Deposition Of Organic Thin Films Research Articles

Study of molecular layer deposition of zinc-based hybrid film as photoresist

Molecular layer deposition (MLD) of metal oxide and organic hybrid thin films has great potential to be utilized in extreme ultraviolet photoresist, thanks to its excellent uniformity on the nanometer scale thickness control. Zn has large photoelectron effect cross-section, resulting in lots of secondary electrons, which can break the organic bonds, causing changes in solubility upon the ultraviolet (UV) light exposure. In this work, Zn-based MLD thin films have been demonstrated for their potential to be used as photoresist for extreme ultraviolet(EUV) application. UV light exposure mechanisms have been proposed based on X-ray photoelectron spectroscopy(XPS) analysis.

Characterization of plasma polymerized acetonitrile film for fluorescence enhancement and its application to aptamer-based sandwich assay.

Among biosensing systems for sensitive diagnoses fluorescence enhancement techniques have attracted considerable attention. This study constructed a simple multilayered structure comprising a plane metal mirror coated with a plasma-polymerized film (PPF) as an optical interference layer on a glass slide for fluorescence enhancement. Plasma polymerization enables the easy deposition of organic thin films containing functional groups, such as amino groups. This study prepared PPFs using acetonitrile as a monomer, and the influences of washing and the output powers of plasma polymerization on PPF thickness were examined by Fourier transform infrared spectroscopy. This is because controlling the PPF thickness is vital in fluorescence enhancement. Multilayered glass slides prepared using a silver layer with 84 nm-thick acetonitrile PPFs exhibited 11- and 281-fold fluorescence enhancements compared with those obtained from the substrates with a bare surface and only modified by the silver layer, respectively. Oligonucleotides labeled with a thiol group and cyanine5 were successfully immobilized on the multilayered substrates, and the fluorescence of the acetonitrile PPFs was superior to that of the allylamine and cyclopropylamine PPFs. Furthermore, an aptamer-based sandwich assay targeting thrombin was performed on the multilayered glass slides, resulting in an approximately 5.1-fold fluorescence enhancement compared with that obtained from the substrate with a bare surface. Calibration curves revealed the relationship between fluorescence intensity and thrombin concentration of 10-1000 nM. This study demonstrates that PPFs can function as materials for fluorescence enhancement, immobilization for biomaterials, and aptamer-based sandwich assays.

Molecular layer deposition of hybrid silphenylene-based dielectric film

Molecular layer deposition (MLD) offers molecular level control in deposition of organic and hybrid thin films. This article describes a new type of inorganic–organic silicon-based MLD process where Aluminium chloride (AlCl3) and 1,4-bis(triethoxysilyl)benzene (BTEB) were used as precursors. Hybrid films were deposited at a temperature range of 300 to 500 °C and high growth per cycle (GPC) up to 1.94 Å was obtained. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were used to analyze the appearance of the film surface. The hybrid film was amorphous in low-magnification FESEM images but some particulates appeared in high-magnification FESEM images (200 k). Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Time-of-flight elastic recoil detection analysis (ToF-ERDA), and X-ray photoelectron spectroscopy (XPS) were employed to analyze the structure and composition of the hybrid film. The ratio of Al/Si in the hybrid film was 0.8. The storage environment of the films affected their capacitance, dielectric constant, leakage performance, and breakdown voltage. A film stored in a high vacuum (10–6 mbar) environment had low leakage current density (< 10–6 A × cm−2 at an applied voltage of 28 V) and a dielectric constant of 4.94, which was much smaller than after storing in a humid ambient environment.Graphical abstract

Meniscus‐Guided Deposition of Organic Semiconductor Thin Films: Materials, Mechanism, and Application in Organic Field‐Effect Transistors

