Film Deposition Techniques Research Articles

M-DOPA addition in MAPLE immobilization of lipase for biosensor applications

Matrix Assisted Pulsed Laser Evaporation (MAPLE) is a thin film deposition technique which uses a pulsed laser beam impinging, inside a high vacuum chamber, on a frozen target containing the guest molecules in a volatile matrix to induce fast “evaporation” of the matrix, and ejection of the guest molecules. Lipase, an enzyme acting as a catalyst in hydrolysis of lipids, is widely used in biosensors for detection of triglycerides in blood serum. A key action to this purpose is lipase immobilization on a substrate. In a recent paper, we have shown that MAPLE technique is able to deposit lipase on a substrate in an active form. Here we show that addition to the guest/matrix target of a small amount of m-DOPA (3-(3,4-dihydroxyphenyl)-2-methyl-l-alanine) in order to improve adhesion and protect lipase secondary structure, also allows the lowering the laser pulse energy required for matrix evaporation and therefore the risk of damaging the enzyme.

Improving the performance of ITO/ZnO/P3HT:PCBM/Ag solar cells by tuning the surface roughness of sprayed ZnO

A simple hetero junction with configuration ITO/ZnO/P3HT:PCBM/Ag was fabricated by employing chemical spray pyrolysis technique for ZnO thin film and spin coating technique for polymer film deposition. Both ZnO and polymer deposition was conducted in ordinary atmospheric conditions. Roughness of ZnO layer was observed to be crucial parameter that determines overall performance of the device. Optimization of surface roughness of ZnO layer for better quality of the device was achieved through variation of spray parameters (viz., substrate temperature and spray rate). AFM analysis was effectively used to explore the surface roughness of ZnO layer. Structural, optical and electrical studies were also done for samples prepared at optimized condition. The best device under this study has open circuit voltage of 523mV, short circuit current density of 8.32mA/cm2, fill factor of 37% and efficiency of 1.62%. In order to demonstrate the potential of chemical spray pyrolysis technique for large area deposition, the optimized deposition conditions for small area (0.03cm2) cell were extended for large area device (6.25cm2). Indoor and outdoor measurements were also performed on large area device.

Hybrid Films Deposition for Nanochannel Membranes with Functional Surfaces

Thin film deposition is one of the most significant issues in the fabrication of nano structures. Especially it is difficult to achieve conformal films on high-aspect ratio nanostructures, such as nanochannel membranes. Though there are various thin film deposition techniques, atomic layer deposition (ALD) has attracted due to its extreme surface conformality and excellent thickness controllability. Because ALD is a chemical gas phase thin film deposition method based on sequential and self-saturating surface reactions, it can be used for coating of nano structures with high-aspect ratio. Sputtering process is one of the popular film deposition techniques due to its relative simplicity of process and fast deposition speed. However, film depositions by sputtering technique are less conformal compared to those by ALD, because of ions directionality sputtered by plasma. Therefore it is difficult to form films on the surfaces perpendicular to substrate by sputtering process. However, if ALD and sputtering techniques are combined, hybrid thin films deposition which different films are deposited on selectively different surfaces (eg. surfaces perpendicular and parallel to substrate). In this poster, I will present the results of hybrid films deposition on nanochannel membranes with high-aspect ratio. For different functionalities (hydrophilicity and hydrophobicity) of surfaces, Al2O3 and Pt films were grown on nanochannel membranes. Al2O3 films deposition on the vertical surfaces (inner surfaces of nanochannels) was controlled precisely in nanometer scale by using ALD process. Pt films were formed on horizontal surfaces (outer surfaces of nanochannels) by using DC magnetron sputtering. In addition, I will also present the ionic seperation in NaCl solution using fabricated nanochannel membranes by hybrid deposition process and using electrcal bias on Pt films.

