Final Film Thickness Research Articles

Growth kinetics of copper sulfide thin films by photochemical deposition

In this work, copper sulfide (CuxS) thin films were deposited by photochemical deposition (PCD). Although deposition of CuxS thin films via PCD undergoes both heterogeneous and homogeneous reactions, we were able to determine the process conditions that will promote the heterogeneous surface reaction on the surface of the substrate. COMSOL numerical simulations and MATLAB were used to estimate the final CuS film thickness and the process kinetics based on experimental results under multiple operating conditions. Successful kinetic modeling and parameter estimations were performed by adjusting the parameters of mass transport equations that controlled the proposed reaction mechanism of CuS. Therefore, this model can be used as a tool for kinetic parameter estimation and optimization of metal chalcogenide thin films in a PCD system.

Study of electrospray assisted electrophoretic deposition of carbon nanotubes on insulator substrates

In recent years, electrophoretic deposition (EPD) has been adopted as a cost-effective and reliable single-step solution-based room temperature coating method for carbon nanotubes (CNTs), predominantly on conducting surfaces. Contrary to this general pre-requisite of conductive target substrates, in this work we have explored a fabrication strategy for the scalable deposition of CNTs on insulating glass surfaces by the sequential combination of electrospraying and the EPD technique. This combined process flow has been referred to as “electrospray-assisted EPD”, where an initial CNT coating on glass substrates is obtained by electrospraying which, in turn, further assists CNT film growth by EPD. The successful integration of the electrospray technique in the EPD process flow also eliminates the need for surface functionalization of the insulator substrates prior to the deposition step. Electrospray-assisted EPD has resulted in the successful fabrication of uniform, homogenous, and thick CNT deposits (∼4.5 - 5 μm) with precise thickness control. A detailed investigation of the effect of the initial electrosprayed coating on the final CNT film growth and thickness is also presented in this report. This research endeavor presents a significant opportunity for the integration of this deposition model into a wider platform of materials research and technology, chemical sensing, and applications based upon printable and flexible electronics.

Stochastic nonlinear model predictive control applied to a thin film deposition process under uncertainty

This paper investigates the application of stochastic nonlinear model predictive control (NMPC) to a thin film deposition process in the presence of model-plant mismatch while ensuring constraints at a specific probability limit. To capture the multiscale nature of the process, the evolution of the thin film is modelled using nonlinear partial differential equations (PDEs) embedded with lattice-based kinetic Monte Carlo (KMC) simulations. To provide a computationally tractable closed-form expression for online predictive control applications, model identification is performed using data collected from the multiscale deposition model. The closed-form model predicts the expected value and the variance of the thin film properties based on the substrate temperature during the deposition process. The parameters of the closed-form model are determined offline employing power series expansion (PSE). The closed-form model allows the reformulation of probabilistic constraints into their corresponding deterministic expressions thus enabling the design of a computationally tractable stochastic NMPC. To show the effectiveness of the approach, a shrinking horizon stochastic NMPC framework is devised to minimize the final surface roughness while complying with actuator constraints and a probabilistic constraint on the final film thickness.

Fabrication of a Au–polystyrene sphere substrate with three-dimensional nanofeatures for surface-enhanced Raman spectroscopy

Methods for fabricating three-dimensional nanofeature arrays for surface-enhanced Raman spectroscopy (SERS) substrates were explored by combining the self-assembly of nanoscale polystyrene (PS) spheres with subsequent Au film ion sputter coating modulation. The substrate's nanoscale hot-spot features were controlled using the Au coating film thickness regulation and focused ion beam (FIB) nano-patterning regulation methods. Scanning electron microscopy and Raman spectroscopy were employed to analyze the substrate morphology and the enhancement mechanism of the three-dimensional SERS substrate. PS microspheres with diameters of 151nm and 360nm were coated with Au layers of different thicknesses ranging from 10nm to 270nm. The configuration of the Au–PS spheres can be regulated to hexagonal close packing with nanoscale V-shaped slits with a 10–20nm gap pattern. Nanoscale Au particles and clusters with a clear outline covered the surface of the PS spheres, in which the multiple-scale structures increase the specific surface area of the SERS-active substrate. Nanoscale cracks formed on the smaller Au–PS spheres with a diameter of 151nm, which also exhibited strong SERS activity. The substrate surface temperature regularly increased after Au coating, and the thermal expansion coefficient difference and PS glass transition properties were studied to explain the Au–PS spheres nanofeature configuration development. The fabricated Au–PS spheres SERS feature is a type of three-dimensional and highly ordered array, which can show Raman scattering characteristics by providing a SERS enhancement factor of greater than 107.