Solution-processable organic semiconductors are one of the promising materials for the next generation of organic electronic products, which call for high-performance materials and mature processing technologies. Among many solution processing methods, meniscus-guided coating (MGC) techniques have the advantages of large-area, low-cost, adjustable film aggregation, and good compatibility with theroll-to-roll process, showing good research results in the preparation of high-performance organic field-effect transistors. In this review, the types of MGC techniques are first listed and the relevant mechanisms (wetting mechanism, fluid mechanism, and deposition mechanism) are introduced. The MGC processes are focused and the effect of the key coating parameters on the thin film morphology and performance with examples is illustrated. Then, the performance of transistors based on small molecule semiconductors and polymer semiconductor thin films prepared by various MGC techniques is summarized. In the third section, various recent thin film morphology control strategies combined with the MGCs are introduced. Finally, the advanced progress of large-area transistor arrays and the challenges for roll-to-roll processes are presented using MGCs. Nowadays, the application of MGCs is still in the exploration stage, its mechanism is still unclear, and the precise control of film deposition still needs experience accumulation.

Natural Dyes Used as Organic Coatings UV Protecting for Food Packages

Nowadays, the use of biodegradable and bio-derived plastics such as poly(lactic acid) (PLA) and cellulose in food packaging applications are replacing the use of different and more conventional oil-derived polymers that are much more expensive and unsuitable for the environment. However, their high transparency to ultraviolet (UV) radiation limits their current commercialization. Therefore, this study focuses on the deposition of organic thin films on commercial PLA and cellulose in order to enhance their performance, in particular for UV shielding. Coatings with different natural and biocompatible (edible) molecules, quinine and p-Coumaric acid, dispersed in different matrices are deposited by comparing different deposition techniques such as spray coating and spin coating. Morphological characterizations are carried out with atomic force microscopy (AFM) and scanning electron microscopy (SEM), with spectroscopic characterizations performed by light transmission measurements. Our results show that it is possible to enhance the UV protection of packaging using a suitable deposition with these biocompatible materials.

11‐4: Ionization Electric‐Field Organic Material Deposition Method for Reducing Shadow‐Mask Effect

To make a full‐color high‐resolution organic light emitting diodes (OLEDs) device, it is necessary to reduce mask shadow effect. The ionization‐electric field organic material deposition was proposed as an advanced method of organic material thin film deposition to reduce mask shadow effect. The organic material was ionized by contact with tungsten (W) metal mesh in vacuum chamber to which the electric field was applied to induce the organic material to be incident vertically with to the substrate. As a result, mask shadow effect was reduced by electric field without changing OLEDs device characteristics.

Innovative Organic MEH-PPV Heterojunction Device Madeby USP and PVD.

An Al/p-Si/poly[2-methoxy-5-(2-ethylhexoxy)-p-phenylenevinylene] (MEH-PPV)/Ag organic heterojunction has been prepared using homemade ultrasonic spray pyrolysis (USP) equipment for deposition of the organic thin film and physical vapor deposition (PVD) for the metallic contacts. The organic layer produced on glass was analyzed by optical and morphological methods. The bandgap of the organic thin film was found to be ~ 2.03 eV with a thickness of around 140 nm, using ultraviolet–visible (UV–Vis) and scanning electron microscopy (SEM) characterization, respectively. The amorphous nature of the MEH-PPV polymer was confirmed by its x-ray diffraction pattern. To determine the electrical parameters, the heterojunction based on MEH-PPV was characterized by current–voltage (I–V) and capacitance–voltage (C–V) measurements in the dark at room temperature. The ideality factor and barrier height of the organic heterojunction were found to be 3.6 eV and 0.56 eV to 0.59 eV, respectively, with an average series resistance of 94.39 Ω, based on the I–V characteristics. The barrier height was also calculated based on the capacitance–voltage measurements, yielding slightly different results due to the applied frequencies of 10 kHz (phi_{{text{B}}} = 0.50) and 1 MHz (phi_{{text{B}}} = 0.74) , respectively.

Nanostructure of organic semiconductor thin films: Molecular dynamics modeling with solvent evaporation

We present a procedure for simulating solution deposition of organic thin-films on explicitly modeled substrates via solvent evaporation simulations in a molecular dynamics framework. Additionally, we have developed force fields for the family of IDTBR nonfullerene acceptors, which have been widely employed in the literature as $n$-type materials in several types of organic semiconductor devices, and we analyzed their structure-property relationships using a combination of grazing incidence x-ray scattering measurements, atomistic molecular dynamics simulations, and quantum chemical calculations. We find that thermal fluctuations can have a significant impact on calculated electron transfer integrals, and that the $\ensuremath{\pi}$-stacking interactions of the electron withdrawing benzothiadiazole building blocks are key to high electron coupling in amorphous thin films of $n$-type materials.

