Relative Deposition Rates Research Articles

Morphology of films deposited on the sidewall during the Bosch process using C4F8 plasmas

In the Bosch process, C4F8 plasmas are used to deposit passivation films. In this study, the passivation films were deposited in micro-scale trenches by changing the C4F8 flow rate, ICP power, and pressure, and their cross sections were observed by scanning electron microscopy. The results showed that the morphology of the passivation film and its relative deposition rate at each depth varied depending on the plasma discharge conditions. There is a correlation between the C–CF x bond content and the morphology of passivation films, with high C–CF x bond content resulting in smooth morphology and low C–CF x bond content resulting in a rough morphology. Furthermore, it was found that ion bombardment reduced the roughness of the passivation film. Through these experiments, we also found the possibility of controlling the deposition rate of the passivation film at each trench depth by adjusting the plasma discharge conditions.

The Long-Term Deep Loessal Sediments of Northeast China: Loess or Loessal Paleosols?

Previous research assumed deep buried loess as the initial composition of the overlying paleosol and failed to address the long-term continuous pedogenic weathering history in the deep loess-paleosol sequence, which was attributed to little understanding on the difference between loess and paleosol in the long-term deep loess-paleosol sequence. To distinguish between the loess and paleosol, in the long-term deep loess-paleosol sequence in northeast China, the morphology, dust deposition fluxes, geochemical characteristics, magnetic susceptibility, and grain size distributions were investigated. Results showed that the loess layers buried at depth could be differentiated from the paleosol by their poor pedogenic development. The presence of coarser grains in the loess as well as lesser amounts of clay and Fe–Mn coatings compared to paleosol indicated weaker weathering of the loess. Also, optical iron clay films deposited on the surface of the skeleton particles were less visible in the loesses than in the paleosols. From the loess evolution perspective, the pedogenic formation process of the newly formed loess soils should be considered as important as that of the reddish paleosol layer based on criteria of formation time, depth within profile, and morphological characteristics. The formation of the reddish or yellowish paleosol layer was constrained by pedogenic environments associated with climatic change and by the relative rates of deposition and pedogenesis. The terms “loessal paleosol” and “loessal paleosol sequence” are suggested to aid in systematically and consistently addressing the long-term pedogenic weathering evolution recorded in the complex formation of deep loess and paleosol sequences in pedology research. The long-term deep loessal sediments of Northeast China are loessal paleosols, which cannot be simply used as a reference for the overlying paleosol and be deducted from pedogenesis consideration.

Asymmetric Interfacet Adatom Migration as a Mode of Anisotropic Nanocrystal Growth.

Crystals are known to grow nonclassically or via four classical modes (the layer-by-layer, dislocation-driven, dendritic, and normal modes, which generally involve minimal interfacet surface diffusion). The field of nanoscience considers this framework to interpret how nanocrystals grow; yet, the growth of many anisotropic nanocrystals remains enigmatic, suggesting that the framework may be incomplete. Here, we study the solution-phase growth of pentatwinned Au nanorods without Br, Ag, or surfactants. Lower supersaturation conditions favored anisotropic growth, which appeared at variance with the known modes. Temporal electron microscopy revealed kinetically limited adatom funneling, as adatoms diffused asymmetrically along the vicinal facets (situated inbetween the {100} side-facets and {111} end-facets) of our nanorods. These vicinal facets were perpetuated throughout the synthesis and, especially at lower supersaturation, facilitated {100}-to-vicinal-to-{111} adatom diffusion. We derived a growth model from classical theory in view of our findings, which showed that our experimental growth kinetics were consistent with nanorods growing via two modes simultaneously: radial growth occurred via the layer-by-layer mode on {100} side-facets, whereas the asymmetric interfacet diffusion of adatoms to {111} end-facets mediated longitudinal growth. Thus, shape anisotropy was not driven by modulating the relative rates of monomer deposition on different facets, as conventionally thought, but rather by modulating the relative rates of monomer integration via interfacet diffusion. This work shows how controlling supersaturation, a thermodynamic parameter, can uncover distinct kinetic phenomena on nanocrystals, such as asymmetric interfacet surface diffusion and a fundamental growth mode for which monomer deposition and integration occur on different facets.

