Plasma Polymerized Thin Films Research Articles

Optical characterization and dispersion analyses of plasma polymerized methyl acrylate thin films

This work reports the structural characteristics, surface morphology, linear and nonlinear optical properties of 110 to 225 nm thick plasma polymerized methyl acrylate (PPMA) thin films. X-ray diffraction analyses confirm the amorphous nature of the films. Field emission scanning electron micrographs of the films display cluster-based surface morphology. Attenuated total reflectance Fourier transform infrared spectroscopy confirms the chemical structural changes in the films. The optical properties were studied based on the absorbance, transmittance, and reflectance spectra measured by an ultraviolet–visible spectrophotometer within the wavelength ranges from 200 to 800 nm. The direct optical band gap and Urbach values are increased from 3.66 to 3.83 eV and 0.28 to 0.45 eV, respectively with increasing film thickness. The extinction coefficient and refractive index were evaluated, and discussed a correlation between the refractive index and the optical bandgap. The real and imaginary dielectric constants, volume/surface energy loss functions and skin depth were deduced. The oscillator energies and parameters were analyzed using the concept of Wemple-DiDomenico and Sellmeier models, respectively for a single oscillator. Static linear refractive index for the studied films exhibits normal dispersion behavior with film thicknesses and satisfied Moss, Ravindra-Gupta, and Herve-Vandamme rules. The linear susceptibility, third-order nonlinear susceptibility and the non-linear refractive index are considerably reduced from 0.20, 29.5 × 10−14 esu, and 5.89 × 10−12 esu with increasing optical band gap energies. The outcomes from the analyses of PPMA demonstrated their potential for usage in electronic, optoelectronic, and non-linear device applications.

Comparison of Plasma-Polymerized Thin Films Deposited from 2-Methyl-2-oxazoline and 2-Ethyl-2-oxazoline: I Film Properties.

Poly(2-oxazoline) is a promising new class of polymeric materials due to their antibiofouling properties and good biocompatibility. Poly(2-oxazoline) coatings can be deposited on different substrates via plasma polymerization, which can be more advantageous than other coating methods. The aim of this study is to deposit poly(2-oxazoline) coatings using a surface dielectric barrier discharge burning in nitrogen at atmospheric pressure using 2-methyl-2-oxazoline and 2-ethyl-2-oxazoline vapours as monomers and compare the film properties. For the comparison, the antibacterial and cytocompatibility tests were peformed according to ISO norms. The antibacterial tests showed that all the deposited films were highly active against Staphylococcus aureus and Escherichia coli bacteria. The chemical composition of the films was studied using FTIR and XPS, and the film surface's properties were studied using AFM and surface energy measurement. The cytocompatibility tests showed good cytocompatibility of all the deposited films. However, the films deposited from 2-methyl-2-oxazoline exhibit better cytocompatibility. This difference can be explained by the different chemical compositions and surface morphologies of the films deposited from different monomers.

Charge carrier transport mechanism in plasma polymerized methyl acrylate thin films

Plasma-polymerized methyl acrylate thin films (PPMA) of thicknesses 115 to 290 nm were prepared using a capacitively coupled glow discharge plasma reactor. The current density-voltage (J-V) characteristics of the Aluminum/PPMA/Aluminum sandwich configuration were studied between 0.1 and 75 V over the temperature region from 298 K to 398 K for various thicknesses of PPMA thin films. J-V curves show that the conduction current follows Ohm's law in the low voltage area, but that in the high voltage range, the behavior is attributed to be space charge-limited conduction (SCLC) in PPMA thin films. The free carrier density, the trap density and carrier mobility have been determined to be around 1.77 × 1023 to 5.86 × 1023 m−3, 2.84 × 1024 to 3.77 × 1024 m−3, and 3.87 × 10−18 to 69.7 × 10−18 m2V−1s−1, respectively for various thicknesses of PPMA thin films. For the higher temperature and lower temperature areas, the activation energies were found in the range from 0.60 to 0.84 eV and 0.28 to 0.40 eV, respectively for 5 V in Ohmic region and from 0.61 to 0.98 eV and 0.27 to 0.34 eV, respectively for 60 V in SCLC (Non-Ohmic) region, respectively. It is observed that SCLC mechanism in PPMA thin films is dominated by a single dominant trap level/discrete trap level distribution. The PPMA thin films are promising candidates in manufacturing optoelectronic devices.

