Plasma Polymerized Thin Films Research Articles

Atmospheric pressure plasma polymerization using double grounded electrodes with He/Ar mixture

In this study, we have proposed the double grounded atmospheric pressure plasma jet (2G-APPJ) device to individually control the plasmas in both fragmentation (or active) and recombination (or passive) regions with a mixture of He and Ar gases to deposit organic thin films on glass or Si substrates. Plasma polymerization of acetone has been successfully deposited using a highly energetic and high-density 2G-APPJ and confirmed by scanning electron microscopy (SEM). Plasma composition was measured by optical emission spectroscopy (OES). In addition to a large number of Ar and He spectra lines, we observed some spectra of C2 and CH species for fragmentation and N2 (second positive band) species for recombination. The experimental results confirm that the Ar gas is identified as a key factor for facilitating fragmentation of acetone, whereas the He gas helps the plume of plasma reach the substrate on the 2nd grounded electrode during the plasma polymerization process. The high quality plasma polymerized thin films and nanoparticles can be obtained by the proposed 2G-APPJ device using dual gases.

Ion irradiation as a tool for modifying the surface and optical properties of plasma polymerised thin films

Radio frequency (R.F.) glow discharge polyterpenol thin films were prepared on silicon wafers and irradiated with I10+ ions to fluences of 1×1010 and 1×1012ions/cm2. Post-irradiation characterisation of these films indicated the development of well-defined nano-scale ion entry tracks, highlighting prospective applications for ion irradiated polyterpenol thin films in a variety of membrane and nanotube-fabrication functions. Optical characterisation showed the films to be optically transparent within the visible spectrum and revealed an ability to selectively control the thin film refractive index as a function of fluence. This indicates that ion irradiation processing may be employed to produce plasma-polymer waveguides to accommodate a variety of wavelengths. XRR probing of the substrate-thin film interface revealed interfacial roughness values comparable to those obtained for the uncoated substrate’s surface (i.e., both on the order of 5Å), indicating minimal substrate etching during the plasma deposition process.

Organo-Chlorinated Thin Films Deposited by Atmospheric Pressure Plasma-Enhanced Chemical Vapor Deposition for Adhesion Enhancement between Rubber and Zinc-Plated Steel Monofilaments.

A continuous-flow plasma process working at atmospheric pressure is developed to enhance the adhesion between a rubber compound and a zinc-plated steel monofilament, with the long-term objective to find a potential alternative to the electrolytic brass plating process, which is currently used in tire industry. For this purpose, a highly efficient tubular dielectric barrier discharge reactor is built to allow the continuous treatment of "endless" cylindrical substrates. The best treatment conditions found regarding adhesion are Ar/O2 plasma pretreatment, followed by the deposition from dichloromethane of a 75 nm-thick organo-chlorinated plasma polymerized thin film. Ar/O2 pretreatment allows the removal of organic residues, coming from drawing lubricants, and induces external growth of zinc oxide. The plasma layer has to be preferably deposited at low power to conserve sufficient hydrocarbon moieties. Surface analyses reveal the complex chemical mechanism behind the establishment of strong adhesion levels, more than five times higher after the plasma treatment. During the vulcanization step, superficial ZnO reacts with the chlorinated species of the thin film and is converted into porous and granular bump-shaped ZnwOxHyClz nanostructures. Together, rubber additives diffuse through the plasma layer and lead to the formation of zinc sulfide on the substrate surface. Hence, two distinct interfaces, rubber/thin film and thin film/substrate, are established. On the basis of these observations, hypotheses explaining the high bonding strength results are formulated.

Growth kinetics of plasma-polymerized films.

The growth kinetics of polymer thin films prepared by plasma-based deposition method were explored using atomic force microscopy. The growth behavior of the first layer of the polythiophene somewhat differs from that of the other layers because the first layer is directly deposited on the substrate, whereas the other layers are deposited on the polymer itself. After the deposition of the first layer, each layer is formed with a cycle of 15 s. The present work represents the growth kinetics of the plasma-polymerized films and could be helpful for further studies on growth kinetics in other material systems as well as for applications of plasma-polymerized thin films.

