Plasma Polymerized Thin Films Research Articles

A study of the initial film growth of PEG-like plasma polymer films via XPS and NEXAFS

The chemistry of substrate–film interface (underside) of di(ethylene glycol) dimethyl ether plasma polymer (DGpp) films has been studied directly and compared to the top layer of the film (topside). By depositing the plasma polymer films onto indium tin oxide (ITO) glass, the films were easily delaminated from the substrate. The top- and underside of the films were examined by X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. It was found that a rapid increase in pressure during plasma polymerization results in steep chemical gradients in the films, while small pressure changes do not lead to chemical gradient formation. These observations validate the findings of previous neutron reflectometry modeling studies of this class of plasma polymer thin film. In addition, subtle variations in plasma polymer film chemistry were observed between different substrates they were deposited onto. This approach will allow additional studies on the mechanisms of early plasma polymer thin film formation with various monomers.

Effect of plasma surface functionalization on preosteoblast cells spreading and adhesion on a biomimetic hydroxyapatite layer formed on a titanium surface

This study examined the plasma surface modification of biomimetic hydroxyapatite (HAp) formed on a titanium (Ti) surface as well as its influence on the behavior of preosteoblast cells. Ti substrates pre-treated with a plasma-polymerized thin film rich in carboxyl groups were subjected to a biomimetic process in a simulated body fluid solution to synthesize the HAp. The HAp layer grown on Ti substrate was then coated with two types of plasma polymerized acrylic acid and allyl amine thin film. The different types of Ti substrates were characterized by attenuated total reflection Fourier transform infrared spectroscopy, energy dispersive spectroscopy and X-ray diffraction. HAp with a Ca/P ratio from 1.25 to 1.38 was obtained on the Ti substrate and hydrophilic carboxyl (COOH) and amine (NH2) functional groups were introduced to its surface. Scanning electron microscopy was used to observe the surface of the HAp coatings and the morphology of MC3T3-E1 cells. These results showed that the COOH-modified HAp surfaces promoted the cell spreading synergistically by changing the surface morphology and chemical state.NH2 modified HAp had the lowest cell spreading and proliferation compared to HAp and COOH-modified HAp. These results correspond to fluorescein analysis, which showed many more cell spreading of COOH/HAp/Ti surface compared to HAp and NH2 modified HAp. A MTT assay was used to evaluate cell proliferation. The results showed that the proliferation of MC3T3-E1 cells increased in the order of COOH/HAp/Ti>HAp/Ti>NH2/Ti>Ti, corresponding to the effect of cell spreading for 6 days. The change in morphology and the chemical surface properties of the biomaterial via plasma polymerization can affect the behavior of MC3T3-E1 cells.

The optical properties of plasma polymerized polyaniline thin films

We report herein the characterizations of polyaniline thin films synthesized using double discharge plasma system. Quartz glass substrates were coated at a pressure of 80Pa, 19.0kV pulsed and 1.5kVdc potential. The substrates were located at different regions in the reactor to evaluate the influence of the position on the morphological and molecular structure of the obtained thin films. The molecular structure of the thin films was investigated by Fourier transform infrared (FTIR) and UV–visible photospectrometers (UV–vis), and the morphological studies were carried out by scanning electron microscope. The FTIR and UV–vis data revealed that the molecular structures of the synthesized thin films were in the form of leuocoemeraldine and exhibited similar structures with the films produced via chemical or electrochemical methods. The optical energy band gap values of the as-grown samples ranged from 2.5 to 3.1eV, which indicated that these materials have potential applications in semiconductor devices. The refractive index in the transparent region (from 650 to 1000nm) steadily decreased from 1.9 to 1.4 and the extinction coefficient was found to be on order of 10−4. The synthesized thin films showed various degrees of granular morphologies depending on the location of the substrate in the reactor.

