Substrate Deposition Research Articles

High-sensitivity measurements of the nonlinear absorption coefficient of wide bandgap oxide thin films with the Z-scan method

The nonlinear response of wide bandgap oxide thin films gradually emerges and attracts attention with the development of an ultra-short and ultra-intense laser. In Z-scan technique, due to the extremely lower nonlinear response of thin film compared with the common substrate, it isn’t easy to measure the multiphoton absorption coefficient of wide bandgap oxide thin films. In this study, a method is proposed to suppress the substrate impact and improve the thin film measurement sensitivity. To make the thin film nonlinear intensity dominate the total intensity, including unwanted substrate impact, material and thickness of the substrate are analyzed. Considering the nonlinear effects of different substrates and the adhesion between the substrate and the thin film, 50 μm MgF2 and quartz glass are selected as the substrate for deposition. The nonlinear intensity of substrate is suppressed to at least 80% of the whole element or can even be ignored so that the normalized transmittance of the thin film can be obtained effectively. The two-photon and three-photon absorption coefficients of HfO2, Al2O3, and SiO2 thin film are measured at different wavelengths. The nonlinear absorption response measurements of wide bandgap oxide thin films can advance the design and fabrication of low-loss photonic devices in ultra-fast lasers.

Antimicrobial Food Packaging Based on Prodigiosin-Incorporated Double-Layered Bacterial Cellulose and Chitosan Composites.

Nowadays, food packaging systems have shifted from a passive to an active role in which the incorporation of antimicrobial compounds into biopolymers can promote a sustainable way to reduce food spoilage and its environmental impact. Accordingly, composite materials based on oxidized-bacterial cellulose (BC) and poly(vinyl alcohol)-chitosan (PVA-CH) nanofibers were produced by needleless electrospinning and functionalized with the bacterial pigment prodigiosin (PG). Two strategies were explored, in the first approach PG was incorporated in the electrospun PVA-CH layer, and TEMPO-oxidized BC was the substrate for nanofibers deposition (BC/PVA-CH_PG composite). In the second approach, TEMPO-oxidized BC was functionalized with PG, and afterward, the PVA-CH layer was electrospun (BC_PG/PVA-CH composite). The double-layer composites obtained were characterized and the nanofibrous layers displayed smooth fibers with average diameters of 139.63 ± 65.52 nm and 140.17 ± 57.04 nm, with and without pigment incorporation, respectively. FTIR-ATR analysis confirmed BC oxidation and revealed increased intensity at specific wavelengths, after pigment incorporation. Moreover, the moderate hydrophilic behavior, as well as the high porosity exhibited by each layer, remained mostly unaffected after PG incorporation. The composites’ mechanical performance and the water vapor transmission rate (WVTR) evaluation indicated the suitability of the materials for certain food packaging solutions, especially for fresh products. Additionally, the red color provided by the bacterial pigment PG on the external surface of a food packaging material is also a desirable effect, to attract the consumers’ attention, creating a multifunctional material. Furthermore, the antimicrobial activity was evaluated and, PVA-CH_PG, and BC_PG layers exhibited the highest antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa. Thus, the fabricated composites can be considered for application in active food packaging, owing to PG antimicrobial potential, to prevent foodborne pathogens (with PG incorporated into the inner layer of the food packaging material, BC/PVA-CH_PG composite), but also to prevent external contamination, by tackling the exterior of food packaging materials (with PG added to the outer layer, BC_PG/PVA-CH composite).

Aqueous solution deposition of indium hydroxide and indium oxide columnar type thin films

Abstract Crystalline In(OH)3 and UV-emitting In2O3 thin films with a unique columnar morphology have been successfully prepared for the first time via a simple aqueous solution deposition method. In the present study, sulfonate-terminated self-assembled monolayers on single-crystal Si wafers were used as substrates for the film deposition. Uniform In(OH)3 thin films formed on self-assembled monolayers in aqueous solutions of InCl3 · 4H2O at 60°C. These films, containing columnar In(OH)3 crystals, showed preferential growth orientation along the [100] direction. The current understanding of the film formation mechanism was discussed. After annealing in air at 400 °C, these films were converted to nanocrystalline In2O3 films without modification of the morphology. Photoluminescence emission from In2O3 films was reported at approximately 3.4 eV, which was ascribed to the near-band-edge emission.

