Good Film Uniformity Research Articles

Fabrication and Characterization of Orodispersible Composite Film from Hydroxypropylmethyl Cellulose-Crosslinked Carboxymethyl Rice Starch.

Crosslinked carboxymethyl rice starch (CLCMRS), prepared via dual modifications of native rice starch (NRS) with chloroacetic acid and sodium trimetaphosphate, was employed to facilitate the disintegration of hydroxypropylmethylcellulose (HPMC) orodispersible films (ODFs), with or without the addition of glycerol. Fabricated by using the solvent casting method, the composite films, with the HPMC--LCMRS ratios of 9:1, 7:1, 5:1 and 4:1, were then subjected to physicochemical and mechanical evaluations, including weight, thickness, moisture content and moisture absorption, swelling index, transparency, folding endurance, scanning electron microscopy, Fourier transform infrared spectroscopy, tensile strength, elongation at break, and Young’s modulus, as well as the determination of disintegration time by using the Petri dish method (PDM) and slide frame and bead method (SFM). The results showed that HPMC-CLCMRS composite films exhibited good film integrity, uniformity, and transparency with up to 20% CLCMRS incorporation (4:1 ratio). Non-plasticized composite films showed no significant changes in the average weight, thickness, density, folding endurance (96–122), tensile strength (2.01–2.13 MPa) and Young’s modulus (10.28–11.59 MPa) compared to HPMC film (135, 2.24 MPa, 10.67 MPa, respectively). On the other hand, the moisture content and moisture absorption were slightly higher, whereas the elongation at break (EAB; 4.31–5.09%) and the transparency (4.73–6.18) were slightly lowered from that of the HPMC film (6.03% and 7.03%, respectively). With the addition of glycerol as a plasticizer, the average weight and film thickness increased, and the density decreased. The folding endurance was improved (to >300), while the transparency remained in the acceptable range. Although the tensile strength of most composite films decreased (0.66–1.75 MPa), they all exhibited improved flexibility (EAB 7.27–11.07%) while retaining structural integrity. The disintegration times of most composite films (PDM 109–331, SFM 70–214 s) were lower than those of HPMC film (PDM 345, SFM 229 s). In conclusion, the incorporation of CLCMRS significantly improved the disintegration time of the composite films whereas it did not affect or only slightly affected the physicochemical and mechanical characteristics of the films. The 5:1 and 4:1 HPMC:CLCMRS composite films, in particular, showed promising potential application as a film base for the manufacturing of orodispersible film dosage forms.

Interfaces and pattern resolution of inkjet-printed organic light-emitting diodes with a novel hole transport layer

In this paper, the effects of the combination of solvents on the uniformity of a dried emitting layer and on device performance were studied. Green emitter inks with various solvents were prepared, and it was seen that good film uniformity of printed layers could be obtained with a solvent mixture with different boiling points, which reduced the coffee ring effect on a dried surface. During the inkjet process, the drop injection condition aiming was also controlled for better drop-to-drop spacing and reduction of the line-edge roughness. Printed patterns of a small molecular/polymer hybrid emitting layer, composed of the chlorobenzene-dichlorobenzene solvent mixture, showed significantly reduced roughness of the microscopic surface and improved efficiency of the inkjet device, at levels nearly comparable to those of spin-coated patterns. A suitable hole transport layer (HTL) was also further developed as an interfacial material, prior to the solution processing of the emitter. The cross-linkable HTL was composed of triphenylamine as the cross-linking unit and a fluorene-based compound. At the optimized condition of the solvent formulation, printed droplets within 100 µm× 300 µm pixels formed a uniform stripe without remarkable coffee-ring defects and line-edge surface roughness.

