Discontinuous Films Research Articles

Aluminum-induced crystallization of silicon suboxide thin films

Polycrystalline silicon (poly-Si) thin films are fabricated by aluminum-induced crystallization (AIC) of amorphous silicon suboxide (a-SiOx, x = 0.22) at 550 °C for 20 h. AIC of a-SiO0.22 via thermal annealing of a-SiO0.22/Al bilayer structures leads to layer exchange with the formation of poly-Si films with (111) preferential orientation and high-crystalline quality-coated with a layer of a mixture of Al, Si, and O atoms with inclusions of silicon nanocrystallites. The initial a-SiO0.22/Al thickness ratio approximately equal to 1 provides the formation of a discontinuous poly-Si film with a crystallized fraction of 85%, as shown by optical microscopy.

Polymer film dewetting for fabrication of out-of-autoclave prepreg with high through-thickness permeability

Polymer film dewetting on a substrate (independent of fiber bed architecture) was explored, developed, and demonstrated as a method to produce out-of-autoclave, vacuum bag-only (OoA/VBO) prepregs with high transverse permeability and process robustness. The dimensions of the surface openings created by dewetting were measured,and thepercent surface area exposed was calculated. Prepregs were fabricated with continuous and dewetted (discontinuous) films to producetrial laminates. The laminates were cured under both standard and sub-optimal conditions, and were characterized before, during, and after cure.Laminates fabricated with dewetted resin consistentlyachieved near-zero porosity. In contrast,laminates with continuous filmdisplayed high levels of porosity,particularly during sub-optimal cure. The findings demonstrate that dewetting can be used effectively to produce OoA prepregs with high through-thickness permeability, whichcan yieldporosity-free laminates via VBO processing. Furthermore, these results elucidate aspects of resin dewetting that are critical in thecreation ofrobust OoA prepregs.

Process Optimization of through Silicon Vias Metallization Using Reduced Graphene Oxide As a Conductive Layer

Three-dimensional (3D) IC chip stacking has been proposed for a long time. An interposer designed between two chips for interconnection [i.e., through silicon vias (TSVs)] is a bridge for vertical signal transmission. Recently, reduced Graphene Oxide (rGO) has also been developed because it not only is a good conductor, but also it can be grafted onto the surface of many substrates and makes them be conductive through rGO grafting process. TSV is a silicon-based substrate, so self-assembled monolayer (SAM) of amino-silane is usually used as an adhesive layer in the rGO grafting process, and it can form a thin film with positive charges, which can adsorb the functional groups of GO sheets due to charge attraction. After GO is grafted onto the surface, a chemical reducer is used to reduce the grafted GO to rGO. However, silane must be dissolved in an organic solvent for stabilization. Otherwise, it easily forms “islands” on the surface, which then cause non-uniform and discontinuous rGO film. In this work, deionized water was employed to replace the organic solvent to dissolve the amino-silane. Effects of operating parameters, surface treatments and modifications on rGO grafting performance were investigated to improve the uniformity and continuity of the grafted rGO using several analysis methods and instruments, like water contact angle, atomic force microscopy(AFM) and conductive atomic force microscopy(C-AFM), etc. Cross-section images of TSVs after copper and cobalt electroplating were also used to evaluate the filling performance and uniformity. Eventually, a stable and optimized aqueous rGO grafting process is developed and can be used as a conducting layer of TSV for copper and cobalt superfilling. Keywords: Through Silicon Via, Electroplating, reduced Graphene Oxide, 3D IC Reference: Songfeng, and C. Hui-Ming, “The Reduction of Graphene oxide ”, Carbon., 2012, 50, 3210-3228. Figure1. Scheme of the rGO grafting process. TSV was immersed in Beaker A for surface pre-treatment, surface modification with amino-silane was carried out in Beaker B, the GO grafting step was performed in Beaker C, and GO reduction was conducted in Beaker D. Figure 1

The Ablation and Oxidation Behaviors of SiC Coatings on Graphite Prepared by Slurry Sintering and Pack Cementation