Plasma Polymerized Organosilicon Thin Films for Volatile Organic Compound (VOC) Detection

Plasma polymerized (PP) thin films deposited in a soft or intermediate plasma discharge from hexamethyldisiloxane (HMDSO) were developed as sensors for the detection of volatile organic compound (VOC) vapors. Energy dispersive X-ray spectroscopy (EDX) and X-ray reflectometry (XRR) were performed to determine the organosilicon films’ elemental composition and density. Spectroscopic ellipsometry measurements were carried out to determine the refractive index of the films. Quartz crystal microbalance (QCM) and ellipsometry coupled to vapor sorption were used to investigate the sorption mechanism of several VOC vapors into the films as a function of the plasma deposition conditions. The density and the refractive index of the PP-HMDSO films increased with the plasma energy due to a different chemical composition and different proportion of free volumes in the material network. The PP-HMDSO films showed different affinities towards the VOC vapors depending on the plasma discharge energy. The films elaborated in the lowest plasma energy revealed a good sensitivity towards the VOCs, especially toluene (one of the BTEX vapors), compared to the other films deposited under higher plasma energy. In addition, the selectivity between toluene and other non-BTEX VOCs such as heptane and ethanol decreased to become zero while increasing the plasma energy.

Atmospheric Pressure Plasma Polymerization of Carvone: A Promising Approach for Antimicrobial Coatings

Medical devices are often vulnerable to colonization by nosocomial pathogens (bacteria), leading to infections. Traditional sterilization methods may not always be effective, and as a result, alternative options are being explored to prevent microbial contamination. Recently, scientists are emphasizing using plant-derived essential oils that possess inherent antibacterial properties to produce antimicrobial coatings using plasma polymerization technology carried out at atmospheric pressure (AP). This approach shows promise compared to other coating strategies that need several processing steps, including a high-vacuum system, and are laborious, such as the immobilization of antimicrobial materials on precoated layers in the low-pressure plasma polymerization approach. The present study demonstrates the potential of AP plasma polymerization for producing thin films with excellent antibacterial properties and surface characteristics. The resulting coatings are stable, smooth, and have high wettability, making them ideal for repelling bacteria. The calculated zeta potential and deposition rate for the films are also favorable. These AP plasma-polymerized thin films created from carvone show a reduction rate of more than 90% for Escherichia coli and Staphylococcus aureus bacteria. Our computational docking studies also reveal strong binding interactions between the original carvone monomer and both bacteria. The study suggests that these AP plasma-produced coatings have great potential as antibacterial coatings for biomedical devices.

Enhanced Adhesion of Electrospun Polycaprolactone Nanofibers to Plasma-Modified Polypropylene Fabric.

Excellent adhesion of electrospun nanofiber (NF) to textile support is crucial for a broad range of their bioapplications, e.g., wound dressing development. We compared the effect of several low- and atmospheric pressure plasma modifications on the adhesion between two parts of composite-polycaprolactone (PCL) nanofibrous mat (functional part) and polypropylene (PP) spunbond fabric (support). The support fabrics were modified before electrospinning by low-pressure plasma oxygen treatment or amine plasma polymer thin film or treated by atmospheric pressure plasma slit jet (PSJ) in argon or argon/nitrogen. The adhesion was evaluated by tensile test and loop test adapted for thin NF mat measurement and the trends obtained by both tests largely agreed. Although all modifications improved the adhesion significantly (at least twice for PSJ treatments), low-pressure oxygen treatment showed to be the most effective as it strengthened adhesion by a factor of six. The adhesion improvement was ascribed to the synergic effect of high treatment homogeneity with the right ratio of surface functional groups and sufficient wettability. The low-pressure modified fabric also stayed long-term hydrophilic (ten months), even though surfaces usually return to a non-wettable state (hydrophobic recovery). In contrast to XPS, highly surface-sensitive water contact angle measurement proved suitable for monitoring subtle surface changes.