Influence of precursor dose and residence time on the growth rate and uniformity of vanadium dioxide thin films by atomic layer deposition

The growth of vanadium dioxide (VO2) thin films using tetrakis (ethyl-methyl) amino vanadium (TEMAV) and H2O by atomic layer deposition (ALD) has been investigated as a function of the exposure dose and residence time. A novel multiple pulse mode has been employed to mitigate the small deposition rate brought about by the low vapor pressure of TEMAV. Compared to the conventional ALD cycle with a single pulse of precursor, the use of multiple pulsing with very short pulse time allows lower consumption of precursor, but larger exposure dose and longer residence time on the growth surface, resulting in a higher growth rate for a low volatility precursor, while maintaining a good film uniformity across 4-in. wafers. The Raman analysis and the electrical resistivity modulation of the VO2 thin films show that the films synthesized by the multiple pulse mode is comparable to the films synthesized by the conventional single pulse mode.

Homogeneous dual-gate MoS2 field-effect transistors integrated by atomic layer deposition-based film synthesis

Various synthetic approaches have been proposed and studied to grow high-quality two-dimensional (2D) transition metal dichalcogenides (TMDCs) thin films. However, most of current methods suffer from intrinsic material defects or technical limitations. Here, in this paper, large-area few-layer MoS2 thin films have been prepared on SiO2/Si substrate through sulfurizing pre-deposited MoO3 film by atomic layer deposition (ALD). Good film uniformity, crystallinity and stoichiometry have been successfully achieved. The film thickness can be precisely controlled by adjusting the ALD cycle numbers during MoO3 deposition. Field-effect transistor (FET) arrays have been further fabricated based on the large-area MoS2 film. Both back-gate and top-gate geometries have been applied and have shown excellent reproducibility in electrical performance with average electron mobility of 1.71 cm2 V−1 s−1 and 0.31 cm2 V−1 s−1 for the back-gate and top-gate FETs, respectively. Our results have enabled a promising pathway with such thickness-controlled TMD film and homogeneous FET devices towards future low-dimensional nanoelectronics applications.

Interfacial crosslinked controlled thickness graphene oxide thin-films through dip-assisted layer-by-layer assembly means

The augmentation of research in graphene based thin films has been of great interest to various current industrial stakeholders. This is mainly due to the wide scope of films applications, ranging from nanoelectronics to separation membranes. Therefore, establishing a relation between graphene based thin film key characteristics and the fabrication operating conditions is of high significance. This study entails the successful fabrication of controlled-thickness crosslinked graphene oxide (GO) thin films on inexpensive silicon-based glass slide substrates. The method of film fabrication used is the dip-assisted layer-by-layer assembly, which has an added advantage of step-control of thin film thickness, good film uniformity and continuity. The thickness was primarily tuned through the use different sized crosslinkers; a covalent based sub-nanometer sized p-phenylenediamine and an electrostatic based polyethyleneimine on an interchangeable assembly with GO. Pre film fabrication, Fourier Transform Infra-Red and X-Ray Photoelectron Spectroscopy characterizations were carried out to determine the nature of interactions between GO and the crosslinkers. Post film fabrication, scanning electron microscopy, water contact angle measurements and profilometry analysis were undertaken for film continuity, hydrophilicity and thickness measurements respectively. A strong linear trend between film thickness of the differently crosslinked films and the number of bi-layers was established.

Structural, stoichiometric and optical constants of crystalline undoped lead iodide films prepared by the flash-evaporation method