Thickness Dependent Direct Current Electrical Conduction in Plasma Polymerized Pyrrole Monolayer Thin Films

The thickness dependent direct current electrical conduction mechanism in plasma polymerized pyrrole (PPPy) monolayer thin films has been discussed in this paper. A parallel plate capacitively coupled glow discharge reactor was used to deposit PPPy thin films at room temperature onto glass substrates. The Fourier Transform Infrared (FTIR) analyses showed that the spectrum of PPPy is very much different than that of the pyrrole monomer and indicated that the monomer has undergone the re-organization during the plasma polymerization. The current density-voltage (J-V) characteristics of PPPy monolayer thin films of different thicknesses indicated an increase in electrical conductivity in the thin films of lower thickness. It is seen that in the low voltage region, the current conduction obeys Ohms law while the charge transport phenomenon appears to be the space charge limited conduction (SCLC) in the higher voltage region. The permittivity, free charge carrier density, and the mobility of the charges of the PPPy monolayer thin films have been calculated from the experimental data of J-V characteristics and found to be 1.07 × 10-10 C2N-1m-2, (3.56 ± 0.01) × 1022 m-3, (4.4 ± 0.01) × 10-19 m2 V-1s-1 respectively.

Contradictory ageing behaviour and optical property of iodine doped and H2SO4 doped pulsed DC plasma polymerized aniline thin films

Polymerization of aniline in the presence of H2SO4 and iodine vapour is carried out using pulsed DC glow discharge plasma. The as prepared iodine doped plasma polymerized aniline films are found to be highly crystalline due to some crystal structure formed by the iodine incorporated into the film and the ex-situ H2SO4 doped films are found to be amorphous. However, the structure of the iodine doped films transforms to amorphous one while that of the ex-situ H2SO4 doped films transforms to crystalline one due to the effect of ageing. The optical band gap of the samples decreases depending upon the level of doping and annealing, having minimum optical band gap for iodine doped plasma polymerized aniline. Due to ageing, the optical property of the H2SO4 doped film is found to become superior while for iodine doped films a negligible change of the optical property has been noticed even after six months of ageing.

플라즈마 중합된 Styrene 박막을 터널링층으로 활용한 부동게이트형 유기메모리 소자

The thin insulator films for organic memory device were made by the plasma polymerization method using the styrene monomer which was not the wet process but the dry process. For the formation of stable plasma, we make an effort for controlling the monomer with bubbler and circulator system. The thickness of plasma polymerized styrene insulator layer was 430 nm, the thickness of the Au memory layer was 7 nm thickness of plasma polymerized styrene tunneling layer was 30, 60 nm, the thickness of pentacene active layer was 40 nm, the thickness of source and drain electrodes were 50 nm. The I-V characteristics of fabricated memory device got the hysteresis voltage of 45 V at 40/-40 V double sweep measuring conditions. If it compared with the results of previous paper which was the organic memory with the plasma polymerized MMA insulation thin film, this result was greater than 18 V, the improving ratio is 60%. From the paper, styrene indicated a good charge trapping characteristics better than MMA. In the future, we expect to make the organic memory device with plasma polymerized styrene as the memory thin film.

Aging effects of plasma polymerized ethylenediamine (PPEDA) thin films on cell-adhesive implant coatings

Thin plasma polymer films from ethylenediamine were deposited on planar substrates placed on the powered electrode of a low pressure capacitively coupled 13.56MHz discharge. The chemical composition of the plasma polymer films was analyzed by Fourier Transform Infrared Reflection Absorption Spectroscopy (FT-IRRAS) as well as by X-ray photoelectron spectroscopy (XPS) after derivatization of the primary amino groups. The PPEDA films undergo an alteration during the storage in ambient air, particularly, due to reactions with oxygen. The molecular changes in PPEDA films were studied over a long-time period of 360days. Simultaneously, the adhesion of human osteoblast-like cells MG-63 (ATCC) was investigated on PPEDA coated corundum blasted titanium alloy (Ti-6Al-4V), which is applied as implant material in orthopedic surgery. The cell adhesion was determined by flow cytometry and the cell shape was analyzed by scanning electron microscopy. Compared to uncoated reference samples a significantly enhanced cell adhesion and proliferation were measured for PPEDA coated samples, which have been maintained after long-time storage in ambient air and additional sterilization by γ−irradiation.