(Invited) Plasma Technology in Surface Engineering: From Super-Hydrophilic to Super-Hydrophobic Materials

Materials surface wettability is a fundamental property of a solid. Wettability plays a paramount role in the everyday applications of solid materials in many fields of science and technology. Numerous examples include advanced membranes (from water purification to biopharmaceuticals), energy storage devices, windows, raincoats, roofs, disposable diapers, microfluidics, bandages, tissue scaffolds, and bio-implants. With the continuous development of modern society, the demand for advanced functional materials with the desirable surface wettability is increasing faster than ever before. This is why precise control over surface wettability is expected to provide materials with superior properties for unprecedented applications in diverse fields.Over the past decade, conventional wet chemistry approaches have been among the most frequently used methods for surface wettability control. However, they are often energy-inefficient, pollute the environment, and rely on harsh synthesis conditions. Recently, low-temperature plasma processing has attracted major attention in surface wettability control. The reason for this particular interest is because plasma processing is highly-selective, environmentally friendly, and low-cost. Plasma processing can uniquely modify both the surface chemistry and surface topography for a wide range of materials. Moreover, it can be operated at very mild conditions such as room temperature, atmospheric pressure, and open-air environments.Plasma can be used as a controlled reactive physicochemical environment for surface activation, coating deposition, and nanostructuring of diverse materials. The unique plasma-specific conditions and effects allow precise control over microscopic surface chemical composition and surface nanostructures by adjusting the macroscopical energy input. Accordingly, effective control over surface wettability can be achieved for a broad range of hard and soft materials. An environmentally friendly, large scale and low-cost wetting control method that does not result in bulk damage, would result in improvement of industrial applications. A possible solution to this wetting control problem is atmospheric-pressure plasma (APP), especially the plasma generated in open-air due to the benefits of solvent-free treatment, requiring no vacuum systems and suitable for in-line processes. In the current work, we will give a comprehensive overview of different atmospheric pressure plasma processes capable to change the surface properties of the polymers with little or no change of the bulk. Two main approaches: (i) plasma activation introducing oxygen-containing groups into the material surface; (ii) plasma polymerization directed to the change of the surface composition will be highlighted and background will be explained.Recently our team developed a new approach based on the use of a combination of plasma activation and plasma polymerization, two different plasma techniques in a single process to achieve different surface wetting properties from hydrophilic to hydrophobic, with the high long-term stability of the coatings in water. Such a type of research approach realized in one plasma source was not yet applied for wettability control and has very promising application potential in the industrial processing of polymers. For surface engineering, and easy to scale-up the radio frequency (RF) plasma system was adopted to perform both plasma activation and plasma polymerization on PET substrate in the atmospheric pressure in the open air. Different characterization methods including WCA measurements, Fourier-transform infrared spectroscopy (FT-IR), XPS, and atomic force microscopy (AFM) were applied to get an insight into surface chemistry and morphology and the effect of the combination of the plasma activation with plasma polymerization.The developed approach has shown the capability of stable coatings deposition with the use of acrylic acid, HMDSO or fluorine-containing precursors PFDA. We demonstrate a single-step, fast, green, cheap, and universal plasma-based approach with potential for large-scale production of oil/water separation membranes, namely aerosol-assisted plasma deposition (AAPD). A hydrophobic polyester membrane is exposed to an in-line atmospheric pressure plasma coupled with an aerosol of a 2-hydroxyethyl methacrylate (HEMA) monomer. A plasma polymerized HEMA thin film is thus successfully coated on the membrane, resulting in an superhydrophilic/underwater superoleophobic surface. With created coating, the water pre-wetted plasma-functionalized polyester membrane shows an ultrahigh separation efficiency above 97.8% towards various oil/water mixtures and a superb water flux above 35.6 L m-2 s-1. Importantly, it also exhibits excellent performance in anti-oil-fouling, recyclability, and durability, indicating its high potential in real-life usage. To further examine the universality of the proposed approach, another hydrophilic monomer (acrylic acid) is also used to functionalize the polyester membranes. The obtained functionalized membranes can also efficiently separate diversified oil/water mixtures. Therefore, this study demonstrates the capability of plasma-based surface engineering methods to manipulate surface properties of materials in a very wide range from superhydrophobic to hydrophilic and even super-hydrophilic which opens new areas of applications.

Plasma-Polymerized Aniline–Diphenylamine Thin Film Semiconductors

Semiconducting polymer thin films were grown by a DC plasma-polymerized technique using a mixture of aniline–diphenylamine as a precursor. FT-IR spectra were taken in order to analyze the structural properties of the resulting polymers. From morphological and structural studies performed by transmission electron microscope (TEM) and X-ray diffraction, an organized structure in plasma polymer thin films was distinguished. I–V characteristics in an asymmetric electrode configuration were studied to determine the conduction mechanism. It was found that the conduction mechanism controlled by SCLC is dominant in plasma-polymerized aniline–diphenylamine (PPAni-PDPA) thin films.