Controlled compositional gradients of electroformed gold and silver

Motivated by an interest in high-pressure research, thick (>1 mm) compositionally graded gold/silver (Au/Ag) films were electroformed. Systematic studies were performed to understand the role of processing temperature on the nucleation and growth kinetics and associated microstructure. Furthermore, as the electrolyte composition is continuously changing during the experiment, systematic studies were performed to correlate electrochemical parameters with film morphology and composition. The results showed that the nucleation pathways and relative deposition rate of Au and Ag are heavily dependent on the processing temperature. A procedure to ramp the temperature while continuously pumping an Au electrolyte into an initial Ag electrolyte to produce the graded film is presented. The obtained film is comprised of a segment of pure Au followed by a complete compositional gradient and ending with a segment of pure Ag across 1.5 mm. The results presented here describe a general framework to fabricate gradients of other materials through electrodeposition.

Predicting the composition of W-B-C coatings sputtered from industrial cylindrical segmented target

Computational methods have been gaining more and more attention as they provide a powerful tool for increasing efficiency in the industrial use of magnetron sputtering and provide results from which experimental work benefits. This work presents an approach for the prediction of the composition and the deposition rate of the coatings. The combination of SDTrimSP and SiMTra provides a framework for the simulation of the deposition process. The chemical composition and the deposition rate of industrially sputtered W-B-C coatings were investigated. An industrial batch coater with a complex geometry was modelled. A cylindrical rotating sputter source was mounted with a segmented target composed of W, B4C, and C segments. The simulated chemical composition and the relative deposition rate were verified and validated by experiments. A correlation between the chemical composition and target segment placement is presented, and the influence of substrate movement on the chemical composition is discussed. A single-axis rotation of the substrate placed on an industrial carousel causes a lowering of the content of tungsten in the coatings in comparison to statically placed substrates in front of the sputter source. The simulations uncover the distinct trajectories of the heavy and light particles. The different transport of particles from target to substrate results in the observed shift of chemical composition and also explains the inherent nanolayering of the non-reactively deposited coatings in the industrial batch coater.

Toward Constraining Sources of Lithogenic Metals in the Northern Gulf of Mexico

AbstractNorth African dust is known to be deposited in the Gulf of Mexico, but its deposition rate and associated supply of lithogenic dissolved metals, such as the abiotic metal thorium or the micronutrient metal iron, have not been well‐quantified. 232Th is an isotope with similar sources as iron and its input can be quantified using radiogenic 230Th. By comparing dissolved 232Th fluxes at three sites in the northern Gulf of Mexico with upwind sites in the North Atlantic, we place an upper bound on North African dust contributions to 232Th and Fe in the Gulf of Mexico, which is about 30% of the total input. Precision on this bound is hindered by uncertainty in the relative rates of dust deposition in the North Atlantic and the northern Gulf of Mexico. Based on available radium data, shelf sources, including rivers, submarine groundwater discharge, and benthic sedimentary releases are likely as important if not more important than dust in the budget of lithogenic metals in the Gulf of Mexico. In other words, it is likely there is no one dominant source of Th and Fe in the Gulf of Mexico. Finally, our estimated Fe input in the northern Gulf of Mexico implies an Fe residence time of less than 6 months, similar to that in the North Atlantic despite significantly higher supply rates in the Gulf of Mexico.

Insight into the surface composition of bimetallic nanocatalysts obtained from microemulsions

The enhancement of catalysts efficiency of bimetallic nanoparticles depends on the ability to exert control over surface composition. However, results relating surface composition and feeding solution of bimetallic nanoparticles synthesized in microemulsions are controversial and apparently contradictory. In order to comprehend how the resulting surface can be modified under different synthesis conditions and for different pairs of metals, a computer simulation study was carried out. The resulting surface compositions are explained based on the relative rates of deposition of the two metals, which depend on the particular metal pair, the concentration of reactants and the microemulsion composition. This study provides a satisfactory understanding of experimental results and allows us to identify the main factors affecting the nanoparticle’s surface composition. Consequently, concrete and practical guidelines can be established to facilitate the experimental synthesis of bimetallic nanoparticles with tailored surfaces.