Light Directed Electrophoretic Deposition for Additive Manufacturing: Spatially Localized Deposition Control with Photoconductive Counter Electrodes

Electrophoretic deposition (EPD) has traditionally been viewed as a thin film deposition technique for coating conductive surfaces. Recently, there have been reports of producing functional parts with EPD to near net shape, often containing gradients in material properties normal to the conductive deposition surface. By using reconfigurable electrode systems, a few researchers have gone beyond purely out-of-plane gradients and demonstrated gradients in material properties in the plane of the deposition electrode, a necessary condition for 3D additive manufacturing. In this work, we build upon a previously published technique called light directed electrophoretic deposition (LD-EPD) in which the deposition electrode is photoconductive and can be activated with light, leading to a patterned deposit. Here, we demonstrate that the LD-EPD technique can also lead to patterned deposits on any conductive surface by utilizing the photoconductive electrode as the counter electrode. This eliminates several issues with standard LD-EPD by allowing the potentially expensive photoconductive electrode to be reused, as well as mitigates post-processing material compatibility issues by allowing deposition on any conductive surface. We also detail the results of a finite element simulation of the deposition process in LD-EPD systems that captures key features seen experimentally in the final deposit.

Electroluminescence of Zn2GeO4:Mn through SiC whisker electric field enhancement

Alternating current (AC) electroluminescence of thin film oxide phosphors is well known. However in this work electroluminescence of bulk oxide powder phosphors is achieved. A new type of AC Electroluminescent (ACEL) device has been created and developed by integrating SiC whiskers into a phosphor matrix composed of manganese-activated zinc germanate (Zn2GeO4:Mn2+). The conductive SiC whiskers enhance the average electric field in specific regions of the phosphor such that localized breakdown of the phosphor occurs, thus emitting green light. This field enhancement allows light emission to occur in thick film oxide powder phosphors and is notably the first time that bright and reasonably efficient electroluminescence of zinc germanate has been observed without using expensive thin film deposition techniques. Light emission has been achieved in thick pressed pellets using surface-deposited electrodes and the brightness-voltage characteristics of light emission are shown to be consistent with field emission of carriers from the embedded whiskers.

Low Temperature Synthesis of Sub-micrometer Yttria-doped Barium Zirconate Thin Films by Modified Chemical Solution Deposition Technique

Yttria-doped barium zirconate (BZY) electrolyte films with sub-micrometer thickness were prepared using a modified chemical solution deposition (CSD) technique at very low sintering temperature of 800 °C without sintering aid. Pure perovskite BZY phase without barium carbonate associated with low calcination temperature was successfully obtained with no obvious barium (Ba) evaporation to deviate the stoichiometry composition. This cost effective and scalable method for BYZ as compared to the other reported vacuum-based thin film deposition techniques such as pulsed laser deposition (PLD) or atomic layer deposition (ALD) are potentially applicable in the fabrication of high quality electrolyte for nano-thin film micro solid oxide fuel cells operating at temperature below 500 °C.

Silicon Nitride Thin Films Deposited By Reactive Gas-timing Magnetron Sputtering For Protective Coating Applications

Silicon nitride is a promising alternative to carbon based materials for protective coatings, owing to its compatibility with existing silicon-based microfabrication. The complexity of the fabrication processes and contaminations hamper fine-tuning to obtain desirable coating properties. We have explored the reactive gas-timing rf plasma sputtering technique for silicon nitride thin film deposition as an alternative method to fine-tune the film properties. The gas-timing technique controls the on-off sequence of the sputtering gas (Ar) and the reactive gas (N2) during deposition. We focus this investigation to the effect of the Ar:N2 gas timing ratio (10:0, 10:1, 10:3, 10:5, 10:7 and 10:10) on the composition, the morphology, the corrosion resistance, and the hardness properties of the films, in comparison to the films deposited by conventional reactive sputtering with Ar-N2 gas mixture. These deposited silicon nitride films were characterized by Auger electron spectroscopy, Raman spectroscopy, and atomic force microscopy. The chemical resistance was measured by the electrochemical corrosion test in sulfuric acid, while the hardness properties were obtained by nanoindentation. The results reveal that although the nitrogen content in the films increases only slightly when the N2 timing is prolonged, the corrosive current of the films decreases abruptly. A thin passivating oxidized layer is found to play a major role in the corrosion resistance. In contrast, the hardness properties exhibit a uniform variation with the N2 timing. The gas-timing sequence may induce morphological changes the underlying silicon nitride films. The highest hardness obtained by the gas-timing technique almost doubles that produced by the conventional mixed gas sputtering. Thus the reactive gas-timing technique suggests a new route to selectively control the properties of silicon nitride films with minor modification to existing microfabrication processes. Copyright © 2015 VBRI Press.