Graphitic regulation of C/Cr composite film for 304 stainless steels bipolar plates

This work aims to deposit conductive and corrosion-resistant protective coatings for bipolar plates in proton exchange membrane fuel cells. The films' graphitization degree is regulated to obtain excellent conductivity and corrosion-resistance. A series of Cr-doped graphite-like carbon films with different substrate bias voltages and deposition times (600 V 2 h, 900 V, 2 h, 900 V, 3 h; and 1200 V, 2 h) were prepared on 304 stainless steels by plasma enhanced chemical vapour deposition method combined with magnetron sputtering technique. The results showed that an increase of substrate bias voltage increased substrate current density. The substrate current density was the highest when the substrate bias voltage was 1200 V at 400 °C. Subsequently high substrate bias voltage caused ID/IG to increase, indicating that the increase of energy contributes to graphitisation of the films. The particle size of the films decreased with increasing bias voltage, and the cross section showed that the prepared films were homogeneous and distinctive. The interface contact resistance (ICR) of the films at 1.4 MPa decreased with an increase of substrate bias voltage, showing that deeper graphitisation improves the conductivity of the films. The coated 304 stainless steels showed a considerable decrease in self-corrosion current density in comparison to the 304 stainless steel substrate. According to the VDI-3198 indentation test, the adhesion of the films and substrate belongs to the HF1 level. After long-term service, chromium oxides, iron oxides, and defects were formed on the surface, leading to an increase in ICR. The study revealed that the optimum technical parameters were 1200 V and 2 h.

Progress study on nickel ferrite alloy-graphene nanosheets nanocomposites as supercapacitor electrodes

Nickel ferrite (NiFe2O4) is a promising material for electrochemical supercapacitors among many metal ferrites. However, the low specific capacitance of NiFe2O4 limits its application. We present a new high-performance supercapacitor based on a nanocomposite material of NiFe alloy-graphene nanosheets (NiFe-A@GNS). We prepared NiFe2O4 nanoparticles using a simple liquid fusion method and used as a catalyst substrate for the chemical vapor deposition (CVD) synthesis of NiFe-A@GNS nanocomposite material. According to the XRD, TEM, SEM and Raman results, high-quality, crystalline, and graphitized GNS was successively composited with NiFe-A nanoparticles. Therefore, both pristine NiFe2O4 and the new composite material were evaluated as electrodes for supercapcitors. In the case of NiFe-A@GNS nanocomposite, we report a 3.2-fold increase in specific capacitance (845 F g − 1) when compared to the pristine NiFe2O4 (264 F g − 1). Furthermore, after 5000 cycles, the NiFe-A@GNS electrode retains 94.3% of its capacity, making it more stable than the NiFe2O4 electrode (62% after 2000 cycles). At 1.0 A g − 1 current density, the NiFe-A@GNS device has a high energy density (30.8 Wh kg−1) and a high power density (620 W kg−1). The synergistic effects of NiFe-A and graphene nanosheets, as well as the excellent surface characteristics, are the keys to the high performance of NiFe-A@GNS electrodes. Our design offers a promising method for developing high-performance supercapacitor devices.

