Substrate Position Research Articles

(Cr1-xAlx)N Coating Deposition by Short-Pulse High-Power Dual Magnetron Sputtering.

The paper deals with the (Cr1-xAlx)N coating containing 17 to 54 % Al which is deposited on AISI 430 stainless steel stationary substrates by short-pulse high-power dual magnetron sputtering of Al and Cr targets. The Al/Cr ratio in the coating depends on the substrate position relative to magnetrons. It is shown that the higher Al content in the (Cr1-xAlx)N coating improves its hardness from 17 to 28 GPa. Regardless of the Al content, the (Cr1-xAlx)N coating manifests a low wear rate, namely (4.1-7.8) × 10-9 and (3.9-5.3) × 10-7 mm3N-1m-1 in using metallic (100Cr6) and ceramic (Al2O3) counter bodies, respectively. In addition, this coating possesses the friction coefficient 0.4-0.7 and adhesive strength quality HF1 and HF2 indicating good interfacial adhesion according to the Daimler-Benz Rockwell-C adhesion test.

Structural and piezoelectric properties of AlN thin films grown by pressure gradient sputtering

Aluminum nitride (AlN) thin films were grown by pressure gradient sputtering (PGS) and conventional sputtering methods. A pressure gradient with low pressure at a substrate position was measured only in the PGS method. AlN films highly oriented along the c-axis were grown by both methods, but there were remarkable differences in the surface roughness and the piezoelectric properties. The average surface roughness (Ra) obtained by atomic force microscopy images was much smaller in the AlN grown by the PGS method. The piezoelectric constant (d 33) of the AlN grown by the PGS method was higher than that of the conventional method. These results revealed that the PGS technique has an advantage in the growth of AlN films that are highly c-axis oriented with a single dielectric domain.

Magnetron Deposition of Cr Coatings with RF-ICP Assistance

The article describes a comparative analysis of chromium coatings deposited by magnetron sputtering with and without ion assistance induced by a radiofrequency inductively coupled plasma (RF-ICP) source. Four series of 2 µm-thick Cr coatings were prepared, and then their cross-sectional microstructure, crystal structure and corrosion resistance were investigated by scanning and transmission electron microscopy, X-ray diffraction and a potentiodynamic polarization method. RF-ICP assistance led to significant enhancement (almost twofold) of ion current density in a substrate. The role of RF-ICP assistance in coating properties for planetary-rotated substrates was defined in terms of ion-to-atom ratio in particle flux entering a substrate. Calculations of particle and ion flux densities revealed an increase in ion-to-atom ratio from 0.18 to 1.43 and 0.11 to 0.84 in substrate positions distant from the magnetron sputtering systems depending on their design. RF-ICP assistance is beneficial for depositing dense Cr coatings with increased corrosion resistance in a 3.5 wt.% NaCl solution. The corrosion rate of AISI 321 steel can be decreased from 6.2 × 10−6 to 4.0 × 10−8 mm/year by deposition of the dense Cr coating.

Manipulation of Anode Nanostructure and Composition By Glancing Angle Deposition for Thin-Film Solid Oxide Fuel Cells

Co-sputtering is a simple yet effective technique for fabricating a thin film of composite materials and different compositions by adjusting the electrical power of each sputtering target. However, practical issues arise when depositing cermet materials such as Ni-YSZ and Ni-GDC because of the contrasting characteristics of metal and ceramic sputtering targets. For example, the surface binding energy of GDC is significantly higher than that of Ni, resulting in a considerably lower sputtering yield of GDC. The difference in sputtering yield is further exacerbated by the low power density limit of the GDC target, which is set by its unfavorable material properties such as brittleness and low thermal conductivity. In contrast, due to its magnetic property, Ni requires sufficiently high sputtering power during magnetron sputtering.This work combines co-sputtering with advanced sputtering techniques such as glancing angle deposition (GLAD) and oblique angle deposition (OAD) to fabricate otherwise unobtainable Ni-GDC anode microstructure with various compositions. Reduced flux capture area of Ni caused by the high incident angle of GLAD allowed control of thin-film compositions, and optimal composition was determined based on fuel cell performance and electrochemical impedance spectroscopy (EIS) analysis. A sufficient amount of GDC was necessary to expand the triple-phase boundary (TPB) and suppress the thermal agglomeration of highly mobile Ni.The effect of electrode nanostructure on fuel cell performance was also investigated. The ballistic shadowing effect during OAD was utilized to produce thin-film electrodes with various porosities. With the increase of the deposition angle, the porosity increased, whereas the in-plane electrical conductivity decreased due to the reduced density. The columnar structure was also manipulated by managing the substrate position through azimuthal rotation. As a result, various columnar structures such as vertical posts, slanted posts, and zig-zag were fabricated, and the optimal microstructure was determined via electrochemical examinations.

