Film Thickness Uniformity Research Articles

Investigation of film thickness uniformity in inkjet printing of liquid optically clear adhesive

The inkjet printing process of liquid optically clear adhesive film often leads to the phenomenon of end protrusions, which cause bubbles during subsequent bonding and encapsulation processes or localized Mura defects. To gain a deeper understanding of the mechanism behind the formation of protrusions during film retracts, we derived a dynamic model for the formation of end protrusions in the film. This research also simulated the coalescence of multiple droplets into a film line, including protrusion formation, using the volume of fluid method. The simulation results were compared with theoretical calculations, revealing that the theoretical values were approximately twice as large as the simulated ones. We discovered that the formation of protrusions is the result of the interaction between surface tension and internal forces within the liquid film. During this process, the maximum height of the film line exhibits a positive correlation with the power of time. Finally, the influence of contact angle on the uniformity of film thickness was also explored. It was found that a smaller contact angle can suppress the occurrence of protrusions, leading to a significant improvement in the uniformity of film thickness.

Experimental Investigations on Mechanical Properties of Virgin and Recycled High-Density Polyethylene (HDPE) for the Blown Film Extrusion

Abstract This paper presents an experimental investigation of the mechanical properties when blending virgin and recycled high-density polyethylene (HDPE) for blown film extrusion. The investigation has been made to ensure the films meet or surpass the standards and specifications of commercial HDPE films. A sample with uniform film thickness was produced for both materials before mechanical testing using a universal testing machine. The films were cut into dumbbell shapes in machine and transverse directions, followed by a tensile test of ASTM D638 Type IV standard with a crosshead speed of 50 mm/min and 50 mm gauge length. Results such as tensile strength, elongation at break, and tensile modulus were obtained. The mechanical properties of films made from virgin HDPE and recycled HDPE were compared in various mixture ratios and with those of commercial HDPE film. The results indicate that the mechanical properties of the 8:2 mixture of virgin and recycled HDPE films perform better than the 9:1 or 7:3 mixture, which also outperforms those of commercial HDPE films, with higher tensile strength and elongation at break.

Marangoni-Induced Honeycomb Structures in Spin-Coated Polymer Nanocomposite Films.

This study investigates Marangoni effect-induced structural changes in spin-coated polymer nanocomposite (PNC) films composed of poly(methyl methacrylate)-grafted silica nanoparticles (NPs) and poly(styrene-ran-acrylonitrile). Films cast from methyl isobutyl ketone (MIBK) solvent exhibit distinct hexagonal honeycomb cells with thickness gradients driven by surface tension variations. Atomic force microscopy reveals protruded ridges and junctions at cell intersections, where NP concentration is the highest. Upon annealing at 155 °C, NPs segregate to the surface due to their lower surface energy, and the initially protruding features flatten and eventually form depressed channels while maintaining higher NP density than surrounding areas. Time-of-flight secondary ion mass spectrometry corroborated these findings, highlighting enhanced surface segregation of NPs in MIBK films. These defects can be eliminated using methyl isoamyl ketone (MIAK) as a solvent that produces homogeneous films of uniform thickness. This study highlights the impact of the Marangoni effect on the microstructure and surface properties of PNC films, providing insights for enhancing film quality and performance.

Saturation Mobility of 100 cm2 V-1 s-1 in ZnO Thin-Film Transistors through Quantum Confinement by a Nanoscale In2O3 Interlayer Using Spray Pyrolysis.