Supercritical CO2 reactor for wafer-scale thin film deposition: reactor concept, numerical results, and Cu depositio.

Supercritical fluid chemical deposition, frequently abbreviated SFCD, is a thin film deposition technique that employs supercritical fluids. In this deposition technique, a thin film is synthesized from a precursor dissolved in a fluid, along with a reaction reagent if necessary. This paper proposes a novel wafer-scale tool for SFCD. The reactor has a flat cylindrical interior, and the fluid is supplied at the center of the upper face. A porous plate is placed on the bottom face, at the center of which a small fluid outlet is opened. A wafer is placed directly on the porous plate without a holding device, and the diameter of the porous plate is slightly larger than that of the wafer. This reactor has a minimal interior volume and realizes radial and unidirectional flow over the entire wafer. Furthermore, the in-plane pressure distribution is completely uniform, allowing a uniform flow distribution, which was verified by computational fluid dynamics simulations. Cu films were deposited on a 100mm silica glass wafer using Cu(C9H12O2)2 (Cu(dibm)2) as a precursor. The average thicknesses were 75nm at 185°C and 182nm at 200°C,and the standard deviations were 19nm and 14nm, respectively. Basic film characterization was also performed.

A scalable electrodeposition route to the low-cost, versatile and controllable fabrication of perovskite solar cells

Hybrid organic/inorganic perovskite solar cells (PSCs) have emerged as a highly promising alternative renewable energy source because of their high efficiency and low-cost solution processable manufacturing technology. However, the commonly used spin coating process limits the large-scale manufacturing of perovskite layers for commercialization. Here we report on the development of an electrodeposition technique for fabricating perovskite layers and demonstrate its simplicity, versatility, scalability and roll-to-roll manufacturing compatibility. The key step is the electrodeposition of a PbO2 layer on TiO2 scaffold, which is then subjected to chemical bath conversion to sequentially generate PbI2 and CH3NH3PbI3 perovskite. Clearly demonstrated is the controllability of morphology and optical properties of the CH3NH3PbI3 layer, leading to a higher power conversion efficiency (PCE) reproducibility and a higher average PCE when incorporated into carbon-based PSCs than with the spin coating technique. Remarkably, the cell area of electrodeposited PSCs could be easily scaled up to 4cm2 with an excellent perovskite film uniformity, rendering a PCE gain of 36.3% over the spin-coated counterpart. We further demonstrate the deposition of perovskite layers on complex shape substrates (e.g., stainless steel net), which would be rather difficult or impossible with other competing film deposition techniques. These results establish electrodeposition as a versatile and controllable route toward low-cost and large scalable manufacturing of high efficiency PSCs.