Deposition of PbS thin films using a continuous flow reactor: Comparison of the modified technique with conventional methods in the coating of PbS thin film on the substrate

A reactor was designed to coat the PbS thin film on glass substrate by continuous flow. A methodology is proposed to deposit PbS films based on reducing the roughness via a laminar and continuous flow in the reactor without being affected by the chaotic properties of the turbulent flow. The modified coating method was named flow-through chemical deposition (FTCD). The morphological analysis demonstrated that the surface roughness of PbS films deposited by the FTCD method was lower than the other films. The wetting behaviour of PbS surfaces is consistent with the roughness of the PbS layers coated on the substrate. The results revealed that the properties of the films were influenced from the deposition method, the substrate position and the movement of the chemical solution in the reaction medium. The developed innovative approach has shown promising results for the chemical synthesis of PbS films in the context of surface modification.

Copper(II)-Doped Two-Dimensional Titanium-Based Metal-Organic Frameworks toward Light-Driven CO2 Reduction to Value-Added Products.

Recently, metal-organic framework (MOF)-based photocatalysts for an efficient CO2 reduction reaction have drawn wide attention in multidisciplinary fields and sustainable chemistry. In this work, a series of Cu2+-doped two-dimensional Ti-based MOFs were fabricated by a facile in situ solvothermal method. Cu2+ ions were doped in equal proportions and uniformly dispersed in the crystal structure of the MOF matrix. Interestingly, the doping content of Cu2+ ions and the photocatalytic performance displayed an obvious volcanic relationship, the medium-concentration Cu2+-doped sample (T1-2Cu) held the greatest activity with 100% carbonaceous product (CH4 and CO) formation, and the CH4 production rate was 3.7 μmol g-1 h-1 with 93% electron selectivity. The band structure, local electronic structure, carrier separation kinetics, and CO2 adsorption studies demonstrated that the excellent photocatalytic activity of T1-2Cu benefited from the appropriate amount of Cu2+ ion doping: (1) a doping amount of 2 atom % optimized the conduction band position of the MOF substrate and endowed T1-2Cu with strong reduction potential in thermodynamics, (2) doping Cu2+ ions tuned the local electronic environment around titanium oxide clusters and optimized the generation, separation, and migration processes of photoinduced carriers, and (3) the introduction of Cu2+ ions also provided more accessible active sites and more probabilities for the adsorption and activation of CO2 reactants.

Multi-layer growth of tungsten disulphide using thermal chemical vapour deposition

Transition metal dichalcogenides, in their 2D form are proven to be significant material for next-generation nanoelectronic and optoelectronic devices. However, for the realization of practical applications, it is very important to devise facile, and cost-effective synthesis routes without compromising their quality. In this work, multi-layer 2D tungsten disulphide (WS2) has been synthesized using thermal assisted chemical vapour deposition technique. The synthesis was carried out using two different substrates, and the effect of relative position of tungsten trioxide powder and substrate on the multi-layer growth of WS2 has been studied. The nucleation density and layer number is observed to be varying with the reaction time and the type of the substrate. The as-synthesized samples were characterized by using field emission scanning electron microscopy, and Raman spectroscopy.