Personal deposited dose and its influencing factors at several Greek sites: an analysis in respect to seasonal and diurnal variations.

The deposited dose in the human respiratory tract and its influencing factors were investigated for 8 urban/suburban locations within Greek cities. A dosimetry model (ExDoM2) was implemented assuming a 24-h exposure scenario to ambient PM10 whereby regional deposition rates were obtained. Simulations were performed considering three cases (Sahara dust, cold, and warm periods) with seasonal and diurnal variations examining the relative sources and other influencing factors in each case. Health risk indexes such as the relative risk and attributable fraction were also estimated. Overall, higher daily deposited dose was obtained for all urban compared with suburban locations (p < 0.05) and for cold compared with the warm periods (252-820 μg for cold period and 300-686 μg for warm period) for all locations. This finding was associated with increased deposition rate on cold period during evening/night hours, as a result of significant heating emissions. Besides that, most of the urban locations showed relative comparable deposition rates during the day, compared with the daily mean, for the two periods (cold and warm), indicating that urban-associated sources such as exhaust emissions and road dust resuspension contribute similarly to the deposited dose irrespectively of the season. Finally, the highest deposited dose was obtained during Sahara dust events ranged from 1881 to 4648 μg.

Tailoring plasmonic properties of Ag-SiO2 nanorods and their surface-enhanced Raman scattering activities

Due to a wide range of applications, plasmonic properties of metal nanoparticles have been widely explored, while the understanding of plasmonic behaviors of dielectric-metal composites is still limited. Herein, as a proof of concept, the relationship between compositions and plasmonic behaviors of Ag-SiO2 composites was investigated considering their extensive utilization as SERS substrates. Ag-SiO2 nanorods with regulated compositions were fabricated via glancing angle co-deposition. By increasing Ag relative deposition rate, structure of Ag-SiO2 nanorods evolves from Ag nanoparticles embedded into SiO2 matrix to quasi-one-dimensional Ag structure, inducing plasmon resonance changes over a wide range and corresponding SERS activity variations. Plasmonic resonance resulted from individual Ag nanoparticle, coupling effect of Ag nanoparticles, and quasi-one-dimensional Ag nanorods can be observed successively as Ag content increases in Ag-SiO2 nanorods. Meanwhile, SERS performance of Ag-SiO2 corresponds well with their plasmon behaviors and the maximum SERS signal was obtained from Ag-SiO2 composites with quasi-one-dimensional Ag structure. With the optimization of plasmon and SERS performance of Ag-SiO2 nanorods, we demonstrated the potential use of Ag-SiO2 nanorods in real applications as SERS chemical sensors for the detection of melamine.

Tidal amplification and along‐strike process variability in a mixed‐energy paralic system prograding onto a low accommodation shelf, Edgeøya, Svalbard

AbstractThe study describes the depositional development and sediment partitioning in a prograding paralic Triassic succession. The deposits are associated with the advance of large prism‐scale clinoforms across a shallower platform area. Approaching the platform, the limited accommodation and associated relative higher rates of deposition generated straighter clinoforms with lower foreset angles. The vertical restriction across the platform is interpreted to have amplified the tidal signature. Sediment was redistributed from the coast into increasingly sandy delta‐front deposits, compared to offshore equivalents. The deposits comprise extensive compound dune fields of amalgamated and increasingly clean sandbodies up‐section. Rapid deposition of significant amounts of sand led to differential subsidence and growth‐faulting in the delta front, with downthrown fault blocks further amplifying the tidal energy through funnelling. A mixed‐energy environment created along‐strike variability along the delta front with sedimentation governing process‐regime. Areas of lower sedimentation were reworked by wave and storm‐action, whereas high sedimentation rates preserved fluvially dominated mouth bars. A major transgression, however, favoured tidally dominated deposits also in these areas, attributed to increasing rugosity of the coastline. Formation of an extensive subaqueous platform between the coast and delta front dampened incoming wave energy, and tidally dominated deposits dominate the near‐shore successions. Meanwhile formation of wave‐built sand‐bars atop the platform attest to continued wave influence. The strong tidal regime led to the development of a heterolithic near‐shore tidally dominated channel system, and sandier fluvial channels up‐river. The highly meandering tidal channels incising the subaqueous platform form kilometre wide successions of inclined heterolithic stratification. The fluvially dominated channels which govern deposition on the delta plain are narrower and slightly less deep, straighter, generally symmetric and filled with cleaner sands. This study provides important insight into tidal amplification and sand redistribution during shallowing on a wide shelf, along with along‐strike process‐regime variability resulting from variations in sediment influx.

