Fabrication Of Organic Thin Films Research Articles

Spin-casting of Micron-Scale Thick PMMA Films with Embedded Au Nanoparticles Formed by Laser Ablation in Liquid

Background: A Facile, scalable approach to fabrication of organic thin films with an embedded layer of nanoparticles in the ambient environment. The approach is based on step-bystep spin-coating of polymethylmethacrylate (PMMA) films and a nanoparticle layer. Objective: The goal of the present work is to fabricate a sandwich structure of the PMMA films for the top and bottom layers of a sandwich structure as well as a middle layer of nanoparticles formed in solution by the Laser Ablation in Liquid (LAL) method. Methods: First, a PMMA thin film was fabricated by spin-casting of PMMA solution in ethylacetate. Secondly, a solution of Au nanoparticles synthesized by laser ablation in ethanol was spin-cast on a prefabricated PMMA film. The distribution of Au nanoparticles and the morphology of the resulting film were analyzed using scanning electron microscopy (SEM), optical microscopy, and atomic microscopy (AFM). Finally, another PMMA layer was spin-cast on the nanoparticle-decorated film. Results: A hybrid organic film with the embedded layer of nanoparticles was fabricated using the spin-casting method for top and bottom layers as well as for the middle layer of Au nanoparticles fabricated by laser ablation in ethanol by a pulsed UV laser. Statistical and fractal analysis shows uniform distribution of nanoparticles on length scale above ten microns. Conclusion: Spin-cast-based layer-by-layer approach to fabrication of sandwich structures of organic films with embedded nanoparticlesis a facile and scalable method for hybrid organic - nanoparticle films. This approach can be extended for the fabrication of multi-layered hybrid structures.

Overview of electric-field-induced deposition technology in fabricating organic thin films

The progress in the fabrication of organic thin films by electric-field induced deposition (EFID) technology is summarized. The applicable materials, deposition mechanisms, processing parameters, derivative technologies, wide applications, and possible challenges are discussed.

3B11 分子配向性有機絶縁膜上への有機半導体薄膜の作製とその有機TFT特性への影響(分子配向エレクトロニクス,口頭発表,2015年日本液晶学会討論会)

3B11 分子配向性有機絶縁膜上への有機半導体薄膜の作製とその有機TFT特性への影響(分子配向エレクトロニクス,口頭発表,2015年日本液晶学会討論会)

Complex Behavior of Caffeine Crystallites on Muscovite Mica Surfaces.

Defined fabrication of organic thin films is highly desired in technological, as well as pharmaceutical, applications since morphology and crystal structure are directly linked to physical, electrical, and optical properties. Within this work, the directed growth of caffeine deposited by hot wall epitaxy (HWE) on muscovite mica is studied. Optical and atomic force microscopy measurements reveal the presence of caffeine needles exhibiting a preferable alignment in the azimuthal directions with respect to the orientation of the defined mica surface. Specular X-ray diffraction and X-ray diffraction pole figure measurements give evidence that the β-polymorphic form of caffeine forms on the mica surface. All results consent that caffeine molecules have an edge-on conformation i.e. minimizing their interaction area with the surface. Furthermore, the azimuthal alignment of the long caffeine needle axis takes place along the [11̅0], [100], and [110] real space directions of mica; needles are observed every 60° azimuthally. While mica has a complex surface structure with mirror planes and lowered oxygen rows, the slightly disturbed 3-fold symmetry dictates the crystal alignment. This is different to previous findings for solution cast caffeine growth on mica. For HWE the needles align solely along the mica main directions whereby solution cast needles show an additional needle splitting due to a different alignment of caffeine with respect to the surface.

Combinatorial MAPLE gradient thin film assemblies signalling to human osteoblasts

There is increased interest in smart bioactive materials to control tissue regeneration for the engineering of cell instructive scaffolds. We introduced combinatorial matrix-assisted pulsed laser evaporation (C-MAPLE) as a new method for the fabrication of organic thin films with a compositional gradient. Synchronized C-MAPLE of levan and oxidized levan was employed to assemble a two-compound biopolymer film structure. The gradient of the film composition was validated by fluorescence microscopy. In this study, we investigated the cell response induced by the compositional gradient using imaging of early osteoblast attachment and analysis of signalling phosphoprotein expression. Cells attached along the gradient in direct proportion to oxidized levan concentration. During this process distinct areas of the binary gradient have been shown to modulate the osteoblasts’ extracellular signal-regulated kinase signalling with different propensity. The proposed fabrication method results in the preparation of a new bioactive material, which could control the cell signalling response. This approach can be extended to screen new bioactive interfaces for tissue regeneration.

One-step fabrication of self-assembled peptide thin films with highly dispersed noble metal nanoparticles.

Fabrication of organic thin films with highly dispersed inorganic nanoparticles is a very challenging topic. In this work, a new approach that combines electron-induced molecular self-assembly with simultaneous nanoparticle formation by room temperature electron reduction was developed to prepare peptide thin films with highly dispersed noble metal nanoparticles. Argon glow discharge was employed as the resource of electrons. The peptide motif KLVFF (Aβ16-20) self-assembled into two-dimensional membranes under the influence of hydrated electrons, while the metal ions in solution can be simultaneously reduced by electrons to form nanoparticles. Our TEM imaging reveals that metal nanoparticles were well-distributed in the resulting peptide thin films. Our results also suggest that the size of metal nanoparticles can be tuned by varying the initial concentration of the metal ion. This simple approach can be viewed as a promising strategy to create hybrid thin films that integrate functional inorganics into biomolecule scaffolds.