Numerical simulation of the dip-coating process with wall effects on the coating film thickness

The dip-coating process for liquid film deposition on cylindrical substrates is numerically simulated, and the effects of the coating bath walls proximity to the substrate are investigated for the deposited film thickness. In the present work, the hydrodynamics of non-Newtonian liquid films are studied, applying Carreau and power law models. The free surface position is determined by the volume of fluid technique in a three-dimensional system, while the impacts of density, viscosity, and surface tension are taken into account. The momentum and mass balance, alongside the constitutive equations, were solved for dip-coating process using numerical simulations in an open source CFD software package of OpenFOAM. Numerical outcomes are validated with experimental data over a large range of withdrawal velocities up to 6 m/s. Also good agreement is obtained for numerical simulation results with experimental data for coating thickness, considering the proximity effects of bath walls to the cylindrical substrate being withdrawn from a coating bath.

Factors Affecting on the Electricity Properties of a Metal/Pet Composite during Tensile Deformation

The effects of different factors on the electrical properties of a well-bonded metal/PET composite during tensile deformation were systematically analyzed, including metal materials, metal coating film thickness and environmental temperature. It was found that, before a crack appearance in the coated metal film, the critical elongation of a well-bonded metal/PET composite depended on the differences of modulus and Poisson's ratio between the coated metal material and PET substrate. After cracking, the metal/PET composites with different metal films showed different elongations when there was a sudden increase in the resistance of the metal/PET composite; the thicker the metal film deposited on PET substrate was, the lower resistance the metal/PET composite had. The thickness of metal film had no obvious effect on the critical elongation of the metal/PET composites. In addition, the resistance of the metal/PET composite increased with the increasing environmental temperature.

Large-area synthesis of WSe2 from WO3 by selenium–oxygen ion exchange

Few-layer tungsten diselenide (WSe2) is attractive as a next-generation electronic material as it exhibits modest carrier mobilities and energy band gap in the visible spectra, making it appealing for photovoltaic and low-powered electronic applications. Here we demonstrate the scalable synthesis of large-area, few-layer WSe2 via replacement of oxygen in hexagonally stabilized tungsten oxide films using dimethyl selenium. Cross-sectional transmission electron microscopy reveals successful control of the final WSe2 film thickness through control of initial tungsten oxide thickness, as well as development of layered films with grain sizes up to several hundred nanometers. Raman spectroscopy and atomic force microscopy confirms high crystal uniformity of the converted WSe2, and time domain thermo-reflectance provide evidence that near record low thermal conductivity is achievable in ultra-thin WSe2 using this method.

OS1507 金属被覆により生じるナノワイヤの曲げ変形に関する理論解析

In this study, we discussed about the effect of film thickness on bending deformation of coated nanowire (NW). The three dimensional theoretical model for analyzing the effect was proposed in this paper. The dependence of the misfit strain on the film thickness was introduced in the model. We concluded that bending direction of the NW varied with increasing the coating film thickness. This result arises from the dependence of the misfit strain on the film thickness and the nonuniform film thickness along the circumference of the NW.