In this study, we present a comprehensive study on the fabrication and characterization of heterojunction In2O3/ZnO thin-film transistors (TFTs) aimed at exploiting the quantum confinement effect to enhance device performance. By systematically optimizing the thickness of the crystalline In2O3 (c-In2O3) layer to create a narrow quantum well, we observed a significant increase in saturation mobility (μSAT) from 12.76 to 97.37 cm2 V-1 s-1. This enhancement, attributed to quantum confinement, was achieved through the deposition of a 3 nm c-In2O3 semiconductor via spray pyrolysis. Various In2O3 layer thicknesses (2-5 nm) were obtained by adjusting precursor solution concentration, flow rate, and number of spray cycles. Post annealing treatments were employed to reduce the defects at the interface and within the oxide film, enhancing device stability and performance. Transmission electron microscopy (TEM) confirmed the uniformity of the c-In2O3 film thickness, while variations in thickness significantly influenced TFT performance, particularly the turn-on voltage (VGS) due to changes in the carrier concentration. Ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) supported the formation of a potential well with a two-dimensional electron gas (2DEG). The study of single and multiple superlattice structures of consecutive c-In2O3 and c-ZnO layers provided insights into the effects of multiple quantum wells on the TFT performance. This research presents an advanced approach to TFT optimization, highlighting high reliability, and environmental and bias stabilities. These lead to enhanced mobility and performance uniformity through the precise control of c-In2O3 layer thickness for the quantum confinement effect.

Revealing the dynamics of stagnant rings of third-grade fluid film with heat transfer in the presence of surface tension

In many engineering applications, including coating and lubrication operations, analyzing the temperature behavior of thin film flows on a vertically upward-moving tube is crucial to improving predictive models. This paper examines a steady third-grade fluid film flow with a surface tension gradient on a vertical tube. The mechanisms responsible for the fluid motion are upward tube motion, gravity, and surface tension gradient. This analysis focuses on heat transfer and stagnant ring dynamics. The formulated highly nonlinear ordinary differential equations are solved using the Adomian decomposition method. The conditions for stagnant rings and uniform film thickness are attained and discussed. The inverse capillary number C, Stokes number St, Deborah number De, and Brinkman number Br emerged as flow control parameters. The temperature of the fluid film rises with an increase in the C, St, De, and Br, whereas it decreases with an increase in thermal diffusion rate. The radius of stagnant rings tends to shrink by the increase in C, St, and De. When the value of De is high, third-grade fluid behaves like solids; only free drainage happens with smaller radius stagnant rings and high temperatures. A comparison between Newtonian and third-grade fluids regarding surface tension, velocity, temperature, stationary rings, and fluid film thickness is also provided.

Capacitance-Voltage Fluctuation of SixNy-Based Metal-Insulator-Metal Capacitor Due to Silane Surface Treatment.

In this study, we analyze metal-insulator-metal (MIM) capacitors with different thicknesses of SixNy film (650 Å, 500 Å, and 400 Å) and varying levels of film quality to improve their capacitance density. SixNy thicknesses of 650 Å, 500 Å, and 400 Å are used with four different conditions, designated as MIM (N content 1.49), NEWMIM (N content 28.1), DAMANIT (N content 1.43), and NIT (N content 0.30). We divide the C-V characteristics into two categories: voltage coefficient of capacitance (VCC) and temperature coefficient of capacitance (TCC). There was an overall increase in the VCC as the thickness of the SixNy film decreased, with some variation depending on the condition. However, the TCC did not vary significantly with thickness, only with condition. At the same thickness, the NIT condition yielded the highest capacitance density, while the MIM condition showed the lowest capacitance density. This difference was due to the actual thickness of the film and the variation in its k-value depending on the condition. The most influential factor for capacitance uniformity was the thickness uniformity of the SixNy film.

Multiobjective Optimization Strategy for Enhancing the Efficiency and Quality of Organic Thin-Film Manufacturing with Electrohydrodynamic Atomization Coating.