SiC coatings were generated on graphite using slurry sintering (SS) and pack cementation (PC). The samples’ ablation features were assessed by an oxyacetylene torch. The rates of mass ablation of the PC–SiC and SS–SiC coatings were approximated 2.17 × 10−3 and 9.52 × 10−3 g s−1, respectively, decreased by 84.1 and 29.6% compared to the uncoated samples. It was mainly attributed to the formation of a SiO2 layer on the surface. The continuous SiO2 molten film formed via the PC–SiC oxidation generates a sealing mechanism which can be an obstacle against the oxygen diffusion and hinder more ablation. This is while discontinuous SiO2 film formed from the thin SS–SiC cannot protect the graphite effectively. The non-isothermal oxidation test shows that without the SiC coating, the sample weight is lost largely from 25 to 1500 °C, and its weight loss was 2.2% after the TGA. However, after coating, the samples possessed excellent oxidation protection and weight losses of SS–SiC and PC–SiC coatings are down to 1.3 and 0.6%, respectively. The more oxidation of the graphite substrate occurred due to the formation of macrocracks in the coating during the TGA and also the formation of holes on SiO2 glass layer owing to release of CO or CO2.

Electrical percolation through a discontinuous Au nanoparticle film

Au thin films of thicknesses ranging from 5 to 20 nm were grown in UHV through physical vapour deposition on glass substrates decorated with Pt interdigitated electrodes with 5 μm separation. As expected, a gradual decrease in the electrical resistance of the films was observed as growth proceeded; however, when the average film thickness was greater than around 11 nm, the resistance decrease was not smooth but occurred in discrete steps. These resistance steps are attributed to the formation of electrical percolation pathways connecting the electrodes. The samples were then annealed at temperatures between 200 °C and 500 °C for periods of 1 to 22 h with the aim of producing insulating nanoparticle films. Dewetting of the Au films produces nanoparticles whose size and separation depend on annealing temperature and time, as well as the initial thickness of the Au film. The complex electrical resistance behaviour of the film was also monitored during the dewetting process.

Graphite Surface Microhardening with Femtosecond Laser Pulses

The effects of direct femtosecond laser processing of a polycrystalline graphite surface are experimentally investigated. The functional graphite surfaces are fabricated at laser intensity of ~1017 W/cm2 in vacuum and then thoroughly analyzed by means of Raman spectroscopy and nanoindentation test. The measured Raman spectra at 257 nm show presence of an amorphous carbon phase containing sp3 hybridized carbon atoms and a discontinuous nanocrystalline diamond film, while the results of microhardness measurements demonstrate a sixteen-fold increase in microhardness as compared to the unirradiated graphite surface. The modulus of elasticity is found to increase nearly by 3.4 times.

Numerical Simulation Study on Characteristics of Airtight Water Film with Flow Deflectors

In practical use, there is shrinkage in the width direction in existing overflow water film. This study introduces the " flow deflectors " to solve the problem of discontinuous water film. According to the principle of the experimental devices, the model was established by FLOW-3D software and the corresponding boundary conditions were set up, the minimum size of the grid was 0.25mm × 0.25mm × 0.25mm. The film model was investigated under ten working conditions with three factors. Through the analysis of the distribution curves of velocities and thickness, impacts of unit width flux, tank width and the distance between the flow deflectors on the velocity and thickness of the liquid film were obtained. The results indicated that the water film was able to keep continuous and airtight with flow deflectors. The variation law of water film with unit width flux was obtained and a correlation formula was proposed according to Nusselt correlation. And, it was found that the tank width has little influence on the water film itself. The "dry zones" were also founded on the film when the distance between flow deflectors increased.