Detailed investigation of optoelectronic and microstructural properties of plasma polymerized cyclohexane thin films: Dependence on the radiofrequency power

Optical properties of polymerized cyclohexane films deposited by radiofrequency plasma enhanced chemical vapor deposition technique at different radiofrequency powers onto glass and silicon substrates, are studied and correlated with the microstructure of the films, using a combination of atomic force microscopy, Raman and Fourier Transformer Infrared spectroscopy and optical measurements. The optical constants such as refractive index n, dielectric permittivity ε and extinction k and absorption α coefficients, are extracted from transmission and reflection spectra through the commercial software CODE. These constants lead, by using common theoretical models as Cauchy, Lorentz, Tauc and single effective oscillator, to the determination of the static refractive index ns and permittivity εs, the plasma frequency ωp, the carrier density to effective mass ratio N/me*, the optical conductivity σoc, the optical band gap Eg and the oscillation and dispersion energies E0 and Ed, respectively. We find that n, εs, ωp, N/me*, Ed, increase with radiofrequency power, while Eg and E0 decrease in the same range of power. These results are well correlated with those obtained from atomic force microscopy, Raman and infrared measurements. They also indicate that the increase of the radiofrequency power promotes the fragmentation of the precursor and increases the carbon C-sp2 hybridization proportion, which results in an improvement of the optoelectronic properties of the films.

Mechanical, Optical and Barrier Properties of PLA-layered Silicate Nanocomposites Coated with Organic Plasma Polymer Thin Films

Mechanical, Optical and Barrier Properties of PLA-layered Silicate Nanocomposites Coated with Organic Plasma Polymer Thin Films

Achieving enhanced material finishing using cold plasma treatments

Plasma processing treatments are used widely in materials finishing. The plasmas used for these applications can be either ‘hot’ or ‘cold’. Examples of the former include those used in thermal spray and arc discharge machining. Cold plasmas, which are the focus of this review, are used for relatively low temperature surface cleaning and polymer activation. Cold plasmas can also be used for the deposition of coatings including plasma polymerised thin films. These nanometre thick polymer layers exhibit a tailored chemical functionality and can be used, for example, to control surface wetting properties ranging from superhydrophilic to superhydrophobic (SH). These cold plasmas can be operated under both low pressure and atmospheric conditions. Commercial materials finishing applications of ‘cold’ plasma treatments are highlighted.

Electrical conduction in plasma polymerized thin films of γ‐terpinene

ABSTRACTPlasma polymerized γ‐terpinene (pp−GT) thin films are fabricated using RF plasma polymerization. MIM structures are fabricated and using the capacitive structures dielectric properties of the material is studied. The dielectric constant values are found to be in good agreement with those determined from ellipsometric data. At a frequency of 100 kHz, the dielectric constant varies with RF deposition power, from 3.69 (10 W) to 3.24 (75 W). The current density–voltage (J−V) characteristics of pp–GT thin films are investigated as a function of RF deposition power at room temperature to determine the resistivity and DC conduction mechanism of the films. At higher applied voltage region, Schottky conduction is the dominant DC conduction mechanism. The capacitance and the loss tangent are found to be frequency dependent. The conductivity of the pp−GT thin films is found to decrease from 1.39 × 10−12 S/cm (10 W) to 1.02 × 10−13 S/cm (75 W) and attributed to the change in the chemical composition and structure of the polymer. The breakdown field for pp–GT thin films increases from 1.48 MV/cm (10 W) to 2 MV/cm (75 W). A single broad relaxation peak is observed indicating the contribution of multiple relaxations to the dielectric response for temperature dependent J−V. The distribution of these relaxation times is determined through regularization methods. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42318.