同時多層リバースコーティングにおけるロール間流動状態の可視化

Reverse roll coating in which a thin single layer of liquid is applied onto a substrate has been used in industry for decades and has been extensively analyzed in the literature. Modern coatings, however, are often composed of more than one layer to improve product performance and to reduce manufacturing cost. Pre-metered methods such as slot, slide and curtain coating are typically used to produce such multilayer coatings. If the caliper of the substrate to be coated is not constant, the coating gap and consequently the final film thickness deposited on the web will also be non-uniform. In this study we focused on the use of reverse roll technique with slot die liquid delivery system to produce a uniform thin two-layer coating. The use of this coating technique to produce such a coating has not been previously explored. The liquid film surface as it is transferred from a rigid steel roll to a deformable urethane covered roll was visualized in order to find out how the uniformity of two layer coating is affected by the speed ratio between two rolls, layers wet thickness and liquid viscosities. The effect of these parameters on the ribbing frequency and amplitude was also investigated.The results show that in two layer coating, as in the single layer reverse transfer, there is a critical web speed above which ribbing occurs. The critical speed is determined by the bottom layer viscosity.

Modified-release capsules containing sodium riboflavin 5′-phosphate

Introduction: The focus of this work was to produce delayed-release capsules containing riboflavin (vitamin B2, as API) layered pellets. Riboflavin therapy is indicated in patients with a riboflavin deficiency, which usually occurs in conjunction with malabsorption, alcoholism or a protein-calorie deficiency and rarely as the sole vitamin deficiency. Riboflavin is readily absorbed from the upper gastrointestinal tract by a specific transport mechanism. The dissolution rate of coated capsules was controlled through the coating of the capsules and the thickness of the coating layer.Methods: The core pellets (Cellet 300) were loaded with a 10% aqueous solution of sodium riboflavin 5′-phosphate by a layering technique in a coating pan. Hard capsules were filled with riboflavin layered pellets and coated with Eudragit NE polymer with different coating layer thicknesses. The dissolution was tested in gastric and intestinal fluids with the half-change method. The dissolution profiles were analyzed with the use of different mathematical models and an attempt was made to predict the optimum coating film thickness that ensures the required degree and rate of dissolution.Results: A new solid dosage form was developed which can enhance the bioavailability of riboflavin. RRSBW distribution and the Chapman–Richards growth function were used to fit the dissolution profiles. Statistical analysis indicated that the best products were described by the Chapman–Richards equation. The results were utilized to create a theoretical model suitable for prediction of the optimum film thickness that ensures the required release of riboflavin.

Study of Real-Time Measurement for Thickness of Coating Film Based on Quartz Crystal Oscillator

After the technologies of measurement for thin-film thickness were analyzed, the method of real-time measurement for coating thickness based on quartz crystal oscillation was proposed. The principle of the thickness measured by frequency shifting was analyzed on theory, the functional relationship between the resonant frequency shifting and the film thickness changing was deduced. Aim at the complicated working condition in coating machine, the structure of the measuring system for reducing the influence from external pressure and temperature was designed. The circuit for detecting the frequency shift was designed. Final, according to the experiment result, the resolution of thickness measurement can achieve sub-micrometer level.

Electroless Ni-P-C<sub>g</sub>(Graphite)-SiC Composite Coating on Cast AlSi Alloy

The study presents the electroless N-P-Cg-SiC composite coating on cast AlSi (ADC12) alloy where the bath temperature is maintained at 90°C, pH level is controlled between 4.5 to 5.0 and stirred at 450 rpm with mechanical stirrer to avoid particles sedimentation. The increase of the coating film thickness is very insignificant after one hour of coating duration. This outcome is supposed to be due to inconsistent chemical concentration in the plating bath after this period. The nominal coating thickness of 39 μm is achieved after the substrate is immersed for 1 hour in four consecutive plating baths, respectively. The coating film is also successfully adhered to the substrate surface with the SiC and Cgparticles are homogenously distributed.