Plasma-aerosol-assisted surface engineering for scalable oil/water membrane separation

Oily wastewater raises worldwide concerns. Conventional remediation strategies suffer from complex and environmentally unfriendly processes. Herein, we demonstrate an efficient oil/water separation membrane prepared by a green process, namely aerosol-assisted plasma deposition. A hydrophobic polyester membrane is exposed to an in-line atmospheric pressure plasma coupled with an aerosol of a 2-hydroxyethyl methacrylate (HEMA) monomer. A plasma polymerized HEMA thin film is thus coated on the membrane, resulting in superhydrophilic/underwater superoleophobic properties. The water pre-wetted plasma-functionalized polyester membrane shows an ultrahigh separation efficiency above 97.8% towards various oil/water mixtures and a superb water flux above 35.6 L ∙ m−2∙ s−1. It also exhibits excellent performance in anti-oil-fouling, recyclability, and durability. To further examine the universality of the proposed approach, acrylic acid is also used as aerosol to functionalize the polyester membranes. The obtained functionalized membranes can also efficiently separate diversified oil/water mixtures. Furthermore, the fabrication efficiency and energy efficiency of this plasma-based surface engineering method are evaluated, which are approximately 799 cm2/h and 0.81 kW·h/m2, respectively. Therefore, this study offers a highly promising route for engineering of oil/water separation membranes helping to pave the path towards efficient oily wastewater remediation.

Molecular dynamics, transport property, and surface stoichiometry of plasma polymerized cyclohexane thin films

The properties of cyclohexane (CHex) and plasma polymerized cyclohexane (PPCHex) thin films are studied, and the results are compared with those obtained using a computing model (under the density functional theory framework). Quantum chemical calculations are performed to calculate their molecular electrostatic potential (MEP), highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) gaps, thermodynamic stability, chemical reactivity, and vibrational properties. The HOMO–LUMO energy gap sharply decreased in the case of the PPCHex thin film compared to that of CHex. Gibbs free energy shows a similar phenomenon where the enthalpy of PPCHex (formation) is almost six times higher than that of CHex. The computed FTIR spectra indicate good agreement with the experimental results. RMS roughness shows a smooth surface, and it is compared with the FESEM image. Moreover, the dielectric constant and electrical conductivity of the PPCHex thin films are also studied.

The Correlation of Plasma Characteristics to the Deposition Rate of Plasma Polymerized Methyl Methacrylate Thin Films in an Inductively Coupled Plasma System

A plasma system attached with one internal coil (for generating inductively coupled plasma) and two sputtering carbon targets was set up to deposit PP-MMA (plasma polymerized methyl methacrylate) thin films. PP-MMA was used as a model material in the present study. In the experiment, the working pressure and Ar/MMA flow ratio were varied, which resulted in the change in plasma conditions as well as the deposition rates. The optical emission spectroscopy (OES) method was applied to identify the presence of the excited species related to the fragmented monomer. In addition, the electron temperature and electron density were determined using the modified Boltzmann plot and line-ratio method, according to the measured OES spectra. The deposition rate of the PMMA film was then correlated with the determined plasma characteristics. To determine the vibrational modes of the deposited PP-MMA films, Fourier transformed infrared spectrometry (FTIR) was used. The highest deposition rate of PP-MMA could be obtained with the optimized working pressure and Ar/MMA volume ratio. This could be related to the plasma characteristics that contribute to the fragmentation of the monomer in the plasma.

Surface morphology of nanostructured plasma-polymer thin films deposited under dusty plasma conditions

Plasma-polymer thin films were prepared under dusty plasma conditions. Due to their nanocomposite structure, the films showed unique mechanical properties including high elastic recovery resulting in a behaviour similar to superelasticity. The work is mainly focused on the characterization of the films by means of analytical scanning electron microscopy. We observed that variation of the deposition conditions caused substantial changes of surface topography of the deposited films. Consequently, the surface free energy varied in a wide range so it was possible to prepare films with either hydrophilic or hydrophobic properties.