Influence of substrate stress on in-plane and out-of-plane ferroelectric properties of PZT films

Solution-deposited ferroelectric films often are under mechanical stress due to the difference in thermal expansion coefficients between films and substrate materials. Knowledge of how stress changes the ferroelectric response under different actuation conditions is essential when selecting a substrate for film deposition. Here, a comparative study of the ferroelectric properties of lead zirconate titanate thin films on transparent fused silica glass and sapphire substrates is presented. Sapphire exerts a compressive in-plane stress on the film, favoring an out-of-plane domain orientation, while fused silica causes tensile in-plane stress and a predominantly in-plane domain configuration. As expected, the out-of-plane polarization is high under in-plane compressive stress but reduced by a factor of nearly 4 by in-plane tensile stress. In contrast, the in-plane polarization shows an unexpectedly weak stress dependence. It is larger by only about 10% under tensile stress compared to compressive stress. Permittivity increases when the major domain orientation does not coincide with the electric field. The observations are explained based on a model taking into account the crystallographic structure of the film.

Vapor deposition rate modifies anisotropic glassy structure of an anthracene-based organic semiconductor.

We control the anisotropic molecular packing of vapor-deposited glasses of ABH113, a deuterated anthracene derivative with promise for future organic light emitting diode materials, by changing the deposition rate and substrate temperature at which they are prepared. We find that at substrate temperatures from 0.65Tg to 0.92Tg, the deposition rate significantly modifies the orientational order in the vapor-deposited glasses as characterized by x-ray scattering and birefringence. Both measures of anisotropic order can be described by a single deposition rate-substrate temperature superposition (RTS). This supports the applicability of the surface equilibration mechanism and generalizes the RTS principle from previous model systems with liquid crystalline order to non-mesogenic organic semiconductors. We find that vapor-deposited glasses of ABH113 have significantly enhanced density and thermal stability compared to their counterparts prepared by liquid-cooling. For organic semiconductors, the results of this study provide an efficient guide for using the deposition rate to prepare stable glasses with controlled molecular packing.

Effects of Invasive Seaweed Depend on Underlying Physical Habitat Structure

Photo 1. A Green heron, Butorides virescens, forages on a mudflat covered with macroalgae. The dominant alga, Agarophyton vermiculophyllum, is visible as tufts of red-brown thalli and intermixed with Ulva spp., including Ulva lactuca. Photograph credit: Alice Besterman. Photo 2. Agarophyton vermiculophyllum forms mats up to 5 cm in depth above mudflat sediments, and generally between 2 and 3 cm deep. Here, a mat of Agarophyton has accumulated at the edge of a salt marsh, with some stems of Spartina alterniflora visible. The eastern mud snail, Tritia obsoleta (formerly Ilyanassa obsoleta), uses Agarophyton as refuge and substrate for egg-capsule deposition. Photograph credit: Alice Besterman. Photo 3. We used spotting scopes to observe shorebirds foraging across expansive mudflats exposed at low tide in the Virginia Coast Reserve LTER. We identified birds to the lowest taxonomic level, as well as the substrate they were used for foraging (bare mud, macroalgal mats, shallow water, oyster reefs, etc.). In this photograph, oyster (Crassostrea virginica) reef patches are visible in the foreground of the mudflat. Photograph credit: Alice Besterman. Photo 4. Hundreds of shorebirds including Limnodromus griseus (Short-billed dowitcher), Pluvialis squatarola (Black-bellied plover), and Calidris alpina (Dunlin) forage on a bare, topographically smooth mudflat in the Virginia Coast Reserve. Photograph credit: Alice Besterman. These photographs illustrate the article “Mudflat geomorphology determines invasive macroalgal effect on invertebrate prey and shorebird predators” by Alice F. Besterman and Michael L. Pace published in Ecology. https://doi.org/10.1002/ecy.3540.

Investigation of growth mode and surface roughness during homoepitaxial growth of silver metal using kinetic Monte Carlo simulation

In this work, a kinetic Monte Carlo (KMC) method for deposition is investigated to simulate the homoepitaxial growth of silver metal under experimental conditions. On-lattice and coarse-graining approximations are applied. KMC method is an ideal tool for simulating the Physical Vapor Deposition (PVD) process, which involves deposition and diffusion. The method accounts for surface diffusion processes, in addition to nearest-neighbor hopping and including Schwoebel-Ehrlich (SE). The SE mechanism effect on the growth mode and influences of substrate temperature and deposition rate on surface roughness have been studied in detail. The simulation results show when the Schwoebel hops are active, the growth mode is Frank-van der Merwe (2D). Furthermore, when the Schwoebel hops are not active, the growth mode is Volmer-Weber (3D). In addition, when increasing the deposition rate, the surface roughness increases due to the size of islands increase. Besides, when the temperature increases, the surface roughness decreases because the islands formed are transformed into a large cluster.