A Chemical Vapor Deposition Diamond Reactor for Controlled Thin‐Film Growth with Sharp Layer Interfaces

A microwave plasma reactor for diamond growth that allows for highly controllable process conditions is presented. The position of the diamond substrate within the reactor can be accurately controlled. Thus, equilibration of plasma conditions can be carried out after changes in process parameters. With this approach, sharp layer transitions among doped, undoped, and isotopically controlled diamond films can be obtained. In addition to the sample transfer, the growth temperature is maintained through a substrate heater, and a clean reactor environment is realized by a load‐lock sample exchange system. The plasma conditions are constantly monitored by optical emission spectroscopy. Using this system, the growth of nanoscopic sandwich structures is demonstrated with controlled isotopic ratios down to ≈10 nm thickness and N(V) layers below 50 nm are obtained on (001)‐oriented diamond. Growth rates and doping efficiencies depending on the used methane concentration are presented. Characterization with continuous‐wave optically detected magnetic resonance yields an average contrast of 4.1% per nitrogen vacancy (NV) orientation in layers with a thickness below 100 nm. Depending on the used methane concentration, surface morphology and NV doping homogeneity are influenced as observed by photoluminescence and atomic force microscopy measurements.

Differential analysis of the influence mechanism of ultrasonic vibrations on laser cladding

Although the laser cladding technology is widely used in various fields, the laser cladding layer is prone to pores, inclusions and microcracks, severely limiting the popularization and application of this technology. High-frequency mechanical vibration can effectively reduce the micro defects in the cladding layer and strengthen the solidification structure of the cladding layer. In this paper, a laser cladding system for a disc laser assisted by ultrasonic vibration is built, and the dynamic response of ultrasonic vibration of the cladding experiment platform is tested. A finite element model of the dynamic response of the cladding experiment platform under ultrasonic vibration was established, and the difference of the vibration of the experimental platform substrate at different positions under the ultrasonic vibration was calculated. The internal amplitude of the substrate is differentiated in a hemispherical shape with the vibration source as the center and is distributed under the influence of ultrasonic vibration. On this basis, the phase field method was used to establish the ultrasonic-assisted disc laser cladding solidification model to obtain the dendrite growth state during the solidification process. The calculation reveals the change law of single crystal and polycrystalline solidification growth under the influence of ultrasonic amplitude at different substrate positions. Calculations show that ultrasonic vibration can effectively increase the growth rate of dendrites and promote the formation of secondary dendrite arms. The polycrystalline solidification growth model is closer to reality. The competitive growth of dendrites suppresses the growth of primary dendrites to a certain extent and affects the selective growth of dendrites. The results show that the larger the ultrasonic amplitude, the more rapid the formation of secondary dendrite arms.

Plasma diagnostics and film growth of multicomponent nitride thin films with magnetic-field-assisted-dc magnetron sputtering

During direct current magnetron sputtering (dcMS) of thin films, the ion energy and flux are complex parameters that influence thin film growth and can be exploited to tailor their properties. The ion energy is generally controlled by the bias voltage applied at the substrate. The ion flux density however is controlled by more complex mechanisms.In this study, we look into magnetic-field-assisted dcMs, where a magnetic field applied in the deposition chamber by use of a solenoid coil at the substrate position, influences the energetic bombardment by Ar ions during deposition. Using this technique, CrFeCoNi multicomponent nitride thin films were grown on Si(100) substrates by varying the bias voltage and magnetic field systematically. Plasma diagnostics were performed by a Langmuir wire probe and a flat probe. On interpreting the data from the current-voltage curves it was confirmed that the ion flux at the substrate increased with increasing coil magnetic field with ion energies corresponding to the applied bias. The increased ion flux assisted by the magnetic field produced by the solenoid coil aids in the stabilization of NaCl B1 crystal structure without introducing Ar ion implantation.

Ultra-Flexible Organic Electronics for Biomedical Application

Since biometric sensing using light can noninvasively measure biological information from the outside of the body, various information can be obtained from dynamic things such as blood oxygen concentration and heart rate to static things such as fingerprints and veins. Among them, a flexible organic imager can be attracted to the body, so it is used as wearable electronics. Utilizing its flexibility, imagers capable of imaging fingerprints and veins, pulses that can be directly applied to the skin, blood oximeters, muscle contraction sensors, etc. have been reported.In this study, we have developed ultra-flexible and lightweight highly efficient, ultra-flexible, air-stable, three-color, polymer light-emitting diodes (PLEDs) The total thickness of the devices, including the substrate and encapsulation layer, is only three micrometers, which is one order of magnitude thinner than the epidermal layer of the human skin. Due to the very thin substrate and neutral position, our device shows the highly flexibility and conformability. The PLEDs are directly laminated on the surface of skin and are used as indicators/displays. And also, we have developed a sheet-type image sensor that enables high-resolution and high-speed reading. Our conformable imager has pixel pitches as small as 50 µm, with resolutions of up to 508 dpi. Using our conformable imager, we succeed to take a high-resolution image of fingerprints and veins used for biometric authentication.