Electroluminescence and Photoluminescence of Conjugated Polymer Films Prepared by Plasma Enhanced Chemical Vapor Deposition of Naphthalene

Polymer light-emitting devices were fabricated utilizing plasma polymerized thin films as emissive layers. These conjugated polymer films were prepared by RF plasma enhanced chemical vapor deposition using naphthalene as monomer. The effect of different applied powers on the chemical structure and optical properties of the conjugated polymers was investigated. Fourier transform infrared (FTIR) and Raman spectroscopies confirmed that a conjugated polymer film with a 3-D cross-linked network was developed. By increasing the power, products tended to form as highly cross-linked polymer films. The fabricated devices showed broadband Electroluminescence (EL) emission peaks with center at 535–550 nm. Photoluminescence (PL) spectra of plasma polymers showed different excimeric emissions, resulted from crosslinked architecture. As the plasma power increased, the optical properties showed two different domains; up to 200 W, EL, PL and UV–Vis spectra red-shifted and broadened significantly. At higher powers, a reverse behavior was observed. Also, the relation between the film structure and plasma species was investigated using optical emission spectroscopy.

Structural and optical properties of plasma polymerized o-methoxyaniline thin films

Plasma polymerized o-methoxyaniline (PPOMA) thin films of different thicknesses were prepared in glow discharge plasma using a parallel plate capacitively coupled polymerization reactor. The PPOMA thin films are smooth, flawless and pinhole free. Fourier transform infrared spectra reveal a decrease of absorption intensity and disappearance of some absorption peaks for PPOMA as compared to those of OMA, indicating the formation of the thin film with modified/changed chemical structure. Analyses of the ultraviolet–visible spectroscopic results reveal that the allowed indirect (Egi) and direct (Egd) band gap energies have values in the range 1.68 to 2.08eV and 2.90 to 3.08eV, respectively for PPOMA thin films of thicknesses from 100 to 300nm. The Egi of the experimental PPOMA thin films does not show any definite trend with film thickness, whereas the Egd shows weak dependence on film thickness.

Composite Thin Film Obtained Using Tetraethoxysilane and Aimed at VOCs Detection

The aim of this work was production of tetraethoxysilane (TEOS) plasma polymerized thin films and optimization of their physical-chemical characteristic for sensor development. The films were analyzed using several techniques. It was possible to produce composites (graphite clusters imbibed by silicon oxide film) made from only one reactant (TEOS). Deposition rate can vary significantly, reaching a maximum of 30 nm/min; cluster formation and their size widely depending on deposition parameters. The film surface was hydrophobic but can be wetted by organic compounds, probably due to carbon radicals. These films are good candidates for sensor development.

Nano-ordered thin films achieved by soft atmospheric plasma polymerization

Plasma polymer thin films are of great interest in surface engineering in a wide range of applications. Herein, by using soft atmospheric plasma deposition parameters and by adapting these conditions to the used perfluorodecyl and dodecyl acrylates precursors, it is possible to get a high retention of monomer functionalities and a polymerization close to conventional methods. Molecular investigation revealed the presence of polymeric moieties and the mechanism of plasma polymerization has been mainly based on the polymerization by activation of the ethylenic groups. X-ray diffraction analyses have shown the presence of a smectic lamellar where the polyacrylate backbone was the amorphous phase and fluorinated and alkyl side chains were the hexagonal crystalline section. Wetting properties have been evaluated and finally showed hydrophobic surfaces

Surface Modification of Plasma Polymer Thin Films for DNA Fixation by Atmospheric Pressure Plasma Treatment

The atmospheric pressure plasma treatment on plasma polymer thin films was investigated to control the immobilization of DNA alignment. The amine groups of aminopropyltriethoxysilane have been generally used for the fixation of DNA on the substrate. However, it is easily influenced by humidity, and so it is hard to control precisely the formation of the self-assembled monolayer. The plasma polymer thin films with the atmospheric pressure plasma treatment are expected to be hardly influenced by humidity. Moreover, the densities of the amine groups are expected to be controlled by the treatment. In this work, organic and organic-inorganic hybrid plasma polymer thin films were formed on Si(100) by plasma enhanced chemical vapor deposition using methylcyclohexane and tetraethylorthosilane (TEOS), and the amine groups were formed on the surfaces by N2 atmospheric pressure plasma treatment. Fourier-transform infrared absorption spectroscopy showed that the amine groups were increased with the treatment. The surface densities of the amine groups were obtained from averaged extinction coefficients of UV–visible absorption spectra. DNA fixation was successfully performed with a tilting method for aligning well stretched DNAs on the surfaces, through optimization of the surface condition in the treatment.