Drying morphologies and emport rate effect on wetting and spreading behaviours

The main idea of this work is to study the different phenomena of spreading, evaporation, and diffusion that bound to the ink-jet printing. The coating film is studied as well as its drying morphologies and its wetting behavior. Then the drop water spreading on coated fabric is investigated. At that time spreading kinetic is characterized by the digidrop 3S which permits to measure precisely the various parameters such as contact angle, diameter, height, volume and drop profile in contact with the support during wetting phenomenon. This survey shows, on the one hand, that the coating film structure is deeply affected by drying morphologies. On the other hand, drying conditions influence different parameters of kinetic drop spreading on virgin glass and cotton material. Then the increasing of coating film thickness encourages the drop spreading.

Time-resolved light scattering studies of Spin-coated titanium dioxide

Spin coating of titanium alkoxides is a fast and straightforward method of forming compact and durable titanium dioxide thin films. In this report, an optical interference technique is used to understand the dynamics of titanium dioxide thin film formation during the spin coating process of titanium (IV) ethoxide sols, and a 4-stage thinning model is proposed. Optical monitoring of interference fringes as a function of time enables determination of the time-dependent film thickness through measurement of the interference fringe separation while the sol to gel transition can be monitored by analyzing the fringe visibility. For films that are spun at 2,000 rpm or faster, a spin duration of 5 s is sufficient for the film to reach its final thickness. At a given spin speed, spin times longer than 5 s do not affect the final film thickness. However, thinner final film thicknesses can be achieved by increasing the spin speed. All films were found to densify on annealing with an annealed thickness approximately 0.4 times that of the pre-anneal thickness regardless of spin speed. Spin-coated titanium dioxide films are expected to play an important role in low-cost and scalable next generation solar cells employing dyes and quantum dots as the light harvesting agents.

Wafer-Level Integration of High-Quality Bulk Piezoelectric Ceramics on Silicon

In this paper, we present a new post-CMOS-compatible piezoelectric thin/thick film technology that allows wafer-level integration of bulk piezoelectric ceramics such as lead zirconium titanate (PZT) and lead magnesium niobate-lead titanate (PMN-PT) on silicon substrates with precisely determined final film thickness of 5-100 μm while preserving the original material quality. We bond commercially available bulk piezoelectric substrates to silicon using reliable and low-temperature (200°C) gold-indium (Au-In) diffusion bonding or parylene bonding. An enhanced fixed-abrasive lapping/polishing process thins the piezoelectric layer to the desired thickness with high precision and wafer-level uniformity (±0.5 μm). The fabricated films have bond interface shear strength of 1.5-4.5 MPa and average surface roughness of 43 nm, with bulk ferroelectric/piezoelectric properties preserved, such as remnant polarization (37.7 μC/cm2), coercive field (1.95 kV/mm), and effective longitudinal piezoelectric strain coefficients (140-840 pm/V). In addition, extensions of this process show the feasibility of fabricating bimorph layers via successive bonding/thinning, and of forming suspended structures on silicon via surface micromachining. The flexible process can easily be adapted for batch-mode silicon integration of a variety of other electroceramics.

The effects of solvents on the properties of ultra-thin poly (methyl methacrylate) films prepared by spin coating

Poly (methyl methacrylate) (PMMA) is extensively used as an insulating layer in organic electronic devices. In this study, spin coating method was used to cast thin layers of PMMA for dielectric application from solutions in three different solvents, namely dimethylformamide (DMF), n-butyl acetate and toluene. The solvent's vapor pressure causes the solvent to vaporize at different rates leading to layer's distortion and different surface roughnesses. Preparation of suitable surface morphologies, for example, pinhole-free and crack-free was studied. A step profilometer was used to measure the film thicknesses. Alternatively an equation correlating final film thickness to spin speed and solution concentration was proposed. A metal/insulator/metal parallel plate capacitor structure was fabricated and the current density dependence on the applied electric field was measured. The resulting low surface roughness, low leakage currents, high breakdown voltage, and high dielectric constant were obtained for the 100nm-thick PMMA film prepared with DMF.