Kinetics of extraction from water solutions of Fe&lt;sup&gt;3+&lt;/sup&gt;, Cu&lt;sup&gt;2+&lt;/sup&gt; and Pb&lt;sup&gt;2+&lt;/sup&gt; + ions by filter loading, obtained by blinding plasters

In this study, we investigated the kinetics of extraction from aqueous solutions of Fe3+, Cu2+ and Pb2+ by filter loadings, derived from the steelmaking slags. A formal kinetic approach based on the relationship between the relative deposition rate (α) and time (τ) was used to estimate the mechanism and kinetic parameters of the deposition process). From the set of equations are selected those that in a given region of the degree of completion of the process gave the minimum value of the variance, that is, described the process in the system at this stage with the maximum probability. Three models that best correspond to real processes are selected. It was found that the deposition process at the initial stage limits the chemical stage of nucleation (formation of crystalline precipitate), then – the reaction at the interface (formation of a continuous layer of reaction products on the surface of the nuclei), and at the final stage – the growth of a continuous layer of reaction products.

Canopy spray deposition and related mortality impacts of commonly used insecticides on Drosophila suzukii Matsumura (Diptera: Drosophilidae) populations in blueberry.

Insecticide applications in blueberry production systems play a crucial role in the control of Drosophila suzukii populations. Here, quantitative spray deposition patterns were obtained under replicated field experiments in blueberry during two field seasons with three sprayers, i.e. cannon, electrostatic, and air-blast. Seven insecticides were tested (at 6 hours using a Potter spray tower) to determine the mortality data for adult D. suzukii. Spray deposition and mortality data for adult D. suzukii were used to create model simulations for insect populations. Model simulations included field deposition rates of sprayers and insecticide mortality as factors. Simulations were applied in different combinations with five applications over a 6-week period. Relative deposition rates for the cannon sprayer were elevated in the upper zones of the canopy, whereas for the air-blast sprayer, deposition was greater in the bottom zones. Electrostatic spray deposition was relatively uniform within the six canopy zones. Clear trends in D. suzukii laboratory mortality were found with lowest to highest mortality recorded for phosmet, spinetoram, spinosad, malathion, cyantraniliprole, zeta-cypermethrin, and methomyl respectively. Maximum D. suzukii population impacts, as shown by model outputs, were observed with air-blast sprayers together with zeta-cypermethrin. The electrostatic sprayer had the least variable canopy deposition among the three types of spray equipment, and the air-blast sprayer had the highest overall deposition rates. This study provides new hypotheses that can be used for field verification with these spray technologies and insecticides as key factors. © 2019 Society of Chemical Industry.

Die Hochleistungsmikrowellenquelle Miro

SummaryThe high‐performance microwave source Miro – Plasma characterization and applications in PECVD and combination sputtering processesTo evaluate the potential of the high‐efficiency microwave source Miro 200 CI the properties of plasma processes were investigated focusing at PECVD coatings of a‐C:H‐ and SiOx as relevant applications. The sources were also intensively characterized by plasma diagnostic methods, e.g. by optical emission spectroscopy and electrical plasma probes. The analysis of the real efficiency of individual sources with slight changes in construction could be used to come to an optimized design. The Miro sources are able to create an extensive working volume showing relative homogeneous deposition rates of currently 35μm/h for a‐C:H and 25 μm/h for SiOx. An arrangement of multiple sources enables PECVD processes for large area coating at a pressure level close to those commonly used with PVD sources. So, post‐oxidation of sputtered layers with the Miro source could be used beneficially to obtain optical oxide layers with lower absorption. Combinations with HIPIMS sputter sources lead to efficient deposition processes of coatings for tribological applications.