Tailoring the structural and optical properties of HiPIMS TiO2 thin films for photovoltaic applications

Titanium dioxide (TiO2) thin films are deposited onto glass and silicon <100> substrates by high power impulse magnetron sputtering (HiPIMS) at various substrate positions from the substrate-holder center (x = 0, 10, 20 and 30 mm). The structural analysis conducted through XRD and Raman spectroscopy shows that all the films deposited at lower radial distance (x = 0–20 mm) are identified as pure anatase phase of TiO2, while those deposited at 30 mm contain a small trace of rutile phase with anatase phase remaining dominant. AFM analysis reveals homogenous surfaces with low values of roughness (2.6–3.8 nm) and a decrease of grain size with the substrate position. The films exhibit high refractive index and large indirect optical band gaps (3.25–3.38 eV). Finally, UV-blocking and antireflection characteristics are studied.

Programming Directed Motion with DNA-Grafted Particles.

Colloidal particles can be programmed to interact in complex ways by functionalizing them with DNA oligonucleotides. Adding DNA strand-displacement reactions to the system allows these interparticle interactions to respond to specific changes in temperature. We present the requirements for thermally driven directed motion of colloidal particles, and we explore how these conditions can be realized experimentally using strand-displacement reactions. To evaluate the concept, we build and test a colloidal "dancer": a single particle that can be driven to move through a programmed sequence of steps along a one-dimensional track composed of other particles. The results of these tests reveal the capabilities and limitations of using DNA-mediated interactions for applications in dynamic systems. Specifically, we discuss how to design the substrate to limit complexity while permitting full control of the motile component, how to ratchet the interactions to move over many substrate positions with a limited regime of control parameters, and how to use technological developments to reduce the probability of detachment without sacrificing speed.

A Computational Alanine Scanning of Heptapeptide RRRSAGM Targeting Dengue NS2B/NS3 Protease

The pathogenic dengue virus (DV) transmitted mainly by the Aedes aegypti mosquito has been the most rapidly spreading mosquito-borne viral disease and became a serious threat to global health issue in tropical and sub-tropical countries. The clinical symptoms ranging from mild to a fatal dengue hemorrhagic fever and dengue shock syndrome, characterized by failure of the circulation system that may lead to death. There are still no drugs or vaccines available in the market to prevent or treat dengue infections. Hence, the development of successful drugs that are safe and offer a long-lasting protection against dengue viruses is needed. Recently, the discovery of peptides with high specificity, selectivity, and efficacy; and relatively safer than small-molecule drugs have become a promising agent for a new drug. Previously, a molecular dynamic simulation reported that peptide NRRRRSAGMI from the capsid’s cleavage region had the most hydrogen bonds with NS2B/NS3 protease, thus it leads into a starting linear heptapeptide R(P3)-R(P2)-R(P1)-S(P1’)-A(P2’)-G(P3’)-M(P4’). This study aimed to investigate the importance and specificity of individual amino acid residue of the heptapeptide substrate on the binding affinity and interaction to NS2B/NS3 dengue protease through computational alanine scanning. It showed that the changing of P1 and P2 arginine to alanine resulted to higher values of binding affinity. Thus, the arginine is an important residue at the P1 and P2 positions for the binding of the substrate peptide to DENV NS2B/NS3 protease, hence the amino acid residues which are essential for the enzyme-substrate interactions can be predicted through computational alanine scanning.&#x0D; HIGHLIGHTS&#x0D; &#x0D; Dengue is a mosquito-transmitted virus cause of arthropod-borne viral disease&#x0D; The discovery of peptides became a potential agent for dengue virus and previously peptide NRRRRSAGMI has been reported as starting linear heptapeptide RRRSAGM&#x0D; A computational alanine scanning based on the peptide RRRSAGM has been performed&#x0D; S1 and S2 pockets show strong preferences for basic amino acids, whereas the S3 pocket is less selective for basic residue&#x0D; The arginine at P1 and P2 positions of the heptapeptide substrate contribute significantly to the substrate binding affinity&#x0D; &#x0D; GRAPHICAL ABSTRACT