Comparative analysis of hexamethyldisiloxane and hexamethyldisilazane plasma polymer thin films before and after plasma oxidation

AbstractThe presented study compares the structure of hexamethyldisiloxane (HMDSO) and hexamethyldisilazane (HMDSN) plasma polymer thin films with a thickness of about 30 nm before and after a plasma oxidation process, focusing on the analysis of porosity and the correlated electrolyte up‐take in the formed films. The results illustrate that the plasma oxidation treatment converts the HMDSO and HMDSN plasma polymer films progressively into SiOx‐like films. However, the underlying mechanism of the etching of CxHy groups and the condensation of intermediate Si‐OH groups leads to highly porous films. The studies show that the differences in the chemical structure and nanoporosity as measured by spectroscopic techniques could be correlated with the resulting up‐take of electrolytes in the open pores of the films.

Comparative Study on the Direct Current Electrical Conduction in Monolayer and Bilayer Plasma Polymerized Thin Films

A comparative study on the nature of direct current electrical conduction in the monolayer and bilayer plasma polymerized thin films has been discussed in this article. The plasma polymerized pyrrole (PPPy) monolayer, plasma polymerized N,N,3,5-tetramethylaniline (PPTMA) monolayer and plasma polymerized pyrrole-N,N,3,5-tetramethylaniline (PPPy-PPTMA) bilayer thin films were deposited at room temperature onto glass substrates by using a parallel plate capacitively coupled glow discharge reactor. The current density-voltage (J-V) characteristics and the conductivity-voltage (σ-V) characteristics have been studied to analyze the direct current conduction mechanism in PPPy, PPTMA monolayer and PPPy-PPTMA bilayer thin films. The observed results have been presented in this paper. The J-V and σ-V characteristics of PPPy and PPTMA monolayer thin films of different thicknesses indicated an increase in electrical conduction and also an increase in conductivity in the films of lower thicknesses. It is also observed that PPTMA thin films are more conductive than that of PPPy thin films. As a result the PPPy-PPTMA bilayer thin films of different thicknesses and different deposition time ratios indicated an increase in conductivity as the proportion of PPTMA is increased in the films. In addition to that, from the J-V and σ-V characteristics of PPPy, PPTMA and PPPy-PPTMA thin films of same thickness, it is observed that the current conduction and the conductivity in the bilayer thin films is less compared to the monolayer thin films. This unusual result has been explained by studying ideal and real bilayer thin films. It is also seen that in the low voltage region, the current conduction obeys Ohm’s law while the charge transport phenomenon appears to be the space charge limited conduction (SCLC) in the higher voltage regions.

Thickness dependent thermal and optical properties of plasma polymerized N-benzylaniline thin films

Thermally stable, smooth and highly transparent plasma polymerized (N-benzylaniline) thin films are deposited onto glass substrates under ac (50 Hz) glow discharge plasma. Thermal stability and optical absorbance of the films are very high, indicate conjugation in the films, which depends on their thickness. Other optical parameters such as band energy gaps, steepness, Urbach energy, dielectric constant, etc. are also observed to vary with film thickness. The small value of extinction coefficient and high value of refractive index confirms that the films are very smooth highly transparent, and therefore suitable for anti-reflecting coating and infrared applications.

Comparative study of bulk and surface compositions of plasma polymerized organosilicon thin films

Plasma polymerized organosilicon thin films were deposited in a MW-PECVD using hexadimethylsiloxane (HMDSO) as a precursor. Thin films were synthetized with different plasma conditions ranging from soft (low plasma energy) to hard (high plasma energy) ones. Quantitative 29Si solid state NMR and FTIR spectroscopy were used to characterize the bulk composition. X-ray photoelectron spectroscopy (XPS) coupled with Density Functional Theory (DFT) calculations were used to determine the surface chemical composition. In addition, water contact angle (WCA) measurements were performed in order to complete the surface characterization. The bulk and the surface of the plasma polymerized HMDSO (PP-HMDSO) showed a complex chemical composition. The four main environments M, D, T and Q were present in the films. An additional environment Si(CH2)(CH3)3 denoted S was detected in the PP-HMDSO films. The chemical composition comparison showed a difference between the bulk and the surface of the films. Under soft plasma conditions, a high amount of SiOC3 termination was present in the bulk of the films. While, the SiO2C2 chains were highly present on the surface. On the other hand, under hard plasma conditions, the number of the SiOC3 termination increased on the surface and decreased in the bulk. Under soft plasma conditions, the PP-HMDSO structure was close to PDMS, while under hard plasma conditions, the PDMS similarity was lost.