Electrohydrodynamic atomization coating technology is well-suited for micro-/nanoscale thin-film additive manufacturing. However, there are still some challenges in quality control and parameter adjustment during the coating process. Especially when coating on nonconductive and nonhydrophilic substrates, film quality and thickness uniformity are difficult to control. This paper proposes an optimization strategy for enhancing the efficiency and quality of thin-film manufacturing on nonconductive, nonhydrophilic glass substrates. In this paper, a visual inspection system was developed for in situ inspection and identification of droplet deposition states in the substrate surface. Then, the statistical relationship between the operating parameters and the quality of the deposition state was analyzed by response surface methodology. On this basis, machine learning models and intelligent recommendation frameworks for small data sets were developed to rapidly optimize operating parameters and improve the quality of thin-film coating. Optimization strategy developed by applying the principles of statistical modeling, analysis of variance, and global optimization are more efficient and less costly than traditional parameter screening methods. The experimental results show that optimum deposition quality can be obtained with the recommended operating parameters. And, validation results show a 12.8% improvement in film thickness uniformity. At the same time, no mura defects appeared on the thin-film surface. The proposed optimization strategy can improve the efficiency and quality of additive manufacturing of micro and nano thin films and is beneficial for advancing industrial applications of the electrohydrodynamic atomization coating.

Polycrystalline methylammonium-lead bromide perovskite films for photonic metasurfaces

Polycrystalline films of organo-inorganic perovskite semiconductors are promising as a foundation for creating functional optical metasurfaces. The requirements for film structural perfection, thickness uniformity, and defect-free characteristics are much more stringent compared to perovskite films for photovoltaics. This work presents the results of searching for optimal conditions for one-step synthesis of lead methylammonium bromide films using centrifugation, and describes the successful fabrication of subwavelength optical gratings from these films through focused ion beam processing. The measured spectra of light transmission through the gratings demonstrated their excellent optical quality and confirmed the possibility of creating semiconductor photon metasurfaces with submicrometer periodicity and high-Q dielectric resonances.

Enhanced mucoadhesive properties of ionically cross-linked thiolated gellan gum films

Localized oral drug delivery offers several advantages for treating various disease conditions. However, drug retention at the disease site within the oral cavity is indeed a significant challenge due to the dynamic oral environment. The present study aimed to develop a mucoadhesive inner layer for a three-layer mucoadhesive bandage suitable for localized oral drug delivery. using gellan gum (GG) biopolymer. Gellan gum (GG) was modified using L-cysteine moieties via carbodiimide chemistry. Subsequently, gellan gum solution at different extents of thiolation was ionically cross-linked using aluminum ammonium sulfate. Thiolated gellan gum films of uniform thickness were prepared using a solvent casting method. The thickness of bare gellan gum film was 0.035 ± 0.0043 mm, whereas the thiolated gellan gum films, GG 1S and GG 2S showed a thickness of 0.0191 ± 0.0011 mm and 0.0188 ± 0.0004 mm respectively. A high work of adhesion was noted for thiolated gellan gum (GG 2S) with a value of 10 N.mm while using porcine buccal mucosa. An average tensile strength of 48.2 ± 2.46 MPa was measured for thiolated gellan gum films irrespective of the extent of thiolation. The high work of adhesion, favorable cytocompatibility, desirable mechanical properties, and free swell capacity in saline confirmed the suitability of ionically cross-linked thiolated gellan gum films as an inner mucoadhesive layer for the mucoadhesive bandage.

Development of an advanced in-line multilayer deposition system at Diamond Light Source.

A state-of-the-art multilayer deposition system with a 4200 mm-long linear substrate translator housed within an ultra-high vacuum chamber has been developed. This instrument is engineered to produce single and multilayer coatings, accommodating mirrors up to 2000 mm in length through the utilization of eight rectangular cathodes. To ensure the quality and reliability of the coatings, the system incorporates various diagnostic tools for in situ thickness uniformity and stress measurement. Furthermore, the system features an annealing process capable of heating up to 700°C within the load-lock chamber. The entire operation, including pump down, deposition and venting processes, is automated through user-friendly software. In addition, all essential log data, power of sputtering source, working pressure and motion positions are automatically stored for comprehensive data analysis. Preliminary commissioning results demonstrate excellent lateral film thickness uniformity, achieving 0.26% along the translation direction over 1500 mm in dynamic mode. The multilayer deposition system is poised for use in fabricating periodic, lateral-graded and depth-graded multilayers, specifically catering to the beamlines for diverse scientific applications at Diamond Light Source.