Room Temperature Photoluminescence Characterization of Interface Quality of SiN/SiO2/Si Prepared under Various Deposition Techniques and Conditions

Various types of stacked dielectric films are used in complimentary metal-oxide-semiconductor (CMOS) devices in gates, capacitors and device isolation structures. They are also used as insulating materials between conductors, as inter-metal dielectrics (IMD) and inter-layer dielectrics (ILD). The preparation technique, structure and properties of dielectrics strongly influence the quality of the dielectrics/Si interface. Nominally, similar dielectrics/Si structures, even prepared by the same technique, often show different electrical properties depending on subtle differences in process conditions (hidden variables). Monitoring of physical dimensions and chemical compositions of dielectrics often miss unexpected variations in electrical properties. Non-contact electrical property characterization techniques lack lateral resolution and often results in impairment of the dielectrics/Si interface due to strong external electric fields from the measurement process. Alternative dielectrics/Si interface characterization techniques, which can provide insights into electrical properties without external electric field, would be very useful as a complimentary process and material quality monitoring technique. In this study, we have investigated the effect of SiN film deposition techniques on the interface quality of the resulting SiN/SiO2/Si using spectroscopic room temperature photoluminescence (RTPL) under multiwavelength excitation. The sample preparation procedures are as follows. First, ultra thin (~2.2 nm thick), gate oxide quality, thermal oxide films were grown on 300 mm Si(100) wafers. Nominally 5.0 nm thick SiN films were grown on ~2.0 nm thick SiO2/Si wafers using conventional low pressure chemical vapor deposition (LPCVD) and atomic layer deposition (ALD) under various nitrogen source flow conditions. The film thickness was measured (after SiO2 film deposition) before and after SiN deposition using ellipsometry. Figure 1 (a) and (b) show RTPL spectra measured at the center of seven different SiN/SiO2/Si wafers under 650 nm excitation and showing maximum RTPL intensity under 650 nm and 827 nm excitation. Significantly large RTPL intensity variations were measured among the seven SiN/SiO2/Si wafers. The SiN film deposition conditions have modified the underlying SiO2/Si interface characteristics. Non-contact RTPL measurements are very sensitive to the thin film deposition techniques and conditions. It is effective as a complimentary dielectrics/Si process and interface characterization and monitoring technique. Figure 1

Significant Capacity Improvement and Long Cycle-Life of Lithium-Ion Battery through Thin Film Stabilized Cathode Particles

Lithium-ion batteries (LIBs) have been implemented as a high energy and high power density source in numerous electronic devices, electrical vehicles, and space-crafts. A great deal of research has been carried out to improve the lifetime and capacity of LIBs. Thin film coatings on LIB electrode powders have proven to be an effective way to improve the capacity retention, rate capability, and thermal stability of electrode materials. Atomic layer deposition (ALD), as a thin film deposition technique, has been explored as a viable path to improve the performance of LIBs. However, a trade-off between the species transport (capacity) and protection (lifetime), resulting from the insulating properties of ALD films, is the key challenge in ALD technology. Here, we report a new strategy to overcome this trade-off by coating an ultra-thin conformal conductive ALD film on the surfaces of LiMn2O4 particles. The optimized conductive film coated particles exhibit a significant improvement in capacity and cycling performance compared to uncoated samples at room temperature and 55 °C for long cycling numbers. The initial capacity of the conductive film coated sample shows 24% increment compared to the capacity of the uncoated one, and 96% and 95% of the initial capacity is retained after 1,000 cycles with 1 C rate at room temperature and 55 °C, respectively.