Flexible Bottom-Gated Organic Field-Effect Transistors Utilizing Stamped Polymer Layers from the Surface of Water.

The facile sequential deposition of functional organic thin films by solution processes is critical for the development of a variety of high-performance organic devices without restriction in terms of materials and processes. Herein, we propose a simple fabrication process that entails stacking multiple layers of functional polymers to fabricate organic field-effect transistors (OFETs). The process involves stamping organic semiconducting layers formed on the surface of water onto a commonly used polymeric dielectric layer. Our scheme makes it possible to independently optimize organic semiconductor films by controlling the solvent evaporation time during the process of film formation on the surface of water. This approach eliminates the need to be concerned about any interference with adjacent layers. Utilizing this process, the fabrication of high-performance bottom-gated OFETs is demonstrated on a glass and a flexible substrate. The OFETs consist of a vertically stacked diketopyrrolopyrrole-based polymer semiconducting layer on the poly(methyl methacrylate) film with a maximum hole mobility of 0.85 cm2/V s.

Deposition of Organic Thin Films by Magnetron Sputtering

Deposition of Organic Thin Films by Magnetron Sputtering

Facile fabrication of p-type Al2O3/carbon nanocomposite films using molecular layer deposition

Molecular layer deposition (MLD) is an organic thin film deposition method with high uniformity and precise controllability over thickness. “Alucone (aluminum alkoxide)” thin film was fabricated by MLD using hydroquinone (HQ) and trimethylaluminum (TMA) precursors at 200 °C. Upon exposure to 50% humidity condition at 25 °C, HQ-TMA alucone films shows decrease of thickness and increase of roughness, but with a considerable slower rate than its diethyleneglycol-TMA analogue. The alucone MLD thin films were annealed under vacuum at temperatures between 300 and 800 °C. Upon thermal annealing, the thickness of annealed alucone film contracts, and graphitic carbon regions appear according to Raman, Auger, and XPS analyses. The post-annealed Al2O3/carbon composite shows enhanced electrical conduction compared to as-deposited alucone, becoming a p-type semiconductor. When the alucone film is annealed at 750 °C, its carrier concentration exhibits the highest value of 2.7 × 1019 cm-3, with the lowest electrical resistivity of 8.7 × 10−2 Ω cm. Currently developed p-type Al2O3/C composite films can be useful for various electronic applications.

AFM imaging and plasmonic detection of organic thin-films deposited on nanoantenna arrays

In this study, atomic force microscopy (AFM) imaging has been used to reveal the preferential deposition of organic thin-films on patterned nanoantenna array surfaces - identifying the localised formation of both monolayer and multilayer films of octadecanethiol (ODT) molecules, depending on the concentration of the solutions used. Reliable identification of this selective deposition process has been demonstrated for the first time, to our knowledge. Organic thin-films, in particular films of ODT molecules, were deposited on plasmonic resonator surfaces through a chemi-sorption process - using different solution concentrations and immersion times. The nanoantennas based on gold asymmetric-split ring resonator (A-SRR) geometries were fabricated on zinc selenide (ZnSe) substrates using electron-beam lithography and the lift-off technique. Use of the plasmonic resonant-coupling technique has enabled the detection of ODT molecules deposited from a dilute, micromolar (1 μM) solution concentration - with attomole sensitivity of deposited material per A-SRR – a value that is three orders of magnitude lower in concentration than previously reported. Additionally, on resonance, the amplitude of the molecular vibrational resonance peaks is typically an order of magnitude larger than that for the non-resonant coupling. Fourier-transform infrared (FTIR) spectroscopy shows molecule specific spectral responses – with magnitudes corresponding to the different film thicknesses deposited on the resonator surfaces. The experimental results are supported by numerical simulation.