Micropatterning of functional dye films on wettability-patterned surfaces using soft liquid-phase adsorption

We discuss a “soft” liquid-phase adsorption (SLPA) technique to control formation of organic dye films on wettability-patterned templates by using methanol/hexane emulsions. Wettability-patterned templates were fabricated by the formation of self-assembled monolayers of silane-coupling agents on glass plates followed by UV-ozone treatment through a metal mask. Rhodamine B and thymol blue films were formed selectively on the hydrophilic regions of the wettability-patterned templates. The thickness of the rhodamine B films increased with a decrease in immersion temperature and with an increase in immersion angle of the wettability-patterned templates in the emulsions. The thickness of the thymol blue films was significantly larger than that of the films fabricated by conventional film-forming techniques such as spin-coating and dip-coating. The thymol blue films served as pH-responsive devices under exposure to HCl and NH3 gasses. The SLPA technique allows for the fabrication of organic thin films on wettability-patterned templates with little material consumption and a few film-forming processes, contributing to application to the fabrication of organic photonics and electronics devices with reduction of environmental burdens.

Modeling morphology evolution during solvent-based fabrication of organic solar cells

Solvent-based thin-film deposition constitutes a popular class of fabrication strategies for manufacturing organic electronic devices like organic solar cells. All such solvent-based techniques usually involve preparing dilute blends of electron-donor and electron-acceptor materials dissolved in a volatile solvent. After some form of coating onto a substrate to form a thin film, the solvent evaporates. An initially homogeneous mixture separates into electron-acceptor rich and electron-donor rich regions as the solvent evaporates. Depending on the specifics of the blend, processing conditions, and substrate characteristics different morphologies are typically formed. Experimental evidence consistently confirms that the resultant morphology critically affects device performance. A computational framework that can predict morphology evolution can significantly augment experimental analysis. Such a framework will also allow high throughput analysis of the large phase space of processing parameters, thus yielding considerable insight into the process–structure–property relationships governing organic solar cell behavior.In this paper, we formulate a computational framework to predict evolution of morphology during solvent-based fabrication of organic thin films. This is accomplished by developing a phase field-based model of evaporation-induced and substrate-induced phase-separation in ternary systems. This formulation allows most of the important physical phenomena affecting morphology evolution during fabrication to be naturally incorporated. We discuss the various numerical and computational challenges associated with a three dimensional, finite-element based, massively parallel implementation of this framework. This formulation allows, for the first time, to model three-dimensional nanomorphology evolution over large time spans on device scale domains. We illustrate this framework by investigating and quantifying the effect of various process and system variables on morphology evolution. We explore ways to control the morphology evolution by investigating different evaporation rates, blend ratios and interaction parameters between components.

Molecular Layer Deposition of Thiol−Ene Multilayers on Semiconductor Surfaces

The fabrication of organic thin films with controlled chemical structure in the vertical direction (parallel to surface normal) is important for many practical and technological applications in organic electronics, chemical-resistant films, and biocompatible materials, among others. In order to achieve composition control in the z-direction, molecular layer deposition (MLD: covalent layer-by-layer assembly) of thin, organic films on silicon, silicon oxide, and germanium surfaces was carried out, using the well-established UV-induced thiol-ene reaction. Through successive contact of an interface with dithiol and diene molecules under UV irradiation for short periods (approximately 30 min, room temperature), well-defined thin films can be obtained. Linear increases in film thickness with respect to layer number were obtained for shorter aliphatic dienes and dithiols (C < or = 8), but with longer molecules and with aromatic substrates a self-limiting situation sets in whereby both ends of the molecule react with the surface, arresting film growth. The functionalized interfaces were characterized by ellipsometry, X-ray photoelectronic spectroscopy, and atomic force microscopy.

Combinatorial approach to the fabrication of organic thin films

We demonstrate combinatorial approach in investigation of organic thin film fabrication. “Combinatorial substrate screening”, which is the deposition onto several kinds of substrates simultaneously, is useful to choose suitable substrate for organic thin film growth. “Combinatorial thickness-gradient films” can be fabricated using a moving mask which travels from an edge to another edge of substrate continuously during the deposition. The combinatorial thickness-gradient film can be regarded as the library for time evolution of film growth during the deposition. This mapping can serve as a powerful method for the research of growth of thin film in an initial stage. Besides, combinatorial thickness-gradient film can be utilized for the examination of a buffer layer effect. These techniques enable us to quickly optimize for the fabrication of high-quality organic thin films.

Fabrication of Organic Thin Films by Dual Molecular Beam Deposition with Excimer Laser.

Fabrication of Organic Thin Films by Dual Molecular Beam Deposition with Excimer Laser.

Applicability of Laser Ablation Deposition to Organic Thin Film Fabrication

Applicability of Laser Ablation Deposition to Organic Thin Film Fabrication

Applicability of Laser Ablation Deposition to Organic Thin Film Fabrication.

Applicability of Laser Ablation Deposition to Organic Thin Film Fabrication.

Organic thin films formation by laser ablation.

We have developed a new organic thin film fabrication process, which makes use of laser ablation followed by photochemical reaction using excimer laser. In this study, we investigated the conditions for good organic films formation such as laser fluence, substrate temperature, using stoichiometrically equivalent mixture of terephthaloylchloride and p-phenylenediamine as ablation source. It was shown that thin organic polymer films were formed under the conditions where laser fluence 20-310mJ/cm 2 and substrate temperature 200-300°C through FT-IR characterization.

Organic Thin Film Fabrication by Ultrahigh Vacuum Technique

Organic Thin Film Fabrication by Ultrahigh Vacuum Technique