The flash-evaporation method was used to deposit several thin films (1, 1.2, and 1.35 µm thick) of undoped lead iodide on glass slides held at $$150$$ °C and $$200$$ °C. Their X-ray diffraction patterns, scanning electron microscope micrographs, and energy-dispersive spectroscopy spectra revealed crystalline hexagonal 2H-polytypic structure and high stoichiometry ( $${\text{PbI}}_{x} ;x \cong 1.9$$ ). Their as-measured normal-incidence transmittance $$T_{\text{exp}} (\lambda)$$ –wavelength $$\lambda$$ curves exhibited above a specific wavelength $$\lambda_{{\text{c}}} \approx 520{\text{ nm}}$$ and many well-resolved interference-fringe maxima and minima, indicating good film uniformity. Below $$\lambda_{{\text{c}}}$$ , these $$T_{\text{exp}} (\lambda) - \lambda$$ curves declined sharply toward $$T_{\text{exp}} (\lambda) \cong 0$$ , signifying high film crystallinity. The $$\lambda$$ dependency of optical constants $$n(\lambda)$$ and $$\kappa (\lambda)$$ retrieved from numeric iterative curve fitting of $$T_{\text{exp}} (\lambda) - \lambda$$ data to theoretical $$T_{{{\text{theor}}}} (\lambda)$$ formula describe an air-supported {film/substrate} structure, combined with O’Leary–Johnson–Lim (OJL) interband transition dispersion model and a set of harmonic-like oscillator dispersion formulas. The retrieved bandgap energy $$E_{{\text{g}}}^{{{\text{opt}}}}$$ and band-tail breadth $$\gamma$$ were around $$2.4\,{\text{ eV}}$$ and $$100\,{\text{ meV}}$$ , respectively. The determined $$n(\lambda) - \lambda$$ data gave best curve fits to the Wemple–DiDomenico (WDD) equation with reasonable bandgap energy parameter $$E_{{\text{o}}} \cong 3.8\,{\text{ eV}} \cong 1.6\,E_{{\text{g}}}^{{{\text{opt}}}}$$ , single-oscillator energy strength $$E_{{\text{d}}} \cong 18\,{\text{ eV}}$$ and static index of refraction $$n_{{\text{o}}} \cong 2.4$$ . The calculated optical absorption coefficient $$\alpha (\lambda) = 4{\uppi }\kappa (\lambda)/\lambda$$ was found to obey the direct interband transition with bandgap energy $$E_{{\text{g}}} \cong 2.45\,{\text{ eV}}$$ in the absorption edge region, near which the curve fits of $$\alpha (\lambda)$$ to Urbach formula gave an Urbach tail parameter $${\Gamma }_{{\text{U}}}$$ of $$45\,{\text{ meV}}$$ , consistent with the results of numerical analysis of $$T_{\text{exp}} (\lambda) - \lambda$$ curves. The film thickness and substrate temperature had a slight effect on the determined optical parameters.

Synthesis of large-scale few-layer PtS2 films by chemical vapor deposition

PtS2, a group-10 transition metal dichalcogenide, has prominent layer-depended band structure, and can enable extremely high phonon-limited mobility at room temperature. Here, we demonstrate the theoretical study on the electronic band structures of PtS2 with different thickness by using density functional theory (DFT), as well as experimental realization of large-area synthesis of few-layer PtS2 film by direct sulfurization of pre-deposited Pt. The synthetic process suggested that the reaction pressure is a key factor in the formation of high-quality PtS2 semiconducting films. Characterizations with atomic force microscopy (AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) have indicated that good film stoichiometry and uniformity have been achieved. Furthermore, field-effect transistor (FET) arrays were fabricated based on the large-scale PtS2 film, exhibiting well-uniform electrical performance with p-type transport behavior. These results can open up an attractive approach to promote the large-scale applications of PtS2 in advanced nanoelectronics and optoelectronics devices and systems.

Solution Coating of Small Molecule/Polymer Blends Enabling Ultralow Voltage and High‐Mobility Organic Transistors

AbstractLow‐voltage organic field‐effect transistors (OFETs) are of great interest for organic electronics applications that require low power consumption such as wearable electronics, biomedical applications, or mobile electronics. In this work, an approach leading to transistors fabricated from solution with high charge carrier mobilities operating at voltages < 1 V is presented. By blending the small‐molecule semiconductor 6,13‐bis(triisopropylsilyl‐ethynyl)pentacene (TIPS‐pentacene) with polystyrene it is possible to achieve good film coverage and uniformity as well as ultrathin semiconductor films. This reduction in thickness relative to neat films results in a high fraction of the high‐mobility polymorph of TIPS‐pentacene and excellent film morphologies with continuous highly crystalline domains. OFETs using SiO2 as the dielectric with average hole mobilities as high as 8.3 cm2 V−1 s−1 and maximum mobilities of up to 12.3 cm2 V−1 s−1 which favorably compares with the previous record for TIPS‐pentacene, especially when considering the simplicity of the approach, are demonstrated. By depositing the optimized semiconductor blends on solution‐based polymer dielectric layers of polyvinylphenol, cross‐linked with 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride, a record‐high mobility of 4.2 cm2 V−1 s−1 for solution‐processed, ultralow‐voltage OFET devices (operating at <1 V) is obtained.