Inkjet printing of chemically tailored light-emitting polymers

For the implementation of the inkjet printing process in the fabrication of organic devices, like organic light emitting diodes (OLEDs), challenges such as the control over film formation need to be overcome in order to benefit from inkjet printing as a mask-free, material-efficient, non-contact and on-demand patterning technique. In this contribution, three different polymers with tailored properties were synthesized that reveal red, green and blue (RGB) emission colors. Film formation and thin-film properties were investigated in a combinatorial screening approach via inkjet printing. The solvent system toluene/ortho-dichlorobenzene revealed for all three polymers suitable film formation characteristics with final film thicknesses of 80nm using a concentration of 4mg/mL. Important relationships between polymer properties (molar mass), ink characteristics (viscosity) and film formation qualities (thickness, roughness) were identified. Finally, OLED devices were manufactured whereby the light emitting layers were inkjet printed using optimized processing conditions.

High Throughput Selective Epitaxial Growth of In Situ Doped SiCP/SiP Layers for NMOS Devices Using a Si3H8/SiH3CH3/PH3/Cl2 Based Cyclic Deposition and Etch Process

In this paper an efficient deposition process based on Si3H8 (SiH3CH3, and PH3) is combined with a Cl2 based selective chemical vapor etch process. The most efficient and robust processes are isothermal and isobaric, since temperature or pressure changes add processing time, introduce complexity and potential instabilities. Therefore, in order to maximize process efficiency and stability, the aim is to compose isothermal and isobaric process recipes. Deposition profiles and etch profiles are decoupled by clever HW and recipe design and can be tuned independently. [C] concentration and deposition profiles are, to a good approximation, independently optimized, using temperature dependent [C] incorporation and mass flow dominated deposition profile. Important metrics for SiCP epitaxial quality are growth-per-cycle (GPC) and epitaxial etch-to-deposition ratio. Once process temperature and pressure, as well as Si3H8/SiH3CH3/ PH3 deposition gas ratios (determining SiCP alloy composition) are determined, GPC can be adjusted using appropriately chosen (equal) deposition/etch times and the final total film thickness can be targeted by adjusting number of cycles.

Preparation of high-resolution magnetic force microscope tips coated with Co and FeCo films

Magnetic force microscope (MFM) tips are prepared by coating Si tips of 4 nm radius with Co and Fe65 Co35 (at. %) films by employing an ultra-high vacuum evaporation system. The effect of coating film thickness on MFM spatial resolution is investigated. With increasing the thickness from 10 to 20 nm, the resolutions of Co- and FeCo-coated tips improve from 8.4 to 6.9 nm and from 7.5 to 6.6 nm, respectively. Better resolutions are obtained for the FeCo-coated tips, which is due to enhanced sensitivities related with the higher magnetic moment of FeCo material. As the coating thickness further increases, the resolutions deteriorate due to increase of tip radius. The resolution is affected by the detection sensitivity and the tip radius. Magnetic bits of a perpendicular medium recorded at 1800 kFCI (bit length: 14.1 nm) and 1900 kFCI (13.4 nm) are respectively distinguishable in the MFM images observed by using tips coated with Co and FeCo films.

Factors influencing the growth and topography of nanoscale films fabricated by ROMP-mediated continuous assembly of polymers

The continuous assembly of polymers (CAP) mediated via ring-opening metathesis polymerization (ROMP) is demonstrated as a simple and versatile method to fabricate tailored nanostructured thin films. The film thickness and topography were highly dependent upon the variation of different factors that influence the ROMP reaction and mechanism of the assembly process. Herein, we present a detailed investigation of the influence of various parameters on the rate of film formation, the film thickness and the film topography. Whereas the macrocross-linker concentration and molecular weight determined the final film thickness and surface coverage, the initiator concentration and ROMP catalyst activity were found to have a negligible effect on the film properties. Importantly, the minimum amount of polymerizable moieties required in the macrocross-linker to obtain fine control over film thickness and high surface coverage was found to be 7 mol%. The addition of excess ligand (≤100 mM) for the catalyst increased the catalyst lifetime leading to thicker films, although further increases (>100 mM) were found to retard the metathesis reaction. These findings provide valuable insights into the CAPROMP process and will contribute toward developing the next generation of CAP ultrathin films for advanced applications.