A Systematic Study on Sodium Doped Strontium Silicate for SOFC Application

1. Introduction High temperature (HT) operation at 800 – 1000 °C causes many problems such as the thermal mismatch between membrane electrode assembly (MEA) components, expensive bipolar plates, micro structural changes, inter-diffusions, slow start-up time, decreasing system power density due to heat insulators. In order to overcome this main commercialization obstacle of solid oxide fuel cells (SOFCs), a lot of intermediate temperature (IT) electrolyte materials (Doped ceria, LSGM, ScSZ and so on) which can substitute for conventional YSZ have been proposed. And various thin film deposition techniques (Screen printing, Dip-coating, Magnetron sputtering, Pulsed Laser Deposition, Chemical Vapor Deposition and Atomic Layer Deposition) were applied to this research field. The goal of both types of approaches is minimizing the ionic resistance at decreased temperature. Recently, the sodium doped strontium silicate (Sr1-xNaxSiO3-0.5x) is gathering attentions as a fast ion conductor.[1] And Wei et al. confirmed a good SOFC performance using this electrolyte material at 500 and 600 °C. [2] In this study, we investigated on this promising material to get the optimal fabrication conditions with composition and to minimize several problems on this material. 2. Experimental The starting raw powders of SrCO3 (Sigma-Aldrich 99.9%), Na2CO3 (Alfa Aesar, 99.9%) and SiO2(Alfa Aesar 99.9%) were mixed and ball milled. The Na doping percentages on strontium site were 0 to 100 %. We varied calcination temperature from 600 °C to 1000 °C. After ball milling step, we also varied sintering temperature (800 – 1150 °C) and time (10, 20 and 100 h). Conductivity tests were conducted in the air environment and the furnace was controlled from 400 to 750 °C. Sample pellet was prepared to get the thickness of 1.5 mm using low speed saw. Then, we pasted silver electrodes with current collecting meshes on both sides of pellets and connected wires to electrochemical impedance spectrometer (Solartron 1287 and 1260, UK). The micro structural images were captured using a field emission scanning electron microscope (FESEM, Zeiss Ultra) equipped with an energy dispersive X-ray spectroscopy (EDS) analyzer, respectively. The phase check was done using an X-ray diffractometer (D/max-A, Rigaku, Japan) with CuKα radiation (λ=1.5418 Å). The scan range was 2θ = 10 – 70 °at a rate of 5 ° min-1. From this study, we found out the optimal fabrication conditions (sintering at 900 °C for 10 h) for 45 % sodium doped strontium silicate electrolyte which was known as the best ionic conductor. Moreover, we could guess the origin of this high conductivity was from the amorphous sodium silicate. Reference [1] P. Singh and J. B. Goodenough, J. Am. Chem. Soc., 2013, 135, 10149–10154 [2] T. Wei, P.Singh, Y. Gong, J.B. Goodenough, Y. Huang and K. Huang, Energy Environ. Sci., 2014, 7, 1680-1684 Figure 1

Lithium-Ion Battery Cathodes Coated with Ultra-Thin Conductive Films for Long Cycle Life

Atomic layer deposition (ALD), as a thin film deposition technique, has been explored as a viable path to improve the performance of lithium-ion batteries. However, a trade-off between the species transport (capacity) and protection (lifetime), resulting from the insulating properties of ALD films, is the key challenge in ALD technology. Here we report a breakthrough to overcome this trade-off by coating an ultra-thin conformal conductive film by ALD on the surfaces of LiMn2O4 particles. The particles coated with optimized film thickness exhibit a significant improvement in capacity and cycling performance compared to uncoated and insulating ALD film (e.g., Al2O3 and ZrO2) coated samples both at room temperature and 55 °C for long cycling numbers.