Stagnant rings and uniform film analysis of Phan-Thien Tanner fluid film flow on a vertically upward moving tube

Analyzing Phan-Thien Tanner fluid film behavior on a vertically upward moving tube can help predictive models in engineering, notably in coating and lubrication operations. This paper provides a theoretical analysis of the dynamics of stagnant rings and uniform Phan-Thien Tanner fluid film adhered to a vertically upward moving tube. Formulated ordinary differential equations are solved to get exact analytic expressions for velocity, flow rate, average velocity, shear stress components, and stagnant rings. Highly nonlinear algebraic equations are solved using Newton's method in MAPLE to find the linear and exponential Phan-Thien Tanner film thicknesses. The uniform film thickness widens with increasing constant tube velocity, while it decreases with increasing Deborah number, Stokes number, and elongation parameter. The analysis delineates that stagnant rings shrink around the tube as the Stokes number, Deborah number, and elongation parameter increase. The minimal Stokes condition for the existence of a realistic stagnant ring is also determined. It has been established that whenever the Stokes number is less than the minimal Stokes condition, stagnant rings do not form. A comparison between the exponential Phan-Thien Tanner, linear Phan-Thien Tanner, upper convected Maxwell, and Newtonian fluids is also provided for stagnant rings and fluid film thickness. Following the application of an efficient approximation on tube geometry, plate geometry is approximated, and the outcomes are consistent with existing literature. The results of this research are significant for a wide range of biofluid applications, including agrochemical uses, paint and surface coating flow behavior, thin films on the cornea and lungs, and chemical and nuclear reactor design.

Wafer-scale fabrication of single-crystalline calcium fluoride thin-film on insulator by ion-cutting

Developing bulk materials into thin-films not only enables multiple physical fields to interact strongly within a smaller volume but also enhances the stability, scalability, and integrability of the system. This transformation has been witnessed to lead to significant improvements in the performance of devices utilizing diverse materials across various fields. Calcium Fluoride (CaF2), with remarkable optical properties such as ultralow optical loss and strong nonlinear features, is a preferable material for building ultra-high-Q resonators and stimulating light-matter interaction with low threshold. However, the integration of CaF2 material has remained elusive due to its low hardness and high thermal expansion, which plagues the large-scale fabrication of CaF2 thin film. Here, an optimized ion-cutting technique is proposed for engineering CaF2 thin films theoretically and experimentally. Taking the thermal expansion into consideration, we employ the Lithium niobate (LN) as substrate, and utilize accessible ion implantation, wafer bonding and precisely designed annealing process to attain the CaF2-LN and the CaF2-on-insulator (CaFOI) with high film thickness uniformity and maintained crystalline quality. The perspectives of our work are also illustrated by numerical simulation for further verifying the potential of integrated photonic applications, which could be extended to monolithic optical network by means of large-scale manufacturing method.

The Impact of Microwave Annealing on MoS2 Devices Assisted by Neural Network-Based Big Data Analysis.

Microwave annealing, an emerging annealing method known for its efficiency and low thermal budget, has established a foundational research base in the annealing of molybdenum disulfide (MoS2) devices. Typically, to obtain high-quality MoS2 devices, mechanical exfoliation is commonly employed. This method's challenge lies in achieving uniform film thickness, which limits the use of extensive data for studying the effects of microwave annealing on the MoS2 devices. In this experiment, we utilized a neural network approach based on the HSV (hue, saturation, value) color space to assist in distinguishing film thickness for the fabrication of numerous MoS2 devices with enhanced uniformity and consistency. This method allowed us to precisely assess the impact of microwave annealing on device performance. We discovered a relationship between the device's electrical performance and the annealing power. By analyzing the statistical data of these electrical parameters, we identified the optimal annealing power for MoS2 devices as 700 W, providing insights and guidance for the microwave annealing process of two-dimensional materials.