Formation and properties of mesoporous MoS-=SUB=-2-=/SUB=- films

Molybdenum disulfide is a crystalline material which attracts considerable attention due to explicit two-dimensional character of its electronic properties. To obtain MoS2 films thermally evaporated molybdenum and gaseous H2S were used as precursors in this work. As a result of chemical reaction of these precursors films consisting of flake-like of nanometer thickness assembled from parallel atomic layers with predominantly perpendicular (with respect to substrate surface) orientation were deposited on the surface of Si substrate. In this work we investigate the dependence of film morphology on deposition time, substrate temperature and concentration of precursors in gaseous phase. Presence of mono- and bi-layered structures in the film was revealed using Raman spectroscopy and electron microscopy. Dependence of photoluminescence properties on size of crystallites in produced films was also studied. Keywords: 2D materials, transition metal dichalcogenides, flakes, monolayers, mesoporous films.

Influence of the Deposition Process and Substrate on Microstructure, Phase Composition, and Residual Stress State on As-Deposited Cr-Al-C Coatings

Influence of the Deposition Process and Substrate on Microstructure, Phase Composition, and Residual Stress State on As-Deposited Cr-Al-C Coatings

Thermal barrier coatings for high-temperature application on superalloy substrates - A review

On account of protecting the metal components which are subjected to high temperatures like power plant's turbine blades and internal combustion engines, the thermal barrier coating is indispensable. The coating provides effective thermal insulation to the components and permits higher operating temperature, increasing the component's life by reducing oxidation, thermal fatigue, and increasing the durability of the substrate. Different coating techniques like Plasma spray, Electron-beam physical vapor deposition, bond coat, topcoat materials, and superalloy substrate materials were investigated.This paper reviewed researches on thermal barrier coating techniques, recent findings of coating materials, property difference at high-temperature performance, and failure mechanism and the findings of this review can be adopted for future researches.

Model-free analysis of molecular orientation in amorphous organic semiconductor films for understanding its formation dynamics: Methods and systematic investigation

To achieve high-performance organic light-emitting diodes (OLEDs), various amorphous organic semiconductor materials were developed, and the higher-order structure of their films and their formation dynamics were investigated. In particular, their molecular orientations were widely analyzed because it significantly affects optical and electrical properties of the OLEDs. However, conventional methods of the analysis of the orientation order parameter ( S ) need the construction of an anisotropic optical model, which brings a certain degree of analytical error and thus makes it difficult to assess the slight changes in S values arising from differences in experimental conditions. In this study, we present a simple model-free analytical method to estimate S values, named "QACIOS", that avoids the significant analytical errors and applies to various OLED materials, including materials that easily crystallize. In applying the method to UV/visible and IR spectral regions, the S values of electronic and vibrational transition dipole moments in the films can be simply estimated. The orientations of functional groups in single-layer and multilayer samples are obtainable separately, and in situ measurements are also demonstrated. Furthermore, we present a systematic analysis of the dependence of S on experimental conditions during sample fabrication such as deposition rate, substrate temperature, and substrate surface. From this analysis, the difference in formation dynamics of the molecular orientation of two structural isomers of OLED materials is quantitatively clarified, further demonstrating the usefulness of the method. A model-free simple analytical method by quantitative absorbance comparison with an isotropically oriented standard (QACIOS) is applied to systematic investigation of orientations of long molecular axis and functional groups in amorphous organic semiconductor films and their formation dynamics. • A model-free simple analytical method for reliable estimation of orientation order parameter is proposed and applied to many kinds of amorphous OLED materials. • Orientation analysis of functional groups in single-layer and multilayer samples are performed. • The difference in formation dynamics of molecular orientation of two OLED isomers is clarified quantitatively. • The method can be a commonly-used standard method for orientation analysis of OLED films.