Organic Thin Film Transistors with Gate Dielectrics of Plasma Polymerized Styrene and Vinyl Acetate Thin Films

Organic polymer dielectric thin films of styrene and vinyl acetate were prepared by the plasma polymerization deposition technique and applied for the fabrication of an organic thin film transistor device. The structural properties of the plasma polymerized thin films were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, atomic force microscopy, and contact angle measurement. Investigation of the electrical properties of the plasma polymerized thin films was carried out by capacitance-voltage and current-voltage measurements. The organic thin film transistor device with gate dielectric of the plasma polymerized thin film revealed a low operation voltage of −10V and a low threshold voltage of −3V. It was confirmed that plasma polymerized thin films of styrene and vinyl acetate could be applied to functional organic thin film transistor devices as the gate dielectric.

Photothermal study of RF-plasma polymerized hexamethyldisilazane thin films

Plasma polymerization by RF excited low pressure plasmas is a powerful technique for synthesizing thin films for a wide range of applications such in microelectronics, biomaterials and aeronautical industries. Among these applications plasma polymerized hexamethyldisilazane (HMDSN here in) is a promising material due its biocompatibility, optical and electrical properties. In the present paper, we reported the thermal diffusivity measurements of plasma polymerized HMDSN thin films using the probe beam deflection technique (PBD). The samples are thermally thin and optically transparent, with thicknesses ranging from 170 to 600nm, difficulting their thermal characterization by other photo-thermal techniques (photoacoustic and pyroelectric). PBD measurements were carried out with a diode (20mW, λ=640nm) and a HeNe (0.9mW, λ=632nm) laser, used as pump source and probe beam, respectively. The probe beam was focused close to the sample surface and its direction was perpendicular to the pump beam. The transverse PBD in skimming configuration is employed and the deflection signal is analyzed using the phase method for the determination of thermal diffusivity. The results show the decreasing of thermal diffusivity with the decreasing of film thickness. HMDSN film׳s thermal diffusivity values are reported in this paper for the first time being in the range of typical polymeric samples.

Long-range surface plasmon resonance sensors fabricated with plasma polymerized fluorocarbon thin films

A rapid and simple approach to prepare the dielectric buffer layers is of crucial importance for the development of long-range surface plasmon resonance (LRSPR) sensors. In this regard, we describe for the first time the use of plasma polymerized fluorocarbon thin films as the dielectric buffer layers for the construction of LRSPR sensors. The fluorocarbon films were achieved by radio frequency plasma polymerization of perfluorooctyl ethylene (PFOE) at continuous wave mode with an input power of 60 Watts. The resulting ppPFOE exhibited good adhesion with both the glass substrate and the gold superstrate, and also remained relatively stable in aqueous solutions as seen by optical waveguide spectroscopy (OWS). The obtained LRSPR sensor consisting of a SF11-ppPFOE-Au structure was employed for the detection of both the bulk refractive index variation and the protein adsorption.

Deposition of Fluorine-Containing Thin Film by Atmospheric Pressure Plasma Jet and Film Surface Structural Transition

Plasma polymerized fluorine-containing (SiOxCyFz) thin films were deposited with an atmospheric pressure plasma jet, a useful technique to form thin films of fluorocarbon/silica nanohybrids. This atmospheric pressure plasma polymerization was fed with argon/1H,1H,2H,2H-perfluorooctyltriethoxysilane mixtures. AFM analysis found the nano-textured SiOxCyFz thin films obtained a high degree of surface roughness with an average size of 30 nm. FTIR and XPS found varying working distances in their chemical structure transitions. As the working distance increased, the fluorine compositions of the SiOxCyFz films increased from 12 to 50%, and at a greater working distance, the chemical structure of the atmospheric pressure plasma polymerized thin films was converted to the fluorine-containing dominion. The dielectric constant property of the SiOxCyFz thin film was examined by ellipsometry. From experimental results indicated, the decrease in the dielectric constant of the SiOxCyFz thin films can be attributed a decreased electronic polarization. This investigation demonstrates that the working distance of atmospheric pressure plasma polymerization affords good control of fluorine-containing film properties.