PEDOT:PSS-CrO3 composite hole-transporting layer for high-performance p-i-n structure perovskite solar cells

A solution-processed hole-transporting layer for planar perovskite solar cells (PSCs) is developed by simply incorporating the CrO3 aqueous solution into the ploy(3,4-ethylene-dioxythiophene):ploystyrenesulfonate (PEDOT:PSS) aqueous dispersion. Besides the merits of high conductivity and interface modification, PEDOT:PSS-CrO3 composite films can act as a good underlayer for the growth of the crystal perovskite films. The CH3NH3PbI3−xClx film deposited on the PEDOT:PSS-CrO3 underlayer demonstrates high quality with large-scale domains and good film uniformity, which results in obvious improvement of the absorption in almost whole visible-light range. The resulting PSC device shows a power conversion efficiency (PCE) as high as 16.90%.

Preparation and physicochemical evaluation of transdermal aerosols containing ketoprofen

Purpose: To prepare transdermal ketoprofen metered-dose aerosol formulations containing menthol and isopropyl myristate (IPM) as penetration enhancers and to evaluate their physicochemical and permeation properties.Methods: Selected ratios of ketoprofen, ethanol, polyvinylpyrrolidone K30 (PVP K30, anti-nucleant), and penetration enhancers were mixed and filled into aluminum aerosol cans with hydrofluoroalkane- 134a as propellant. The physicochemical properties of the films, and their ex vivo permeation properties in rat skin were investigated over a 24-h period. Rat skin was exposed to a definite dose of each ketoprofen film to determine the quantity of drug in the receptor compartment over a 24-h period.Results: All the transdermal formulations showed good integrity and film uniformity. Formulations with permeation enhancers presented higher rates of skin penetration compared to control formulations. Formulations containing 3% PVP and 5% IPM produced the highest permeation rates (Jss, 85.35 μg/cm2/h).Conclusion: These results indicate that incorporation of antinucleant polymer and permeation enhancers in aerosols containing ketoprofen enhances aerosol stability and drug permeation through rat skin.Keywords: Ketoprofen, Antinucleant, Permeation enhancer, Topical aerosol, Transdermal delivery

The Impact of Reaction Parameters on Graphene-like Material Synthesized Using Chemical Vapour Deposition

The remarkable properties of graphene have directly accelerated the graphene research. Due to its unique and remarkable characteristics, graphene can be potentially used in various applications. Chemical Vapour Deposition (CVD) has been identified as a promising and important method for preparation and production of graphene due to its good film uniformity and large scale production. Herein, we demonstrated that reaction parameters including the reaction duration and reaction temperature could affect the quality, quantity and morphology of synthesized samples. Energy Dispersive X-ray (EDX) results indicated that the carbon content on the graphene-like samples increased with the increasing reaction duration. Scanning electron microscopy (SEM) images showed that thicker carbon clusters were grown when a longer reaction time was used. X-ray diffraction (XRD) pattern indicted carbon existed in the samples synthesized. The comparison between different reaction parameters can assist in selecting the optimum growth parameters of graphene-like samples.

Preparing molybdenum disulphide by vapour deposition

Two-dimensional graphene-like molybdenum disulphide with many unique properties, a relatively new and exciting transition metal dichalcogenide, has been extensively researched. This review discusses preparing molybdenum disulphide by vapour deposition, which has many advantages, including good spreadability, film uniformity and strong bonding forces with the substrate. We also review the compositing, decorating and doping of MoS2 by vapour deposition, and briefly discuss the applications of MoS2 produced by vapour deposition.