P‐70: Single Array Nozzle Source Method for Homogeneous Mixed Organic Thin Film and Low Mask Shadow in 6GH AMOLED Mass Production

We have developed Single Array Nozzle source (SAN source) organic thin film deposition method for 6G half size AMOLED mass production. The special feature of SAN source set is all of nozzles are arranged in one single line even if when we make 3 material mixed thin film. And the distance within each edge nozzle of SAN source is shorter than substrate size. We expect than SAN source set can improve homogeneity of mixed thin film and resolution of AMOLED pixel.

Effect of the nozzle tip’s geometrical shape on electrospray deposition of organic thin films

Electrospray deposition (ESD) is a favorable wet fabrication technique for organic thin films. We investigated the effects of the nozzle tip’s geometrical shape on the spraying properties of an organic solution used for ESD. Five types of cylindrical metal nozzles with zero (flat end) to four protrusions at the tips were prepared for depositing a solution of a small-molecule compound, tris(8-hydroxyquinolinato)aluminum (Alq3) solution. We confirmed that the diameter of the deposited droplets and their size dispersion decreased with an increase in the number of protrusions. The area occupation ratio of small droplets with a diameter smaller than 2 µm increased from 21 to 83% as the number of protrusions was increased from zero to four. The surface roughness root mean square of 60-nm-thick Alq3 films substantially improved from 32.5 to 6.8 nm with increasing number of protrusions.

Enhancement of Fluorescence-Based Sandwich Immunoassay Using Multilayered Microplates Modified with Plasma-Polymerized Films.

A functional modification of the surface of a 96-well microplate coupled with a thin layer deposition technique is demonstrated for enhanced fluorescence-based sandwich immunoassays. The plasma polymerization technique enabling the deposition of organic thin films was employed for the modification of the well surface of a microplate. A silver layer and a plasma-polymerized film were consecutively deposited on the microplate as a metal mirror and the optical interference layer, respectively. When Cy3-labeled antibody was applied to the wells of the resulting multilayered microplate without any immobilization step, greatly enhanced fluorescence was observed compared with that obtained with the unmodified one. The same effect could be also exhibited for an immunoassay targeting antigen directly adsorbed on the multilayered microplate. Furthermore, a sandwich immunoassay for the detection of interleukin 2 (IL-2) was performed with the multilayered microplates, resulting in specific and 88-fold–enhanced fluorescence detection.

Nucleation and strain-stabilization during organic semiconductor thin film deposition.

The nucleation mechanisms during solution deposition of organic semiconductor thin films determine the grain morphology and may influence the crystalline packing in some cases. Here, in-situ optical spectromicroscopy in reflection mode is used to study the growth mechanisms and thermal stability of 6,13-bis(trisopropylsilylethynyl)-pentacene thin films. The results show that the films form in a supersaturated state before transforming to a solid film. Molecular aggregates corresponding to subcritical nuclei in the crystallization process are inferred from optical spectroscopy measurements of the supersaturated region. Strain-free solid films exhibit a temperature-dependent blue shift of optical absorption peaks due to a continuous thermally driven change of the crystalline packing. As crystalline films are cooled to ambient temperature they become strained although cracking of thicker films is observed, which allows the strain to partially relax. Below a critical thickness, cracking is not observed and grazing incidence X-ray diffraction measurements confirm that the thinnest films are constrained to the lattice constants corresponding to the temperature at which they were deposited. Optical spectroscopy results show that the transition temperature between Form I (room temperature phase) and Form II (high temperature phase) depends on the film thickness, and that Form I can also be strain-stabilized up to 135 °C.

Deposition characteristics of small-molecule CBP:PBD:TPD:Ir(mppy)3 organic thin films using a modified electrospray deposition method

The development of a solution-based technique for the deposition of small-molecule organic thin films is desirable for the advancement of organic devices. In this study, we investigated the deposition characteristics of an organic thin film deposited by modified electrospray deposition with three typical spraying modes: Taylor cone, convergent jet, and multijet. The results indicate that the multijet mode can generate the smallest droplets with the narrowest size distribution. Using the multijet mode, we deposited a pinhole-free, smooth CBP:PBD:TPD:Ir(mppy)3 small-molecule organic film with a root-mean-square surface roughness of 2.5 nm.