Morphology of Polymer Film Coatings Produced in a Barrier Gas Discharge at Atmospheric Pressure

The technique of deposition of polymer films from the barrier gas discharge plasma on top of dielectric substrates is developed. The film precursor is a monomer material highly dispersed in a transport plasma gas. The plasma formation of the continuous polymer film can be divided into two stages. The first stage is deposition of liquid monomer droplets with subsequent polymerization on the dielectric barrier surface resulting in growth of a discontinuous film. It is found that the ratio of the height of droplets to their lateral size is almost constant and for polystyrene it is equal to ~0.01. The second stage is expansion of the droplets into islands and their coalescence into a continuous polymer film on the dielectric barrier surface. The polymer coating thickness and the amount of cross bonds essentially depend on the current density and concentration of the monomer in the transport discharge gas. A continuous polymer film, which is not contaminated with the monomer destruction products, can be obtained in the current density range of 7–25 mA/cm2. Experiments with several monomers, like methylmethacrylate, styrene and acrylonitrile, have shown that the growth rate is maximal for monomers with oxygen-free molecules. At the same time, a higher growth rate provides low cross-bond coatings, whereas to get high density of the cross-linked bonds one has to utilize low deposition rates. The minimal thickness at which continuity of the film is achieved increases when the monomer concentration in the plasma rises. In general, the coating thickness depends linearly on the discharge current density; the particular figures depend on the type and concentration of the monomer. The technological parameters are established and given for the three aforementioned monomers.

Deposition, Characterization and Evaluation of Monolayer and Multilayer Ni, Ni–P and Ni–P–Nano ZnOp Coatings

Ni, Ni–P and Ni–P–ZnOp monolayer films along with multilayer coatings containing different arrangements of these layers were produced on steel substrates by electrodeposition and electroless deposition techniques. Co-deposition of ZnO nano-particles, as well as morphology, cross-section, microstructure and microhardness of coatings were investigated. Corrosion behaviors of monolayer coatings were studied by potentiodynamic polarization and electrochemical impedance spectroscopy techniques, and the results were compared to multilayer films. Results revealed that, Ni–P–1.5 vol% ZnOp monolayer film obtained from a bath with 4 g L−1 of these particles had the highest hardness between all samples. Further addition of nano-particles to the bath lead to the formation of discontinuous films. Most of the multilayer coatings with different arrangements exhibited higher corrosion resistance as compared to monolayer films. Corrosion current density of three-layer Ni–P–ZnOp/Ni/Ni–P coating, considered as the most corrosion resistant film, was about 538 times lower than monolayer Ni–P coating.

Study of initial stages of thin film growth by means of atomistic computer simulation and image analysis: Comparison with experimental data

The initial stages of metal film growth were studied by computer experiment. The structures were generated by an atomistic model combining the molecular dynamics and Monte Carlo approaches and the analysis of obtained structures was performed by image processing algorithms. Film morphology was tested by several methods and it was found that especially Voronoi tessellation and Quadrat Counts methods are best suited for a description of spatial distribution of objects. The same morphological analysis was applied to experimental data – to micrographs of discontinuous films of Ag, Au and In grown on dielectric or graphite substrates. It was found that for small evaporation rates the atomistic model is in a good agreement with experiments. However, when increasing the evaporation rates the effect of secondary nucleation starts to be pronounced and a discrepancy between modelled and experimentally derived morphological results occurs. This effect was demonstrated for indium films with intensive secondary nucleation.

A Comparative Study of Hydrogen-Induced Cracking Resistances of API 5L B and X52MS Carbon Steels

Susceptibility to hydrogen-induced cracking of API 5L B and X52MS low-carbon steels in NACE 177-A, 177-B, and 284-B solutions has been investigated by the present work. A metallographic analysis of these steels was performed before and after NACE TM0284 standard testing. Corrosion products were characterized by scanning electron microscopy and X-ray dispersive energy spectrometry, which were subsequently identified by X-ray diffraction. Thus it was found that pH directly affects the solubility of corrosion products and hydrogen permeation. Both steels showed generalized corrosion in solution 177-A, and a discontinuous film was formed on their surfaces in solution 177-B; however, only the API 5L B steel failed the HIC test and exhibited greater crack length ratio in solution 177-A. In solution 284-B whose pH is higher, the steels exhibited thick mackinawite films with no internal cracking.