A Flexible Thin Film Technique for Rapid Evaluation of Complex Cathode Materials

Lithium ion battery is a popular storage solution but, despite extensive research, only a handful of chemistries have been successfully commercialized. In this work we present a technique to rapidly investigate composite cathode schemes like the Li-rich chemistry. Various thin film deposition techniques have been used to prepare thin film Li ion batteries [1]. In addition to all solid state batteries, the flexibility of a pulsed laser deposition method allows for a variety of detailed investigations. We had previously evaluated single phase LiNiMnCoO2 (NMC) cathode using a one step deposition process [2]. Recently, cathodes which combine two components are gaining popularity. Manganese based chemistries are especially attractive due to its low cost and environmentally friendly nature. LiMO2-Li2MnO3 is an attractive material with almost twice the capacity, of most commercial materials [3]. Various aspects of its operation like microstructure, electrochemical activity, phase as well as new combinations take time consuming experiments to decipher. Moreover, traditional solution based synthesis techniques, makes it difficult to isolate variables and design cathodes to conduct focused studies. We report several experimental models we synthesized to study aspects like micro-structure, phase and stiochiometry effects of Li-rich cathodes and its components. Pulsed laser deposition is a non-equilibrium technique that uses laser ablation to break down target materials into ionic, atomic and molecular species which is then deposited on the substrate. At high temperatures, we believe this should allow for a thermodynamically favorable phase to form. We employed this concept to design deposition process that should theoretically allow us to fabricate and test both the two phase and single phase models proposed by different researchers. This was achieved by using multiple targets to grow 2-phase cathodes and composite targets to simulate the single phase cathode [4]. To investigate the role of O and Li removal on electrochemical activity and activation of Li2MnO3, we varied O and Li stiochiometry of the cathode during deposition. Unlike acid etching this is done during the cathode synthesis step, allowing additional flexibility. The correlation between composition variation, microstructure and electrochemical behavior was investigated with cathodes deposited using two separate targets of Li2MnO3and NMC. Electrochemical testing showed that an optimum performance was obtained for films with nano-domains of Li2MnO3 in a NMC matrix with a discharge capacity of 290 mAh/g. Li2MnO3 domain size clearly plays an important role in the mechanism that results in the high capacity of the Li-rich chemistry. Oxygen and Li stiochiometry variations in Li2MnO3 showed that an optimum capacity of 225 mAh/g was obtained for cathodes deposited at 50 mtor partial oxygen pressure. Samples with very low Li and O content showed formation of MnO2 phase with lower capacity (115 mAh/g) and distinct absence of any redox peak at 3 V which were seen for samples with higher O and Li content. The effect of composition variation on domain size and electrochemical properties is critical for the performance of the Li-rich cathodes. Thin film based model cathode synthesis approach allowed us to investigate different aspects of the Li-rich cathodes in a rapid and efficient manner. It can also be used to investigate new material schemes in a systematic manner.

Deposition of Ge23Sb7S70 chalcogenide glass films by electrospray

Solution-based chalcogenide glass films, traditionally deposited by spin-coating, are attractive for their potential use in chip-based devices operating in the mid-infrared and for ease of nanostructure incorporation. To overcome limitations of spin-coating such as excessive material waste and difficulty for scale-up, this paper introduces electrospray as a film deposition technique for solution-based chalcogenide glasses. Electrospray is shown to produce Ge23Sb7S70 films with similar surface quality and optical properties as films deposited by spin-coating. The advantages of electrospray deposition for nanoparticle dispersion, scalable and continuous manufacturing with little material waste, and comparable film quality to spin-coating make electrospray a promising deposition method for practical applications of chalcogenide glass films.

Significant Capacity and Cycle‐Life Improvement of Lithium‐Ion Batteries through Ultrathin Conductive Film Stabilized Cathode Particles

Atomic layer deposition (ALD), as a thin film deposition technique, has been explored as a viable path to improve the performance of lithium‐ion batteries. However, a trade‐off between the species transport (capacity) and protection (lifetime), resulting from the insulating properties of ALD films, is the key challenge in ALD technology. Here we report a breakthrough to overcome this trade‐off by coating an ultrathin conformal cerium dioxide (CeO2) film on the surfaces of LiMn2O4 particles. The optimized CeO2 film (≈3 nm) coated particles exhibit a significant improvement in capacity and cycling performance compared to uncoated (UC), Al2O3 coated, and ZrO2 coated samples at room temperature and 55 °C for long cycling numbers. The initial capacity of the 3 nm CeO2‐coated sample shows 24% increment compared to the capacity of the uncoated one, and 96% and 95% of the initial capacity is retained after 1000 cycles with 1C rate at room temperature and 55 °C, respectively. The detailed electrochemical data reveal that the suppression of the impedance rise and the facile transport of the species are the main contributors to the success.