Research on Film Formation Characteristics by Spraying on Unidiameter Vertical Interpenetrating Cylindrical Surfaces

Unidiameter Vertical Interpenetrating Cylindrical Surfaces (UVICS, also called T-pipe surfaces) are a type of typical complex surface that exists in facilities or equipment such as oil storage tanks and industrial pipelines. The shape and surface characteristics of a component undergoing spraying will have a significant impact on the spray flow field and the resulting coating film. In order to optimize the coating effects of complex surfaces, the Euler-Euler approach was utilized to model a spray film formation process that encompasses both a spray flow field model and a wall adhesion model. Subsequently, the influence of the geometric features, geometric dimensions, lateral air pressure of the spray gun, and spraying distance on the coating film characteristics of this kind of surface were systematically investigated. It is determined that the film thickness uniformity could be enhanced by decreasing the dimensions of the workpiece or increasing the lateral air pressure and spraying distance in an appropriate manner when spraying at the location with the most complex geometric features of UVICS. Furthermore, the optimal parameters under varying spraying conditions were identified. The experiments validated the accuracy of the numerical simulation results and demonstrated the feasibility of this simulation model. The study is of significant value in addressing the challenges associated with film formation during spraying on complex surfaces, developing a comprehensive theoretical framework for air spraying, and expanding the scope of applications for automatic spraying technology.

The development of low-cost spin coater with wireless IoT control for thin film deposition

A low-cost spin coater with a wireless remote system that can deposit thin films of uniform thickness and quality at a significantly lower cost than traditional methods. The system consists of three main parts, a motorized spindle, a spin-coating head, and a control system connected to the network. The mechanical design on the mechanical part, spin coater system design with ESP32, and implementation of wireless control through visual basic. The network-enabled control system allows for real-time monitoring and adjustment of the deposition process, which can improve efficiency and reproducibility. This low-cost spin coating system represents a promising solution for organizations seeking to access thin film deposition technology at a fraction of the cost of traditional systems. By integrating wireless IoT control into low-cost spin coaters, the impact of this technology on coating uniformity will provide valuable insights for future advancements in this field.

Effect of gas pre-decomposition device on the growth of GaN epitaxial layer

In previous studies, the influence of gas phase and surface reactions on the growth of GaN was mainly calculated through simulations. In this study, a novel gas pre-decomposition device (GPDD) was designed to experimentally investigate the effects of gas phase and surface reactions on GaN growth by changing the length and height of the isolation plates (IPs). By varying the structure of the GPDD, the effects on the growth rate and thickness uniformity of the GaN films were studied. The growth rate of the GaN sample slowed with the extension of the IPs because the longer partition plates led to insufficient gas mixing and premature consumption of the precursor trimethylgallium (TMG). The use of GPDD simultaneously achieves high crystal quality and smooth surface morphology of the GaN film. Owing to the use of GPDD, the decomposition of TMG in the pyrolysis pathway was promoted, which suppressed Ga vacancies and C impurities, resulting in weak yellow luminescence bands in the photoluminescence. This study provides a comprehensive understanding of the chemical reaction mechanism of GaN and plays an important role in promoting the development of metal-organic chemical vapor deposition equipment.