Surface Modification of Plasma Polymer Thin Films for DNA Fixation by Atmospheric Pressure Plasma Treatment

The atmospheric pressure plasma treatment on plasma polymer thin films was investigated to control the immobilization of DNA alignment. The amine groups of aminopropyltriethoxysilane have been generally used for the fixation of DNA on the substrate. However, it is easily influenced by humidity, and so it is hard to control precisely the formation of the self-assembled monolayer. The plasma polymer thin films with the atmospheric pressure plasma treatment are expected to be hardly influenced by humidity. Moreover, the densities of the amine groups are expected to be controlled by the treatment. In this work, organic and organic-inorganic hybrid plasma polymer thin films were formed on Si(100) by plasma enhanced chemical vapor deposition using methylcyclohexane and tetraethylorthosilane (TEOS), and the amine groups were formed on the surfaces by N2 atmospheric pressure plasma treatment. Fourier-transform infrared absorption spectroscopy showed that the amine groups were increased with the treatment. The surface densities of the amine groups were obtained from averaged extinction coefficients of UV–visible absorption spectra. DNA fixation was successfully performed with a tilting method for aligning well stretched DNAs on the surfaces, through optimization of the surface condition in the treatment.

Study on the Characteristics of ThioPP Thin Films for Low-κ Applications

The thiophene plasma polymer was deposited on silicon(100) substrates by PECVD (Plasma Enhanced Chemical Vapor Deposition) with homemade stainless steel vacuum chamber. Thiophene was utilized as organic precursor with hydrogen gas as bubbling gas. Argon gas was used as a carrier gas. To analyze the electrical properties of the plasma polymerized thin films, the plasma-polymer thin films were grown under various RF power condition. The as-grown plasma-polymer thin films were analyzed by atomic force microscopy (AFM), scanning electron microscopy (SEM), measuring the capacitance, impedance analyzer, ellipsometry, Fourier Transform Infrared spectroscopy (FT-IR), and water contact angle measurement. AFM and SEM images showed smooth surfaces of thin films with increasing RF power. An impedance analyzer was utilized for the measurements of I-V curves (for leakage current density) and capacitance (for dielectric constant). Refractive indices were increased by increasing RF power. The IR spectra showed that the plasma polymer thin films have totally different chemical functionalities from liquid thiophene precursor, as well as the changing chemical functionalities of the thin films caused by various RF powers. The best dielectric constant is 2.52 in this study.

Pulsed DC discharge for synthesis of conjugated plasma polymerized aniline thin film

The polymerization of aniline in pulsed dc plasma is studied and the effects of variation of pressure, power, frequency and duty cycle on the chemical structure of the obtained film are examined. During the film deposition optical emission spectroscopy is used to investigate the molecular dissociation of aniline. The chemical structure of the films is characterized using Fourier transform infra-red spectroscopy. The surface morphology is studied using atomic force microscopy. Results show the retention of polyaniline like structure having conjugated nature at some particular discharge conditions. Moreover, it is observed that a strong dependence of film chemistry is obvious on the discharge power, reactor pressure, pulse repetition frequency and duty cycle. The advantages of the pulsed dc for deposition of conjugated plasma polymerizes thin film have been highlighted.