Improved self-assembled thiol stationary phases in microfluidic gas separation columns

Semipacked columns (SPCs) with integrated micropillars have been characterized for high chromatographic efficiencies and fast separations. In this article, high-yield and stable alkane thiol based stationary phase coating methods are presented for SPCs. Briefly, a new three step (anisotropic, O2 plasma, and isotropic) etching method is first developed in order to improve metal lift-off by producing a 3-dimensional undercutting profile inside deep etched SPCs. This innovative fabrication scheme is used for 1m-long, 220μm-deep, 190μm-wide SPCs with circular micropillars of 20μm-diameters and 42μm-post spacing. Two different thin gold film deposition techniques are utilized for microcolumns (1) a wafer-level physical vapor deposition, and (2) a device level layer-by-layer (LbL) self-assembly of gold nanoparticles (3.2nm diameter). After gold film deposition and metal lift-off, the surface of the patterned gold layer is functionalized with a 2mM octadecanethiol (C18H37SH) solution for chromatographic separations. Both kinetic (Golay plots) and thermodynamic (Van’t Hoff plot) properties of thiol-functionalized gold phases are studied. The significance of SPCs, for faster analysis, is also validated by achieving baseline separation of a straight chain alkane mixture, containing high boilers (174°C to 287°C), within 45s.

Effect of CW-CO<sub>2</sub> Laser Evaporation Parameters on Structural and Physical Properties of ZnSe Film

ZnSe thin films were deposited onto glass substrates by CW-CO2 laser evaporation with the various evaporation times and laser power. SEM studies showed that the thicknesses of deposited films were varied from 176 nm to 1824 nm. AFM studies showed that the surface roughnesses were varied from 2.4 nm to 5.1 nm. The structure of deposited films were indicated by XRD technique which the result showed the cubic structure. The average crystallite sizes were calculated from the XRD pattern with ranged between 23.8 nm and 31.7 nm. The transmission spectates were ranged from 250 nm to 900 nm. The values of the optical bandgap energies determined from the absorption spectra were ranged between 2.61 eV and 2.88 eV. This paper presents the simple and low cost technique for ZnSe film deposition. Another advantage of this research is the high-precision control of thickness by the variation of the evaporation time and laser power.

Nanobrick wall multilayer thin films grown faster and stronger using electrophoretic deposition

In an effort to speed up the layer-by-layer (LbL) deposition technique, electrophoretic deposition (EPD) is employed with weak polyelectrolytes and clay nanoplatelets. The introduction of an electric field results in nearly an order of magnitude increase in thickness relative to conventional LbL deposition for a given number of deposited layers. A higher clay concentration also results with the EPD–LbL process, which produces higher modulus and strength with fewer deposited layers. A 20 quadlayer (QL) assembly of linear polyethyleneimine (LPEI)/poly(acrylic acid)/LPEI/clay has an elastic modulus of 45 GPa, tensile strength of 70 MPa, and thickness of 4.4 μm. Traditional LbL requires 40 QL to achieve the same thickness, with lower modulus and strength. This study reveals how these films grow and maintain a highly ordered nanobrick wall structure that is commonly associated with LbL deposition. Fewer layers required to achieve improved properties will open up many new opportunities for this multifunctional thin film deposition technique.

Sensitivity enhancement of OD- and OD-CNT-based humidity sensors by high gravity thin film deposition technique

The humidity sensing properties of the thin films of an organic semiconductor material orange dye (OD) and its composite with CNTs deposited at high gravity conditions have been reported. Impedance, phase angle, capacitance and dissipation of the samples were measured at 1 kHz and room temperature conditions. The impedance decreases and capacitance increases with an increase in the humidity level. It was found that the sensitivity of the OD-based thin film samples deposited at high gravity condition is higher than the samples deposited at low gravity condition. The impedances and capacitance sensitivities of the of the samples deposited under high gravity condition are 6.1 times and 1.6 times higher than the films deposited under low gravity condition.