Effect of growth parameters on defect structure and optical properties of ultrathin SnO2 films

Tin oxide films with thicknesses in the range from 5 to 110 nm have been deposited by reactive dc magnetron sputtering of Sn in Ar + O plasma at a low working pressure of 1.0× 10 −3 Torr on glass substrates at different temperatures (150–400 °C). The effect of deposition time, substrate temperature, and oxygen partial pressure on surface morphology , crystallographic structure, optical properties, and photoluminescence characteristics of SnO 2 films has been studied and correlated with their defect structure . The structural transformation from nanocrystalline to polycrystalline of thicker films >40 nm and films were grown at higher temperature is explained based on adatom mobility and uniform substrate coverage. Based on photoluminescence characteristics and transmittance spectra, the 20 nm thick film exhibits the least defect structure and best electronic and optical behaviors. • Ultrathin SnO 2 films (5–20 nm) are successfully grown by DC reactive sputtering. • Effect of scaling down film thickness (down to 5 nm) on physical properties. • Correlation between defect structure and optical properties. • Thinner films are much smoother than the thicker films. • Low structural defect concentration found in 10–40 nm films.

An anodeless, mechanically flexible and energy/power dense sodium battery prototype

An enabling anode-less sodium metal battery design was proposed by encapsulating various zinc-containing multialloys (from ternary to medium/high entropy alloys) within the interweaved carbon nanotubes as the lightweight, mechanical-flexible Na deposition substrates.

Designing Zinc Deposition Substrate with Fully Preferred Orientation to Elude the Interfacial Inhomogeneous Dendrite Growth.

The development of zinc-ion batteries with high energy density remains a great challenge due to the uncontrollable dendrite growth on their zinc metal anodes. Film anodes plated on the substrate have attracted increasing attention to alleviate these dendrite issues. Herein, we first point out that both the random crystal orientation and the low metal affinity of the substrate are important factors of zinc dendrite formation. Accordingly, the (1 0 1) fully preferred tin interface layer with high zinc affinity was fabricated by chemical tin plating on (1 0 0) oriented copper. This tin decorated copper substrate can realize high reversible zinc plating/stripping behavior, and full cell using this zinc plated substrate can be operated for more than 1000 cycles with high capacity retention (85.3%) and low electrochemical impedance. The proposed strategy can be also applied to lithium metal batteries, which demonstrates that the substrate orientation regulation and metal affinity design are the promising approaches to achieve dendrite-free metal anode and overcome the challenges of highly reactive metal anodes.

Effect of processing technology on structural stability of SiC/SiBCZr ceramic matrix composites

SiC/SiBCZr composites were prepared through polymer impregnation and pyrolysis process using the second generation SiC fibers as raw material. The effects of surface substrate removal, secondary densification, and deposition coating on the structure, mechanical properties, and high temperature stability of SiC/SiBCZr composites were investigated. Results showed that the porosity of SiC/SiC composites could be greatly diminished by the optimized treatment process, and the surface of SiC/SiBCZr composites is uniformly filled into the pores by β-SiC particles, thereby achieving the sealing effect. Meanwhile, the as-prepared SiC/SiBCZr composites had excellent high temperature structural stability. At the later stage of oxidation reaction, borosilicate oxidation products with moderate fluidity, fluid lava form and self repairing function generated from ceramic matrix can effectively inhibit the oxidation reaction and improve the high temperature structural stability of SiC/SiBCZr composites. The above-mentioned high temperature structural stability provided the foundation and technical support for improving the service life and expanding the application of SiC/SiBCZr composites.