Ion energy analysis of a bipolar HiPIMS discharge using a retarding field energy analyser

The time evolution of the positive ion energy distribution functions (IEDF’s) at the substrate position in an asymmetric bipolar high-power impulse magnetron sputtering (HiPIMS) system was determined using a gridded energy analyser. This was done for a range of operating conditions, namely the positive voltage U rev and ‘on-time’ negative pulse duration τ neg. The magnetron sputtering discharge was equipped with a Nb target. Based on the knowledge of the IEDF’s, the bombarding ion flux density Γi and energy flux density Q i to a grounded surface were calculated. Time-resolved IEDF measurements showed that ions with energies approaching the equivalent of the positive pulse voltage U rev were generated as the reverse positive voltage phase developed. On time-average, we observed that increasing the set U rev value (from 0 to 100 V), resulted in a marginal decrease in the ion flux density Γi to the analyser. However, this is accompanied by a five-fold increase in the ion energy flux density Q i compared to the unipolar, U rev = 0 V case. Reducing the negative HiPIMS pulse duration τ neg (from 130 to 40 μs) at a constant discharge power leads to a modest increase in Γi, but a four-fold increase in Q i. The results reveal the benefit of the bipolar HiPIMS technique, in which it is possible to control and enhance the power density of ions bombarding a grounded (or fixed bias) substrate, for potentially better tailoring of thin film properties.

Production of 4-Ethyl Malate through Position-Specific Hydrolysis of Photobacterium lipolyticum M37 Lipase.

Microbial lipases are used widely in the synthesis of various compounds due to their substrate specificity and position specificity. 4-Ethyl malate (4-EM) made from diethyl malate (DEM) is an important starting material used to make argon fluoride (ArF) photoresist. We tested several microbial lipases and found that Photobacterium lipolyticum M37 lipase position-specifically hydrolyzed DEM to produce 4-EM. We purified the reaction product through silica gel chromatography and confirmed that it was 4-EM through nuclear magnetic resonance analysis. To mass-produce 4-EM, DEM hydrolysis reaction was performed using an enzyme reactor system that could automatically control the temperature and pH. Effects of temperature and pH on the reaction process were investigated. As a result, 50°C and pH 4.0 were confirmed as optimal reaction conditions, meaning that M37 was specifically an acid lipase. When the substrate concentration was increased to 6% corresponding to 0.32 M, the reaction yield reached almost 100%. When the substrate concentration was further increased to 12%, the reaction yield was 81%. This enzyme reactor system and position-specific M37 lipase can be used to mass-produce 4-EM, which is required to synthesize ArF photoresist.

Seasonal patterns of microhabitat selection in the Southern Iberian spined-loach Cobitis paludica

The Southern Iberian spined-loach Cobitis paludica is an Iberian endemism threatened by human activities, including habitat destruction. For this reason, the development of conservation and the recovery plans for the species calls for a precise knowledge of its habitat requirements. Here, microhabitat use and selection patterns were investigated to determine the limiting factors for the species in different seasons, corresponding to a gradient in flow conditions. The microhabitat of the loach was analysed in the River Jarama (Tagus River basin, central Spain) in the period of maximum activity between March and September 2013. No significant differences in microhabitat use were found between males and females, and only very weak ontogenetic changes were detected. The microhabitat used by the loach varied significantly throughout the study period, generally adapting to the flow-mediated dynamics of available habitat. The most stable pattern throughout the year was the use of very low water velocities. Additionally, the loach made selective use of certain microhabitat features, with slight adjustments to the seasonally changing habitat conditions. The loach significantly selected positions with abundant silt substrate and aquatic vegetation, and avoided coarser substrates. The availability of fine substrates and abundant vegetation is therefore a critical habitat requirement for the loach, which needs instream structures that provide foraging substrate, refuge and safe positions for spawning. Selection of refuge elements (deep habitats, aquatic vegetation) was especially apparent under low-flow conditions. Human activities leading to the loss of these critical microhabitats may threaten the survival of already scarce loach populations.