Falling film hydrodynamics and heat transfer under vapor shearing from various orientations

Vapor shearing is a common issue encountered in the operations of falling film heat exchangers. The vapor stream effect depends on its orientation. This study investigates liquid film hydrodynamics and heat transfer performance under the influence of vapor streams from different orientations. The results indicate that both orientation and velocity of vapor determine the encountering time and position of the films on the tube's two sides. The liquid film thickness uniformity and the liquid column deflection vary significantly depending on the orientation and velocity of the vapor. Zones of accelerated liquid film, climbing liquid film, liquid stagnation, and transition of liquid film flow pattern are observed. The gradient of film thickness along the tube axis and the deflection in time-averaged peripheral film thickness increase as the vapor orientation varies from 0° to 90° and subsequently decrease as the vapor orientation varies from 90° to 180°. Vapor streams have more pronounced effects on time-averaged peripheral film thickness in regions close to the liquid inlet and outlet. Vapor streams result in changes in peripheral heat transfer coefficients toward the downstream side depending on the orientation and velocity of the vapor. The impact of vapor streams on the overall heat transfer coefficient does not directly correlate with the velocity of the vapor when maintaining the same orientation.

Photocurrent Enhancement by Copper Incorporation in Chemical-Solution-Synthesized Inorganic Lead Perovskite Thin Films.

Perovskite thin films are at the forefront of highly promising photovoltaic technologies due to their remarkable optoelectronic properties. Herein, we explore a low-cost, reproducible, and industry-scalable methodology to synthesize an all-inorganic CsPbI1.5Br1.5 perovskite thin film with additional incorporation of copper and chloride ions into the lattice structure. The synthesis process involves chemical bath deposition of PbS, followed by a gas-solid iodination reaction to yield PbI2. Subsequently, dip-coating incorporates Cs+, Cu2+, Br-, and Cl- ions into PbI2, and annealing at 270 °C produces perovskite thin films. The results show a large coverage area and a uniform thickness of each perovskite thin film. Comprehensive characterization, including X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and photoluminescence, provides the structural, chemical, and optical properties of the synthesized thin films. To evaluate the practical implications of our methodology, we fabricated photodetectors employing CsPbI1.5Br1.5 and (Cs0.95:Cu0.01)PbI1.5Br1.3Cl0.1 perovskite films. A comparative analysis unequivocally demonstrates a significant increase in photodetector performance when utilizing (Cs0.95:Cu0.01)PbI1.5Br1.3Cl0.1 perovskite films. While our findings quantitatively assess the tangible enhancement in photocurrent, we acknowledge the potential for improvement in device fabrication to enhance the overall performance. This study not only affirms the successful low-cost synthesis of perovskite thin films but also emphasizes the pivotal role of Cu2+ and Cl- ions in enhancing the performance of perovskite-based optoelectronic devices.

Fabrication of pH-Responsive PDPAEMA Thin Film Using a One-Step Environmentally Friendly Plasma Enhanced Chemical Vapor Deposition

In recent years, there has been growing interest in pH-responsive polymers. Polymers with ionizable tertiary amine groups, which have the potential to be used in many critical application areas due to their pKa values, have an important place in pH-responsive polymers. In this study, poly(2-Diisopropyl aminoethyl methacrylate) (PDPAEMA) thin films were coated on various substrates such as glass, fabric, and silicon wafer using a one-step environmentally friendly plasma enhanced chemical vapor deposition (PECVD) method. The effects of typical PECVD plasma processing parameters such as substrate temperature, plasma power, and reactor pressure on the deposition rate were studied. The highest deposition rate was obtained at a substrate temperature of 40 °C, a reactor pressure of 300 mtorr, and a plasma power of 60 W. The apparent activation energy was found to be 17.56 kJ/mol. Based on the results of this study, uniform film thickness and surface roughness were observed in a large area. The PDPAEMA thin film was exposed to successive acid/base cycles. The results showed that the pH sensitivity of the thin film produced by the PECVD method is permanent and reversible.

Enhanced Thickness Uniformity of MoS2 Thin Films on SiO2/Si Substrates via Substrate Pre-Treatment with Oxygen Plasma

Enhanced Thickness Uniformity of MoS2 Thin Films on SiO2/Si Substrates via Substrate Pre-Treatment with Oxygen Plasma