Growth Behavior Evolution of Al2O3 Deposited on HOPG by Atomic Layer Deposition

Abstract Al2O3 dielectrics were fabricated on highly ordered pyrolytic graphite (HOPG) by atomic layer deposition (ALD) and the effects of growth temperatures and number of ALD cycles on growth behaviors were studied. It is found that Al2O3 preferentially grows along the step edges which promote the formation of Al2O3 nanowires at the initial stage. Al2O3 nanowires can exist after 100 ALD cycles at 50, 150, and 200 °C, but discontinuous Al2O3 thin films rather than nanowires are evidenced at 100 °C. Moreover, the Al2O3 layers evolve into continuous thin films with increasing number of ALD cycles. It suggests the growth behavior undergoes a transition from three-dimensional mode to quasi two-dimensional mode with increasing number of ALD cycles. The rates of transition and lateral growth are dependent on growth temperatures. Raman spectra indicate that HOPG maintains undamaged and greatly reserves its original properties after the deposition of Al2O3. The results are of great significance to the fabrication of high-quality dielectric layers on graphene as well as the related devices.

Стокс-поляриметрія надтонких острівцевих плівок Au та Sn

The optical properties of ultrathin Au and Sn islet films, obtained by the methods of magnetron sputtering and thermal evaporation, respectively, are considered in this paper. By measuring the Stokes vector of the beam reflected from the samples, polarized and depolarized radiation components were separated. The conditions of the polarization degree dependence on the surface structure for a series of islet films with different morphologies are analyzed. To determine the morphological structure of the metal layer, methods of atomic force microscopy and resistivity measurement were also employed. The parameters of discontinuous film, obtained by optical and non-optical methods, are compared. It is established that with an increase in the angle of radiation incidence onto the samples, the polarization degree of the reflected beam decreases. Such behavior can be explained by the Mie theory of light scattering by particles. The magnitude of depolarizing action of the samples also depends on the morphology of their surface, correlating with the number of inequalities on it. The applied method of Stokes polarimetry, thus, allows one to obtain additional information on the structure of the surface, which is its advantage.

Simultaneous corrosion control and water quality improvement in water distribution systems

Abstract The effects of different dosages of sodium hexametaphosphate and sodium orthophosphate on corrosion inhibition and water quality in two model water distribution systems, and the corrosion inhibition mechanism on pipe walls were investigated. Results show that adding sodium hexametaphosphate and sodium orthophosphate can not only provide a remedy for the damaged cement coating surface, but improve water quality by reducing hardness, turbidity and total iron in cement-coated water distribution systems. The surface exposed to sodium hexametaphosphate was covered by a discontinuous glass-like film, while the other was covered by some phosphate crystals and a thin film. The glass-like film sequestered Ca, Fe and Al on its surface, where calcium hexametaphosphate could be in complex with Fe2O3 or Al2O3 to form the film, while orthophosphate crystals and the thin film were related to Fe and Ca, FePO4 and Ca3(PO4)2 formed and deposited on the surface composing the thin film.

Peculiarity of magnetoresistance of discontinuous ferromagnetic thin films

The magnetoresistive properties of discontinuous ferromagnetic Fe and Co thin films deposited by electron-beam sputtering onto glass substrates at room temperature were investigated. Tunnel magnetoresistance (MR) was observed for all of the as-deposited samples. The maximum MR was observed for Fe thin films with an effective thickness of 17 nm. In the case of the Co thin films, the annealing process led to a change of the type of MR to anisotropic at Co film thicknesses (dCo) of 15 ≤ dCo ≤ 25 nm and to positive isotropic at thicknesses of dCo < 15 nm. By contrast, the MR type of Fe thin films did not change.

Anodic deposition of nanostructured hematite film using agarose gel as template. Application in water splitting

The present study shows the results obtained in anodic electrodeposition of hematite precursor films in agarose gel template and photoelectrochemical characterization of the prepared hematite films. The peak current in cyclic voltammetry increases after each scan of the potential between −0.1 and 1.3 V for FTO electrode covered with a film of agarose gel in 0.1 M iron sulfate solution. The hematite samples with different thicknesses were prepared using template electrodeposition and annealing in air. The obtained nanostructured films were characterized by field emission scanning electron microscopy, X-ray diffraction, UV–vis spectroscopy, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. The results show that a synergistic improvement of photocurrent density (1.14 mAcm−2 at 1.23 V vs RHE) is induced by Sn-doping and slight surface modification of hematite with thin and discontinuous NiO film. The results indicate that thicker hematite films and hematite films strongly modified with NiO nanostructures show a reduced photoactivity.