Nanoindentation of Chromium Oxide Possessing Superior Hardness among Atomic-Layer-Deposited Oxides.

Chromium (III) oxide is a technologically interesting material with attractive chemical, catalytic, magnetic and mechanical properties. It can be produced by different chemical and physical methods, for instance, by metal–organic chemical vapor deposition, thermal decomposition of chromium nitrate Cr(NO3)3 or ammonium dichromate (NH4)2Cr2O7, magnetron sputtering and atomic layer deposition. The latter method was used in the current work to deposit Cr2O3 thin films with thicknesses from 28 to 400 nm at deposition temperatures from 330 to 465 °C. The phase composition, crystallite size, hardness and modulus of elasticity were measured. The deposited Cr2O3 thin films had different structures from X-ray amorphous to crystalline α-Cr2O3 (eskolaite) structures. The averaged hardness of the films on SiO2 glass substrate varied from 12 to 22 GPa and the moduli were in the range of 76–180 GPa, as determined by nanoindentation. Lower values included some influence from a softer deposition substrate. The results indicate that Cr2O3 could be a promising material as a mechanically protective thin film applicable, for instance, in micro-electromechanical devices.

Anatomy and dynamics of a mixed contourite sand sheet, Ryukyu Island Arc, northwestern Pacific Ocean

Contourites are well-known from many continental margins under the influence of bottom currents but have been little reported from the Pacific Ocean. This paper documents a new area of contourite-controlled sedimentation in the NW Pacific Ocean, which we call the Ryukyu Sand Sheet. This contourite sand sheet has an area of around 35,000 km2 and extends from the narrow island shelves to over 1500 m water depth. It comprises mainly moderate to well-sorted fine-grained sands, with current ripples and giant sediment waves and is also associated with small drifts. It is formed under the influence of three principal current systems – the Kuroshio Current, the Kuroshio Countercurrent and the Ryukyu Current. The interaction of these currents with each other and with a complex seafloor topography, spawns a series of meso-scale gyres, eddies and vortices that shape the seafloor and lead to deposition of an extensive sandy substrate, locally with gravels and exposed seafloor. Strong surface currents, as well as deep-water thermohaline circulation, both influence the depositional and erosional processes of deep-sea sediments. The role of the modern Kuroshio Current in this context supports earlier work that proposed an ancestral Kuroshio Current for the deposition of Miocene contourites onshore Japan. Sediment supply to the Ryukyu Sand Sheet is by a mixed process of seafloor polishing and sand spillover that involves combined oceanographic and gravitational processes.

Novel degradation of amoxicillin by WO3/Ag3VO4 Z-scheme heterojunction deposited on rGO

In this work, Ag3VO4 was successfully hybridized with WO3 to form Ag3VO4/WO3 (AW) Z scheme heterojunction. Then, rGO was used as a substrate for deposition of the synthesized AW to further improve its electron-hole separation efficiency and surface area. The synthesized AW deposited on rGO (AW/rGO) was used for degradation residual amoxicillin upon visible light excitation. The synthesized samples were deeply characterized by XRD, HR-TEM, BET, UV–Vis, PL and Mott–Schottky plots. Scavenger experiments were also conducted to investigate photocatalytic mechanism. The obtained results indicated well hybridizing and matching band potentials between Ag3VO4 and WO3. Thus, the photo-excited electrons (e−) at WO3 conduction band (CB) would be transported from boundary to Ag3VO4 valence band (VB) and combined with its holes (h+) to inhibit charge recombination in each material resulting in accumulation of huge amounts of available e− at Ag3VO4 CB and h+ in WO3 VB. The generated e− and h+, which were high redox potentials, effectively participated in degradation of amoxicillin. The used rGO effectively increased surface area for amoxicillin adsorption and electron transfer for charge separation of the AW. Thus, the synthesized AW/rGO sample exhibited novel amoxicillin photocatalytic degradation. Finally, the regenerating experiment results indicated novel recycling ability of the AW/rGO photocatalyst.