Combustion Characteristics of Plant Chemical Polyol Waste Liquor in a Pilot Water-Cooled Incinerator

In the production of plant chemical alcohol, a large amount of salty high-concentration organic waste liquid is by-produced, in which a large amount of high-value sodium tungstate and chemical heat energy are contained. Through the design of the pilot water-cooled incinerator, the operating parameters and the characteristics of alkali ash deposition of the waste incinerator were tested. The pilot incinerator is a natural-cycle steam boiler, has a full water-cooled II-type structure, with liquid slag discharge, and the furnace design has selected reasonable volumetric heat load and flue gas residence time. Combustion distribution is the core parameter affecting the combustion of waste liquid. Studies have shown that increasing the primary air rate and the excess air coefficient are beneficial to improve the combustion performance of waste liquid, increase steam production, and reduce CO and SO2 emissions in flue gas, but also increase the concentration of NO. When the excess air ratio was 1.2, and the primary air ratio was 0.65, the NO concentration in the tail flue gas was less than 10 ppm, and the SO2 concentration was zero. The TG-DTA method measured that when the alkali ash melting temperature was less than 587 °C, the alkali ash had strong adhesion in the high temperature zone of the incinerator and less deposition in the low temperature region of the tail. The alkali ash deposition rate and relative deposition rate were used to quantitatively study the characteristic of alkali ash deposition.

Dynamics of the mineral composition and deposition rates in the empty body of entire males, castrates and female pigs

Mineral composition and relative deposition rates in the pig’s body are used to assess the mineral net requirements for growth and input–output balances. The study aimed to examine the dynamics of changes in mineral composition and deposition rates in the empty body (EB) from birth to 140 kg BW depending on dietary protein supply. In the experiment, 66 entire male, 58 castrated and 66 female Swiss Large White pigs were used to determine body composition at birth, 10, 20 kg and at 20 kg intervals from 40 to 140 kg BW. From 20 kg BW, they had either ad libitum access to a control grower and finisher diet or a grower and finisher diet containing 80% CP, lysine, methione+cystine, threonine and tryptophan of the control diet. Each EB fraction (carcass, organs and empty intestines, blood and bile) was weighed and analyzed for water, ash, calcium, phosphorous, magnesium, potassium, sodium, copper, iron, manganese and zinc contents. Allometric relationships between the amount of each mineral in the EB and the EB weight (EBW) were fitted. The R2 of the allometric equations was above 0.92, except for copper and manganese (below 0.33), revealing the EBW as an excellent explanatory variable of the analyzed amounts. The copper and manganese composition in the EB were extremely low and variable which explain the low R2. Except for zinc, all mineral relative deposition rates decreased with increasing EBW. The amount of ash, calcium and phosphorus in the EB was not affected by the diet, but when expressed relative to body protein these minerals were increased when pigs were fed the low protein diet. This suggests an independent protein deposition and bone mineralization when animals are fed diets limiting in protein content. The diet also affected the amount of potassium in the EB which was greater when the low protein diet was fed. The gender only affected the amounts of potassium and sodium in the EB which were greater in entire males. Entire males had also greater amounts of water in the EB, which may explain the observed effect of gender on these two electrolytes. Finally, gender and dietary protein did not affect to a sufficient relevant way the body mineral composition and deposition rates in the EB, suggesting that their distinction may not be necessary to assess, on BW basis, the mineral net requirements for growth and the exported amount of minerals in input–output balances.