Dual Modulated Lateral Photoresistance Effect Observed on Silicon‐Based Discontinuous Copper Film

AbstractA dual modulated lateral photoresistance effect is observed on silicon‐based discontinuous copper film. Through the spatial movement of a laser beam spot, the lateral resistance of the structure can be modulated linearly with polarity under different testing mode. Through applying an electric pulse, the lateral resistance versus laser position curve can be entirely shifted. Carrier diffusion and drift model and charge trap model are set up to explain the dual modulated lateral photoresistance effect. This work adds functionality to Cu materials and is useful for the development of laser‐ and pulse‐modulated photoelectric resistors, switches, and sensors.

Effect of Sn on the oxide subscale structure formed on a 3% Si steel

Addition of tin in 3% Si steel is a method to improve magnetic properties since tin in steel is known as an element that segregates at grain boundaries, inhibits grain growth and has a dragging effect on grain boundary movement. However, tin is generally known as an element that has a harmful effect on surface coating properties. The oxide subscale formed on the decarburization annealing of a 3% Si steel containing tin was investigated by SEM, EDS, GDS and FTIR. The forsterite film was evaluated by SEM, EDS and GDS. The higher tin content decreased thickness, oxygen and fayalite/silica ratio in the subscale and resulted into a discontinuous forsterite film with poor oxidation resistance. After secondary coating the samples presented a reddish color due to the formation of iron oxide and poor dielectric property.

Engineering Silicon to Porous Silicon and Silicon Nanowires by Metal-Assisted Chemical Etching: Role of Ag Size and Electron-Scavenging Rate on Morphology Control and Mechanism.

We demonstrate controlled fabrication of porous Si (PS) and vertically aligned silicon nanowires array starting from bulk silicon wafer by simple chemical etching method, and the underlying mechanism of nanostructure formation is presented. Silicon-oxidation rate and the electron-scavenging rate from metal catalysis play a vital role in determining the morphology of Si nanostructures. The size of Ag catalyst is found to influence the Si oxidation rate. Tunable morphologies from irregular porous to regular nanowire structure could be tailored by controlling the size of Ag nanoparticles and H2O2 concentration. Ag nanoparticles of size around 30 nm resulted in irregular porous structures, whereas discontinuous Ag film yielded nanowire structures. The depth of the porous Si structures and the aspect ratio of Si nanowires depend on H2O2 concentration. For a fixed etching time, the depth of the porous structures increases on increasing the H2O2 concentration. By varying the H2O2 concentration, the surface porosity and aspect ratio of the nanowires were controlled. Controlling the Ag catalyst size critically affects the morphology of the etched Si nanostructures. H2O2 concentration decides the degree of porosity of porous silicon, dimensions and surface porosity of silicon nanowires, and etch depth. The mechanisms of the size- and H2O2-concentration-dependent dissociation of Ag and the formation of porous silicon and silicon nanowire are described in detail.

A New Insight into the Pressure‐Decreasing Mechanism of Hydrophobic Silica Nanoparticles Modified byn‐Propyltrichlorosilane

AbstractHydrophobic silica nanoparticles were prepared for pressure decreasing in water injection through modification of hydrophilic silica nanoparticles byn‐propyltrichlorosilane. Fourier transform infrared spectroscopy analysis and surface hydroxyl number measurement results certified that the modification was very successful. The core flowing experiment showed that the modified hydrophobic silica nanoparticles have an excellent pressure‐decreasing ability. The contact angles measurement results showed that the core chip changed from strong water wet to neutral wet after treated by the modified silica nanoparticles. In this work, a roughness decreasing mechanism is proposed to explain the pressure‐decreasing mechanism of modified silica nanoparticles. After injection into the core, the modified silica nanoparticles occupied the spaces between the sand grains, forming a discontinuous hydrophobic film on the flowing channel surface. This can not only partially change the wettability of the sand surface, but also decrease the roughness of the core flowing channel, decreasing the critical layer thickness and flowing pressure accordingly.