Immobilization and controlled release of drug using plasma polymerized thin film

In this study, plasma polymerization of acrylic acid was employed to immobilize drug and control its release. Doxorubicin (DOX) was immobilized covalently on the glass surface deposited with plasma polymerized acrylic acid (PPAAc) thin film containing the carboxylic group. At first, the PPAAc thin film was coated on a glass surface at a pressure of 1.33Pa and radio frequency (RF) discharge power of 20W for 10min. DOX was immobilized on the PPAAc deposition in a two environment of phosphate buffer saline (PBS) and dimethyl sulfoxide (DMSO) solutions. The DOX immobilized surface was characterized by scanning electron microscope, atomic force microscope and attenuated total reflection Fourier transform infrared spectroscopy. The DOX molecules were more immobilized in PBS than DMSO solution. The different immobilization and release profiles of DOX result from the solubility of hydrophobic DOX in aqueous and organic solutions. Second, in order to control the release of the drug, PPAAc thin film was covered over DOX dispersed layer. Different thicknesses and cross-linked PPAAc thin films by adjusting deposition time and RF discharge power were covered on the DOX layer dispersed. PPAAc thin film coated DOX layer reduced the release rate of DOX. The thickness control of plasma deposition allows controlling the release rate of drug.

Wetting, Solubility and Chemical Characteristics of Plasma-Polymerized 1-Isopropyl-4-Methyl-1,4-Cyclohexadiene Thin Films

Investigations on the wetting, solubility and chemical composition of plasma polymer thin films provide an insight into the feasibility of implementing these polymeric materials in organic electronics, particularly where wet solution processing is involved. In this study, thin films were prepared from 1-isopropyl-4-methyl-1,4-cyclohexadiene (γ-Terpinene) using radio frequency (RF) plasma polymerization. FTIR showed the polymers to be structurally dissimilar to the original monomer and highly cross-linked, where the loss of original functional groups and the degree of cross-linking increased with deposition power. The polymer surfaces were hydrocarbon-rich, with oxygen present in the form of O–H and C=O functional groups. The oxygen content decreased with deposition power, with films becoming more hydrophobic and, thus, less wettable. The advancing and receding contact angles were investigated, and the water advancing contact angle was found to increase from 63.14° to 73.53° for thin films prepared with an RF power of 10 W to 75 W. The wetting envelopes for the surfaces were constructed to enable the prediction of the surfaces’ wettability for other solvents. The effect of roughness on the wetting behaviour of the films was insignificant. The polymers were determined to resist solubilization in solvents commonly used in the deposition of organic semiconducting layers, including chloroform and chlorobenzene, with higher stability observed in films fabricated at higher RF power.

Comparative study of structural and optical properties of pulsed and RF plasma polymerized aniline films

Abstract Plasma polymerization of aniline is carried out by means of continuous RF and pulsed DC glow discharge plasma in a common reactor at different applied powers. The discharge control variables are optimized for good quality film growth and the role of fragmentation of the molecular structure on the structural, optical, morphological and optophysical properties of the deposited plasma polymerized aniline (PPAni) layers is investigated. Retention of the conjugated structure is found to be prominent at optimum applied power to the plasma in both the continuous RF and pulsed DC polymerization techniques. Improvement in conjugated structure and chain length have been observed in both the continuous RF and pulse DC PPAni thin films with the increase in applied power to the plasma up to a certain limit of applied power when working pressure is fixed at 0.15 mbar. A decrease in optical bandgap with the increase in applied power to the plasma is observed in both the pulsed DC and RF PPAni thin films, but it is more significant in case of RF PPAni films. The plasma polymerized aniline thin films are found to emit photoluminescence due to band to band transition and defects generated in the structure.