Thickness dependent structural and surface properties of plasma polymerized N-benzylaniline thin films

Thickness dependent structural, surface morphological, topographical and compositional studies have been done on the plasma polymerized N-benzylaniline (PPNBA) thin films, where the plasma is obtained by a parallel plate capacitively coupled glow discharge system under AC of frequency 50 Hz. From the X-ray diffraction studies, it is confirmed that the PPNBA thin films are amorphous in nature. The chemical structure of the PPNBA films is moderately changed from that of the monomer owing to the elimination of some benzyl groups, however, becomes conjugated due to C=C stretching of the quinoid and benzenoid units. The PPNBA films contain mostly carbon and nitrogen, which is confirmed by the energy-dispersive X-ray analysis. However, the presence of oxygen is considered to be incorporated from the reactor atmosphere. The surface morphologies of the PPBNA thin films of various thicknesses are mosaic-like structure, which is formed by the uniform distribution of unequal nanosized clusters over the smooth background of the film surface. The average roughness and root mean square roughness of the surface of the PPNBA thin films are found to be in the order of pm. The increase in the surface roughness is compatible with the increase in the cluster density, which is evidenced in the field-emission scanning electron microscopy observations.

Characterization of Thin Films Deposited from Benzene Using Microwave Plasma Polymerization

Microwave plasma enhanced chemical vapor deposition (MWPECVD) is a cheap and easy method for the modification of materials surfaces to enhance some required property. In this study, benzene as a monomer was deposited on both Aluminum alloy (2024-T3) and glass slide substrates at several pressures and deposition times using MWPECVD. The chemical structure and surface properties of as-grown thin films were analyzed on glass using FTIR and NMR. It is found that benzene rings are not fully preserved in the film structure. Some benzene rings were converted to saturated alcohol and/or ester functional groups in the crosslinked film structure. The corrosion resistance of aluminum alloy substrates both bare and covered with plasma polymerized thin films was carried out by potentiodynamic polarization measurements in standard 3.5% NaCl solution at room temperature. The benzene deposited film was found to be not fully suitable for protection of aluminum substrate against corrosion. The only film that stayed intact post the corrosion measurement is that for the deposition condition of 30 mtorr for 90 minutes. The change in the processing parameters seemed to have a strong influence on the film protective ability. SEM was used to study the surface morphology of deposited films on aluminum. It is found that the polymerized film roughness decreases with increasing monomer pressure and deposition time. Adhesion test done on films deposited on glass showed that the best adhesion occurs for deposition condition of 30 mtorr for 90 minutes and poor adhesion occurred at 7 and 9 mtorr for 90 minutes.

Photovoltaic performance of non-covalent functionalized single-layer graphene in dye-sensitized solar cells (DSSCs)

In this study, it was aimed to fabricate new effective alternative counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). For this purpose, firstly, single-layer graphene (SLG) thin films were grown by chemical vapor deposition (CVD) method. Then, these films were separately functionalized with 1,8-cineole (ppCin/SLG), D-Limonene (ppLim/SLG) and Thiophene (ppTh/SLG) by plasma polymerization. Number of layers in CVD-grown graphene determined by Raman, transmission electron microscope (TEM) and ultraviolet–visible (UV–Vis) spectroscopy. Chemical structures of plasma polymerised (pp) thin films were investigated by Fourier transform infrared (FTIR) spectroscopy. Photovoltaic parameters of DSSCs were calculated, and electrocatalytic properties of CEs were investigated by electrochemical impedance spectroscopy (EIS). Polymer functionalization greatly enhanced the electrical conductivity and electrocatalytic activity properties of graphene compared to that of SLG. The efficiencies of DSSCs with ppCin/SLG and ppLim/SLG CEs were 1.10% and 1.02%, respectively. As a result, the cell efficiencies of ppCin/SLG and ppLim/SLG could be as alternative materials to platinum (Pt) counter electrode.

When chemistry of the substrate drastically controls morphogenesis of plasma polymer thin films

AbstractThe impact of surface chemistry on the morphogenesis of maleic anhydride plasma polymer is investigated on silicon wafers with very well‐controlled surface chemistries (i.e., native oxide, hydroxyl‐rich, and alkyl‐rich). A particular attention is paid to characterize the early stages of growth. Two different morphologies of polymer films are obtained, depending on the hydrophilic or hydrophobic nature of the substrate surface, even though the chemical composition is very similar. Homogeneous and dense polymer films are formed on hydrophilic substrates due to the strong affinity of plasma species toward the surface. Elongated nanostructures resulting in a less dense polymer film grow on the hydrophobic surface, which are assumed to be the result of the low affinity of plasma species.