A ToF-SIMS and XPS study of protein adsorption and cell attachment across PEG-like plasma polymer films with lateral compositional gradients

In this work we report a detailed X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) study of poly(ethylene glycol) PEG-like chemical gradients deposited via plasma enhanced chemical vapour deposition (PECVD) at two different load powers using diethylene glycol dimethyl ether (DG) as a monomer. Principal component analysis (PCA) was applied to the ToF-SIMS data both before and after protein adsorption on the plasma polymer thin films. Results of the PCA loadings indicated a higher content of hydrocarbon fragments across the higher load power gradient, which adsorbed higher amounts of proteins. Gradients deposited at a lower load power retained a higher degree of monomer like functionality as did the central region directly underneath the knife edge electrode. Analysis of the adsorption of serum proteins (human serum albumin and fetal bovine serum) was monitored across the gradient films and increased with decreasing ether (PEG-like) film chemistries. The effect of protein incubation time on the levels adsorbed fetal bovine serum on the plasma polymer films was critical, with significantly more protein adsorbing after 24hour incubation times on both gradient films. The attachment of HeLa cells on the gradients appeared to be dictated not only by the surface chemistry, but also by the adsorption of serum proteins. XPS analysis revealed that at surface ether concentrations of less than 70% in the gradient films, significant increases in protein and cell attachment were observed.

Sensing based on Mach-Zehnder interferometer and hydrophobic thin films used on volatile organic compounds detection

This paper presents the project, optimization, design details, and fabrication of an optical chemical sensor based on a Mach-Zehnder interferometer (MZI), fabricated with metal-oxide semiconductor compatible processes and materials. The sensing material is hexamethyldissilazane (HMDS) plasma polymerized thin film, which exhibits hydrophobic characteristics, high resistance to acid or basic solution, and adsorption of polar and nonpolar organic compounds. Both reference and sensor arms of the fabricated MZIs are covered with HMDS thin film in order to keep the device balanced. Different substances, such as water, 2-propanol, and hexane vapors are investigated. The high sensitivity of the MZI structure, associated with refractive index variations of about 10−4, paves the way for a myriad of sensor applications, such as humidity, organic compounds, proteins, antibodies (antigens), enzymes, pesticides, and others. The minimum detectable measurements were 4.6 mg/min for n-hexane and 0.2 mg/min for 2-propanol.

Conducting Plasma Polymerized Polypyrrole Thin Films as Carbon Dioxide Gas Sensors

AbstractThis paper describes the production of conducting polypyrrole (PPy) thin films by plasma‐enhanced chemical vapor deposition (PECVD) and its posterior use for sensing applications of carbon dioxide (CO2). Since PECVD yields the non‐conducting form of PPy, a doping process consisting of exposure to iodine vapor is required to obtain electrically conducting samples. Differences in the chemical state and topography between the doped and undoped systems are studied and characterized to demonstrate the doping effect on the polymer. Furthermore, changes in conductivity after exposure to CO2 gas are measured to evaluate the use of these thin films as chemical sensors. The results suggest that plasma polymerized films show a good sensitivity and reproducibility in the analyte detection. magnified image

Process Condition Considered Preparation and Characterization of Plasma Polymerized Methyl Methacrylate Thin Films for Organic Thin Film Transistor Application

Process Condition Considered Preparation and Characterization of Plasma Polymerized Methyl Methacrylate Thin Films for Organic Thin Film Transistor Application

Process Condition Considered Preparation and Characterization of Plasma Polymerized Methyl Methacrylate Thin Films for Organic Thin Film Transistor Application

Plasma polymerized methyl methaclylate (ppMMA) thin films were prepared with various process conditions such as inductively coupled plasma (ICP) power, substrate bias power, working pressure, substrate heating temperature, substrate position, and monomer flow rate. Thickness, surface morphology, dielectric constant, and leakage current of the ppMMA thin films were investigated for application to organic thin film transistor as gate dielectric. Deposition rate of over 8.6 nm/min, dielectric constant of 3.4, and leakage current density of 8.9 ×10-9 A/cm-2 at electric field of 1 MV/cm were achieved for the ppMMA thin film prepared at the optimized process condition: plasma power of RF 100 W; Ar flow rate of 20 sccm; working pressure of 5 mTorr; substrate temperature of 100 °C; substrate position of 100 mm. The ppMMA thin film was then applied to pentacene based organic thin film transistor (OTFT) device fabrication. The OTFT device with 80 nm thick pentacene semiconductor layer showed field effect mobility of 0.144 cm2 V-1 s-1 and threshold voltage of -1.72 V.