Dynamics of the atmospheric pressure diffuse dielectric barrier discharge between cylindrical electrodes in roll-to-roll PECVD reactor

The high current diffuse dielectric barrier discharge (DBD) was operated in a bi-axial cylindrical electrode configuration using nitrogen, oxygen and argon gas flow with the addition of tetraethyl orthosilicate as precursor for silica-like film deposition. The behaviour of the transient plasma was visualized by means of fast imaging from two orthogonal directions. The formation and propagation (~3 × 10 4 m s −1 ) of lateral ionization waves with the transverse light emission structure similar to the low pressure glow discharge was observed at time scales below 1 µ s. Despite plasma non-uniformity at nanosecond time scale the deposition process on the web-rolled polymer results in smooth well adherent films with good film uniformity and excellent gas diffusion barrier properties.

Improved hole interfacial layer for planar perovskite solar cells with efficiency exceeding 15%.

PSS-GeO2 composite films by simply incorporating the GeO2 aqueous solution into the PSS aqueous dispersion as a hole transport layer in planar PSCs. Besides the merits of high conductivity, ambient stability and interface modification of PSS-GeO2 composite films, the formed island-like GeO2 particles are assumed to act as growing sites of crystal nucleus of perovskite films during annealing. By the seed-mediation of GeO2 particles, a superior CH3NH3PbI(3-x)Cl(x) crystalline film with large-scale domains and good film uniformity was obtained. The resulting PSC device with PSS-GeO2 composite film as HTL shows a best performance with 15.15% PCE and a fill factor (FF) of 74%. There is a remarkable improvement (∼37%) in PCE, from 9.87% to 13.54% (in average for over 120 devices), compared with the reference pristine PSS based device.

Geometry optimization in planetary rotation stage for thickness uniformity of films on spherical substrates

We report the simulation results on the thickness uniformity of optical coatings deposited on spherical substrates by optimizing the geometric configuration parameters, such as tilting angle of the substrate holder and position of the evaporation source in a 1 000-mm-diameter planetary rotation stage (PRS). We reveal that good film uniformity on convex spherical surfaces or flat substrates, as well as concave surfaces with weak to moderate curvatures can be obtained through appropriate tilting of the substrate holder. For 300-mm-diameter substrates with clear aperture to radius of curvature (CA/RoC) between -0.3 and 0.7, the achievable film uniformity is above 99%. The source position is optimized to achieve good film uniformity. © 2013 Chinese Optics Letters.

Electrical properties of ferroelectric-gate FETs with SrBi2Ta2O9 formed using MOCVD technique

Ferroelectric-gate field-effect transistors (FeFETs) with a Pt/SrBi2Ta2O9/Hf-Al-O/Si gate stack were fabricated using the metal-organic chemical vapor deposition (MOCVD) technique to prepare the SrBi2Ta2O9 (SBT) ferroelectric layer. A good threshold voltage (V th) distribution was found for more than 90 n-channel FeFETs in one chip with a 170 nm SBT layer owing to the good film uniformity of the SBT layer deposited by MOCVD. The average memory window \((V_{\mathrm{w}}^{\mathrm{av}})\) and the standard deviations (σ thl,σ thr) of the left- and right-side branches of the drain-gate voltage curves of the FeFETs yielded a \(V_{\mathrm{w}}^{\mathrm{av}}/(\sigma_{\mathrm{thl}} + \sigma_{\mathrm{thr}})\) value of 5.45, indicating that the FeFETs can be adapted for large-scale-integration. The electric field, the energy band profile in the gate stack, and the gate leakage current were also investigated at high gate voltages. We found that the effect of Fowler–Nordheim tunneling appeared under these conditions. Because of the tunneling injection and trapping of electrons into the gate insulators, the operation voltage ranges of the FeFETs were limited by this tunneling.