Effect of the defects on the optical and electronic properties of plasma polymerized organic thin films

The microstructure and electronic properties of plasma-polymerized thin films grown by the plasma enhanced chemical vapor deposition (PECVD) method using the cyclohexane as precursor gas are investigated as a function of the radiofrequency power. Infrared, Raman and optical transmission measurements, correlated with electron paramagnetic resonance ones, are applied to characterize the films in their as-deposited state. The results indicate that increasing the radiofrequency power induces a decrease of the total bonded hydrogen content, accompanied by an increase of the carbon C-sp2 hybridization proportion. A decrease of the optical gap, with increasing radiofrequency power also occurs, and might suggest an increasing overlapping of the Gaussian π–π* bands around the Fermi level. Simultaneously, an increase of the spin density is observed in the same range of the radiofrequency power, suggesting that most of the spins originate from C-sp2 complexes.

Synthesis of N-doped Ethylcyclohexane Plasma Polymer Thin Films with Controlled Ammonia Flow Rate by PECVD Method

In this study, we investigated the basic properties of N-doped ethylcyclohexene plasma polymer thin films that deposited by radio frequency (13.56 MHz) plasma-enhanced chemical vapor deposition (PECVD) method with controlled ammonia flow rate. Ethylcyclohexene was used as organic precursor with hydrogen gas as the precursor bubbler gas. Additionally, ammonia (NH₃) gas was used as nitrogen dopant. The as-grown polymerized thin films were analyzed using ellipsometry, Fourier-transform infrared [FT-IR] spectroscopy, UV-Visible spectroscopy, and water contact angle measurement. We found that with increasing plasma power, film thickness is gradually increased while optical transmittance is drastically decreased. However, under the same plasma condition, water contact angle is decreased with increasing NH₃ flow rate. The FT-IR spectra showed that the N-doped ethylcyclohexene plasma polymer films were completely fragmented and polymerized from ethylcyclohexane.

A Mechanistic Study of the Plasma Polymerization of Ethanol

Plasma polymer thin films are useful in a variety of different fields. In this article, the fragmentation of ethanol during plasma polymerization at different discharge powers (2–32 W) is described. The positive ion mass spectrometry data of the plasma phase demonstrated formation of oligomeric species of the type [M+H]+, [2M+H]+, [3M+H]+, and [4M+H]+. At the same time, there was abundant fragmented species most dominant being ethylene C2H4, acetylene C2H2, water H2O, and hydrogen H2. X‐ray photoelectron spectroscopy was used to relate the mass spectroscopy data of the plasma to the chemistry of the deposited films. Depletion of oxygen in the deposit correlated with greater fragmentation in the plasma phase at higher plasma power.

RF plasma polymerised thin films from natural resources

Plasma polymerisation is an effective tool for fabrication of thin films from volatile organic monomers. RF plasma assisted deposition is used for one-step, chemical-free polymerisation of nonsynthetic materials derived directly from agricultural produces. By varying the deposition parameters, especially the input RF power, the film properties can be tailored for a range of uses, including electronics or biomedical applications. The fabricated thin films are optically transparent with refractive index close to that of glass. Given the diversity of essential oils, this paper compares the chemical and physical properties of thin films fabricated from several commercially exploited essential oils and their components. It is interesting to note that some of the properties can be tailored for various applications even though the chemical structure of the derived polymer is very similar. The obtained material properties also show that the synthesised materials are suitable as encapsulating layers for biodegradable implantable metals.

Influence of the radio-frequency power on the physical and optical properties of plasma polymerized cyclohexane thin films

We investigate in the present study the effects of the radio-frequency plasma power on the opto-electronical properties of the polymeric amorphous hydrogenated carbon thin films deposited at room temperature and different radio-frequency powers by plasma-enhanced chemical vapor deposition method using cyclohexane as precursor. A combination of U.V.–Visible and infrared transmission measurements is applied to characterize the bonding and electronic properties of these films. Some film properties namely surface roughness, contact angle, surface energy, and optical properties are found to be significantly influenced by the radio-frequency power. The changes in these properties are analyzed within the microstructural modifications occurring during growth.