Characterisation of the heterojunction microstructure for electrodeposited vertical ZnO nanorods on CVD-graphene

A low-cost heterostructure of a wide-bandgap nanostructured semiconductor on top of a transparent conductor (TC) fabricated from abundant sustainable materials is of great interest for optoelectronic devices, such as heterojunction photovoltaic cells. Due to its high optical transparency and electron mobility, graphene is an attractive carbon-based material to replace the costly traditional TCs (i.e. ITO), which pose health hazards and destructive environmental impact thorough their life cycle. However, for the industrial application of graphene as TC it is necessary to interface it with other materials, like oxides, while maintaining the sp2 network that provides its excellent electronic properties. We report the optimized electrodeposition of ZnO on graphene to obtain a textured layer of vertically aligned crystalline semiconducting nanorods (ZVNRs) evenly coating the graphene surface. Lattice distortions and mosaicity in the crystals indicate that the ZVNRs grow under out-of-plane compressive strain. The stability of the sp2 network of graphene during in situ growth of ZnO is demonstrated using Raman spectroscopy from the front and backside of the heterostructure, in a novel approach to investigate junctions of 2D–3D nanomaterials. Despite the structural stability of graphene, its R□ is found to increase by ∼100% with ZVNRs electrodeposition, which is attributed to reduction of mobility due to charge carrier scattering, reduction of carrier concentration due to doping, and/or interfacial strain. The cathodic electrodeposition is demonstrated to be an effective and versatile method to grow crystalline nanostructures in the surface of single layer-graphene while protecting its sp2 hybridization, and it provides relative fast deposition rates, affordability, and low processing temperatures that would allow using polymeric flexible substrates and. These findings on interfacial properties are important to advance the functionality of graphene as TC material and develop nano-heterostructures for myriad technological applications.

Perovskite-Perovskite Homojunctions via Compositional Doping.

One of the most important properties of semiconductors is the possibility of controlling their electronic behavior via intentional doping. Despite the unprecedented progress in the understanding of hybrid metal halide perovskites, extrinsic doping of perovskite remains nearly unexplored and perovskite-perovskite homojunctions have not been reported. Here we present a perovskite-perovskite homojunction obtained by vacuum deposition of stoichiometrically tuned methylammonium lead iodide (MAPI) films. Doping is realized by adjusting the relative deposition rates of MAI and PbI2, obtaining p-type (MAI excess) and n-type (MAI defect) MAPI. The successful stoichiometry change in the thin films is confirmed by infrared spectroscopy, which allows us to determine the MA content in the films. We analyzed the resulting thin-film junction by cross-sectional scanning Kelvin probe microscopy (SKPM) and found a contact potential difference (CPD) of 250 mV between the two differently doped perovskite layers. Planar diodes built with the perovskite-perovskite homojunction show the feasibility of our approach for implementation in devices.

Deposition rates of viruses and bacteria above the atmospheric boundary layer.

Aerosolization of soil-dust and organic aggregates in sea spray facilitates the long-range transport of bacteria, and likely viruses across the free atmosphere. Although long-distance transport occurs, there are many uncertainties associated with their deposition rates. Here, we demonstrate that even in pristine environments, above the atmospheric boundary layer, the downward flux of viruses ranged from 0.26 × 109 to >7 × 109 m-2 per day. These deposition rates were 9-461 times greater than the rates for bacteria, which ranged from 0.3 × 107 to >8 × 107 m-2 per day. The highest relative deposition rates for viruses were associated with atmospheric transport from marine rather than terrestrial sources. Deposition rates of bacteria were significantly higher during rain events and Saharan dust intrusions, whereas, rainfall did not significantly influence virus deposition. Virus deposition rates were positively correlated with organic aerosols <0.7 μm, whereas, bacteria were primarily associated with organic aerosols >0.7 μm, implying that viruses could have longer residence times in the atmosphere and, consequently, will be dispersed further. These results provide an explanation for enigmatic observations that viruses with very high genetic identity can be found in very distant and different environments.

