (Cr) features and organization of DNA molecules at these features for high-throughput single-molecule studies. We demonstrate this approach by assembling 792 independent DNA arrays (containing >900,000 DNA molecules) within a single microfluidic flowcell. As a first proof of principle, we track the diffusion of Mlh1-Mlh3-a heterodimeric complex that participates in DNA mismatch repair and meiotic recombination. To further highlight the utility of this approach, we demonstrate a two-lane flowcell that facilitates concurrent experiments on different DNA substrates. Our technique greatly reduces the challenges associated with assembling DNA curtains and paves the way for the rapid acquisition of large statistical data sets from individual single-molecule experiments.

Plasma-Induced Wafer-Scale Self-Assembly of Silver Nanoparticles and Application to Biochemical Sensing.

In this work, the wafer-scale silver nanoparticles fabricated by a self-assembly method was demonstrated based on a magnetron sputtering and plasma treatment process. Silver nanoparticles of different sizes and shapes were prepared, and the effects of the plasma treatment time, plasma gas composition, and power were systematically investigated to develop a method for low-cost and large-scale fabrication of silver nanoparticles. Furthermore, the surface-enhanced Raman scattering experiments: crystal violet, as the probe, was absorbed on the silver nanoparticles film of different size and density, and get the phenomena of surface-enhanced Raman scattering and surface-enhanced fluorescence. The results show that the proposed technique provides a rapid method for the fabrication of silver nanomaterial; the method is adaptable to large-scale production and is compatible with the fabrication of other materials and biosensors.

Scalable fabrication of nanostructured p-Si/n-ZnO heterojunctions by femtosecond-laser processing

We present a versatile, large-scale fabrication method for nanostructured semiconducting junctions. Silicon substrates were processed by femtosecond laser pulses in methanol and a quasi-ordered distribution of columnar nanospikes was formed on the surface of the substrates. A thin (80 nm) layer of ZnO was deposited on the laser-processed silicon surface by pulsed laser deposition, forming a nanostructured p-Si/n-ZnO heterojunction. We characterized the structural, optical, and electrical properties of the heterojunction. Electrical I–V measurements on the nanostructured p-Si/n-ZnO device show non-linear electric characteristics with a diode-like behavior. Electrical I–V measurements on a flat p-Si/n-ZnO reference sample show similar characteristics, however the forward current and rectification ratio are improved by orders of magnitude in the nanostructured device owing to its increased surface area. The fabrication method employed in this work can be extended to other homojunctions or heterojunctions for electronic and optoelectronic devices with large surface area.