High Molecular Weight PVK as an Interlayer in Green Phosphorescent OLEDs

Performance of high molecular weight polyvinylcarbazole (PVK) (Mn = 1,100,000) as an interlayer has been demonstrated in the green phosphorescent organic light emitting devices (PHOLEDs) using solution process. The PVK interlayer on the surface of PEDOT:PSS has a good film uniformity characteristic with homogenous low dissolution, thereby improving the charge injection in the emissive layer effectively. The performance of high molecular weight PVK interlayer was compared with the poly(2,7-(9,9-di-n-octylfluorene)-alt-(1,4-phenylene-((4-sec-butylphenyl)imino)-1,4-phenylene)) (TFB) interlayer. The maximum current and power efficiency values of 23.1cd/A, 9.8 lm/W were demonstrated using a PVK interlayer in the green PHOLED. The effect of high molecular weight PVK interlayer and the device structure by solution processing are provided with efficient and simple manufacturing.

Synthesis and dielectric properties of photoreactive polystyrene containing [1-(3-isopropenyl-phenyl)-1-methyl-ethyl]-carbamate in the side chain

Novel polystyrene derivatives comprising [1-(3-isopropenyl-phenyl)-1-methyl-ethyl]-carbamate in the side chain were synthesized as photoreactive copolymers. Poly(4-vinylphenol) was made to react with 1-(1-isocyanato-1-methyl-ethyl)-3-isopropenyl-benzene (m-TMI) and the unreacted hydroxyl groups were protected with acetyl chloride. The copolymers are highly sensitive to the radical photoinitiators that can be activated by irradiation of UV light (λ = 300–365 nm). FTIR spectroscopy was employed to monitor the structural changes in the copolymers exposed to UV irradiation. The dielectric properties of the copolymers were investigated by measuring the capacitance and calculating the permittivity as a function of frequency, along with the I–V characteristics. Their properties were compared with those of thermally crosslinkable poly(4-vinylphenol) blended with poly(melamine-co-formaldehyde), which is frequently used as a dielectric layer in organic field-effect transistors (OFETs). No significant dielectric dispersion was observed in the frequency range of 1 kHz–1 MHz. The dielectric constant was determined to be in the range of 4.2–6.0, which offers a potential for the application of these copolymers to OFET gate insulators. These soluble dielectrics exhibit good film uniformity and can also be patterned using a standard photolithographic technique. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1710–1718, 2008

Near-infrared response photovoltaic device based on novel narrow band gap small molecule and PCBM fabricated by solution processing

In this paper, we report on synthesis of a novel diphenylaminofluorenyl-capped thiadiazoloquinoxaline (6,7-dimethyl-4,9-di{5-[9,9-bis(octyl)-7-diphenylaminofluorene-2-yl]-4-hexylthien-2-yl}[1,2,5]-thiadiazolo[3,4- g]quinoxaline (DPAFL-TDOX-DPAFL which is further abbreviated to TDOX), Scheme 1) and its use as donor material for the realization of efficient bulk-heterojunction organic solar cell by spin coating from blend with PCBM as acceptor. TDOX showed very good solution processibility and film uniformity up to weight ratio TDOX:PCBM=1:4. Spectral response was extended to near-infrared region (at around 1000 nm) with energy conversion efficiency (ECE) 0.75% and short-curcuit current density 1.95 mA/cm 2.

Application of CBD-Zinc Sulfide Film as an Antireflection Coating on Very Large Area Multicrystalline Silicon Solar Cell

The low-cost chemical bath deposition (CBD) technique is used to prepare CBD-ZnS films as antireflective (AR) coating for multicrystalline silicon solar cells. The uniformity of CBD-ZnS film on large area of textured multicrystalline silicon surface is the major challenge of CBD technique. In the present work, attempts have been made for the first time to improve the rate of deposition and uniformity of deposited film by controlling film stoichiometry and refractive index and also to minimize reflection loss by proper optimization of molar percentage of different chemical constituents and deposition conditions. Reasonable values of film deposition rate (12.13 Å′/min.), good film uniformity (standard deviation <1), and refractive index (2.35) along with a low percentage of average reflection (6-7%) on a textured mc-Si surface are achieved with proper optimization of ZnS bath. 12.24% efficiency on large area (125 mm × 125 mm) multicrystalline silicon solar cells with CBD-ZnS antireflection coating has been successfully fabricated. The viability of low-cost CBD-ZnS antireflection coating on large area multicrystalline silicon solar cell in the industrial production level is emphasized.