Transient phases during fast crystallization of organic thin films from solution

We report an in situ microbeam grazing incidence X-ray scattering study of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) organic semiconductor thin film deposition by hollow pen writing. Multiple transient phases are observed during the crystallization for substrate temperatures up to ≈93 °C. The layered smectic liquid-crystalline phase of C8-BTBT initially forms and preceedes inter-layer ordering, followed by a transient crystalline phase for temperature &amp;gt;60 °C, and ultimately the stable phase. Based on these results, we demonstrate a method to produce extremely large grain size and high carrier mobility during high-speed processing. For high writing speed (25 mm/s), mobility up to 3.0 cm2/V-s has been observed.

Artificial biomembrane based on DPPC — Investigation into phase transition and thermal behavior through ellipsometric techniques

Organic thin film deposition presents a multiplicity of challenges. Most notably, layer thickness control, homogeneity and subsequent characterization have been not cleared yet. Phospholipid bilayers are frequently used to model cell membranes. Bilayers can be disrupted by changes in mechanical stress, pH and temperature. The strategy presented in this article is based on thermal study of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) through analysis of slight changes in material thickness.The sample was prepared by depositing X- or Y-type DPPC bilayers using Langmuir–Blodgett technique over silicon wafer. Thus, molecular inclination degree, mobility and stability of phases and their respective phase transitions were observed and analyzed through ellipsometric techniques during heating cycles and corroborated by Grazing Incidence X-ray Diffraction and Atomic Force Microcopy measurements. DPPC functional group vibrations were detected by Raman spectra analysis. Scanning Electron Microscope with Field Emission gun (FE-SEM) and conventional SEM micrographs were also used to characterize sample morphology, demonstrating that homogenous bilayer formations coexist with some vesicles or micelles at surface level. Contact angle measurements corroborate DPPC surface wettability, which is mainly related to surface treatment methods of silicon wafer used to create either hydrophilic or hydrophobic nature regarding the substrate surface. Also, shifting and intensity changes of certain functional groups into Raman spectra confirm water presence between DPPC layers. Signal analysis detects certain interdigitation between aliphatic chains. These studies correspond to the base of future biosensors based on proteins or antimicrobial peptides stabilized into phospholipid bilayers over thin hydrogel films as moist scaffold.

Integrated OLED as excitation light source in fluorescent lateral flow immunoassays.

The integration of organic light emitting diodes (OLEDs) as excitation light sources for quantum dot-based fluorescent lateral flow immunoassay systems (LFIA) was investigated. This approach has the potential to deliver a sensitive visible detection scheme for low-cost, disposable lab-on-chip point-of-care (POC) diagnosis system. Thin film phosphorescent green OLEDs fabricated on plastic substrates were integrated on-chip to excite the test line of a quantum dot-based LFIA (QD-LFIA). OLEDs were fabricated by sequential deposition of organic thin films (total of ~100 nm) onto ITO-coated PET substrates. CdSe/ZnS QDs emitting at 655 nm and Au nanoparticles (NP - 10 nm size) conjugated antibodies were used for the fluorescence QD-LFIA and conventional reflection-mode Au NP-LFIA, respectively. Thin plastic color light filters were integrated for filtering the excitation light source and, thereby, increasing the contrast of the emitted light for optimized visual detection. Integration of the OLED and color filters with the analytical membrane was achieved using adhesive techniques facilitated by the planar nature of the layers, which suggests possible large scale manufacturing using roll-to-roll processing. Gray scale analysis from digital images captured with a digital camera was used to quantify the visual sensitivity. The signal intensity, signal-to-noise ratio (SNR) and the limit of detection (LOD) of OLED integrated QD-LFIAs were compared to Au NP LFIAs. OLED QD-LFIA exhibited superior performance in all signal aspects: 7-8× higher signal intensity and SNR, and a 7× lower LOD of 3 nM (measured at S/N=3). These results demonstrate the potential of OLED-integrated in LFIA devices for obtaining sensitive, fast and low-cost POC diagnostics.