Optimization of Growth Parameters of Thermal Chemical Vapor Deposition Method for 2D MoS2 Synthesis

Even after a decade of research on MoS2, it is still quite challenging to obtain high quality MoS2 films using a controlled synthesis technique. Out of all the available methods chemical vapor deposition (CVD) has proven to be a reliable technique to produce MoS2 thin films. The CVD growth process is sensitive to variety of parameters involved in the process. In the present work, we report the effect of pressure, temperature, gas flow, and position of substrate on the growth of MoS2 films. After several failures, the technique is optimized to synthesize high quality MoS2 films on quartz substrate. Further, the films are characterized using XRD, UV-Vis Spectroscopy, Photoluminescence Spectroscopy and Raman Spectroscopy. The main objective of this work is to formulate a method that produces MoS2 films using thermal CVD process by optimizing various parameters.

Growth of Al-doped ZnO nanostructures in low pressure background gas by pulsed laser deposition

In this work, the deposition of nanostructures by room temperature pulsed laser deposition (PLD) in low pressure (2.6 Pa) O2, N2, He, and Ar at different substrate positions are studied. The substrates are placed at the normal on-axis/center position; and off-axis i.e. 4.5 cm above and below the center position. Optical emission spectra and ion velocity are measured by using spectrometer and ion probe. The overall intensity of optical emission is in the order of Ar > O2/N2 > He while the ion velocity is in the reverse order. The inverse relation of optical emission and ion velocity suggest that collisions of the ablated specie possibly result in strong emission and impede the ion velocity at the same time. Amorphous films are obtained for the substrates placed at on-axis/center in all the background gases and at the bottom position for O2. However, crystalline ZnO and Zn nanostructures are deposited at the bottom position in N2, He, and Ar. Larger structures are deposited in Ar and the presence of nanorods are detected by TEM. The results further suggest that in N2, He or Ar, the ablated plasma plume is spatially and thermally confined; governed by the properties of the gas. Nucleation of nanostructures occurred in the plasma plume even at low background pressure and deposited on the substrates that are placed at the bottom position. Between the two inert gases, Ar with higher atomic mass and lower thermal conductivity results in high collisions and thermal confinement that leads to some large structure as compared to those obtained in He. In addition, in the presence of N2, He or Ar, Zn crystallites are also detected, which can act as catalyst for nanostructure formation.

Coastal Wetland Surface Elevation Change Is Dynamically Related to Accommodation Space and Influenced by Sedimentation and Sea-Level Rise Over Decadal Timescales

The fate of mangroves and saltmarshes under conditions of accelerating sea-level rise is dependent upon sedimentation and surface elevation gain that is sufficient to maintain substrate positions within a shifting tidal frame. This study focuses on coastal wetlands fringing Westernport Bay, a large tidal embayment of southeastern Australia where mangroves occupy lower tidal positions than saltmarshes. Estimates of vertical accretion, surface elevation change, and autocompaction derived from a 20-year record of observations were integrated with estimates of sedimentation at the decadal to century time-scale derived from 210Pb chronology to model the relationship between surface elevation gain and accommodation space at timescales relevant to management and decision-making. This model was validated against records of shoreline changes extracted from time-series aerial photography. Sedimentation and surface elevation gain vary spatially on the basis of available accommodation space and sediment supply, which are influenced by hydrodynamic conditions within the bay. Since sea-level rise increases available accommodation space, these relationships provided the means to project the outcome of accelerating sea-level rise on equilibrium accommodation space of mangroves and saltmarshes. Sea-level rise will generally deepen substrate positions within the tidal frame, creating conditions favorable for mangrove forests. Where sediment supply is high, maintenance (and some progradation) of mangrove shorelines may occur under projected low rates of sea-level rise; these conditions are limited to shorelines near sedimentary basins and where there is considerable lateral accommodation space. The same fate is not likely under a high sea-level rise scenario where shoreline retreat is projected in all settings. Given the limited accommodation space within saltmarshes at Westernport Bay, sedimentation will not be sufficient to maintain tidal positions and landward retreat will be critical for maintenance of saltmarsh biodiversity. This will require planning decisions to facilitate tidal incursions and conserve retreat pathways.