Developments in Hybrid Electro-Electroless Deposition (HEED)

Hybrid electro-electroless deposition (HEED) is a novel thin film metal deposition technique that combines electroplating and electroless deposition within a single electrolyte. The hybridization of HEED is the result of each deposition process targeting a distinct metal ion, or combination of ions, for reduction. The nature of the deposit is determined by the composition, pH, and temperature of the electrolyte as well as the electroplating potential applied; all of which affect the relative deposition rate of each process. Composite, alloyed, or compositionally modulated layered deposits can all readily be formed using HEED. This work details advancements in controlling the composition and production of both HEED alloys and multi-layers. HEED alloys are produced by using electroplating to either preferentially deposit one component of the electroless alloy, or including a new metal into the electroless deposit. The deposition of Zn enhanced Ni-Zn-P HEED alloys, representing the former case, is shown in connection to the production of corrosion resistant coatings. The electroless process produces coatings over the entire surface while electroplating provides increased Zn content in electroplated regions. The formation of concentration gradients within the coating provides control over where corrosion is most likely to occur. Energy-dispersive X-ray spectroscopy (EDS) was used to determine an increase in Zn content from 26% using electroless deposition to 50% using HEED [1]. The process was carried out on both Cu substrate and Mg alloy substrates. Compositionally modulated HEED, or multi-layer HEED, deposits are produced in a similar fashion to traditionally electroplated multi-layer deposits by modulating the applied deposition potential [1, 2]. Provided appropriate conditions and ion choice, slowing the electroless deposition rate minimizes inclusion of the electroless alloy or metal. With HEED, metals of similar nobility, such as Ni and Co, can be deposited in a multi-layered arrangement [2]. In the multi-layered configuration Ni-P is electrolessly deposited while Co is reduced using electroplating. The atomic composition of the electroless Ni-P layers, tested on Sn/Pd treated glass, was consistently 76% Ni, 22% P, with no more than 2% Co [2], consistent with Ni3P. Within an acidic electrolyte the electroless Ni-P layers are effectively free of Co while the purity of electroplated Co layers is dependent on the electroless deposition rate and relative Co2+ ion availability in solution. Adjusting the pH to the alkaline regime results in alloying of each layer as Co is co-deposited in the electroless deposition phase. Figure 1 shows the competition between Co electroplating and electroless Ni-P deposition at low current density 0.95 A∙dm-2 on a Cu substrate [2]. The low current density slows electroplating while the temperature promotes hastened electroless deposition. The resulting deposit is a composite of each distinct process with the electroless deposition material, EDS Spot 1, and electroplated material, EDS Spot 2, shown to have distinct structures and composition. Increasing the current density to 3.8 A∙dm-2 produces homogeneous alloys as electroplating becomes the dominant process. Lowering the temperature of the electrolyte further increases the dominance of electroplating. [1] Robert Petro and Mordechay Schlesinger, “Development of Hybrid Electro-Electroless Deposit (HEED) Coatings and Applications”, Journal of The Electrochemical Society, 161(10), (2014), p.D1-D6 [2] Robert Petro and Mordechay Schlesinger, “Deposition of Cobalt-Nickel Hybrid Electro-Electroless Deposited (HEED) Modulated Multilayers”, Journal of The Electrochemical Society, 162(4), (2015), p.D154-D158 Figure 1

Comparative Study of Hydrogen and Argon Dilution Effects in Amorphous SiC Thin Films Deposited by Plasma Enhanced Chemical Vapor Deposition.

Amorphous SiC thin films were deposited from a mixture of silane and methane gas with the separate hydrogen and Argon dilution by using the plasma enhanced chemical vapor deposition process. The effects of different dilution gas on the chemical composition, bonding states, microstructure and optical property of the films were studied and compared. For the films with H2 dilution, the higher hydrogen content passivated more Si dangling bonds so that the formation of nanocrystalline silicon was inhibited and the films were kept in amorphous state. The amorphous nature along with the higher carbon content of the films led to the larger optical band gap E(opt), of 2.63 eV. In contrast, for the films with Ar dilution, they presented a relative higher deposition rate due to the rapid decomposition of silane accelerated by Ar. The Si-Si bonds were formed and they had a higher tendency to precipitate silicon quantum dots.