Water-repellent Thin Films Research Articles

Analysis of nano-cluster formation in the PECVD process

In this paper, the ultra water-repellent thin films were prepared by RF PECVD. On the basis of surface morphology, chemical bonding states and plasma diagnostics, a formation model of clusters for the ultra water-repellent films was discussed from considerations of formation process and laser scattering results. Moreover, using laser scattering method, the relative change of quantity of nano-clusters or size of agglomerates could be confirmed. From the results, the films were deposited with nano-clusters and those of agglomerates, which formed in organosilicon plasma, and formation of agglomerates were depended on the deposition time.

Production of Low Electron Temperature Plasma and Coating of Carbon-Related Water-Repellent Films on Plastic Plate

Low electron temperature plasma with a value less than 2 eV was produced by the inductively coupled discharge with a three-turn spiral antenna and the radio-frequency-biased grid for hard coating of carbon-related water-repellent thin films on plastic plate. It was found that the electron temperature decreased with increasing a negative biasing voltage V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> for V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> <; -100 V and, then, electron population becomes bicomponent with the higher temperature of about 10 eV and the lower temperature of less than 2 eV. The water-repellent thin films were also prepared on polycarbonate and silicon wafer substrates in the low electron temperature plasma using C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and Ar mixture gases. The wetting contact angle and the pencil hardness were discussed.

Formation of SiO:CH Ultra Water Repellent Thin Films by Inductively Coupled RF PECVD

In this paper, the UWR thin films were prepared by RF PECVD. The relationships between the deposition conditions and the film properties such as morphological and chemical properties of the films were discussed. Moreover, from the analysis of plasma diagnostics using OES, formation mechanism of UWR thin films was discussed.

Preparation of Water-Repellent Thin Film with Inductive Plasma using C&lt;sub&gt;2&lt;/sub&gt;H&lt;sub&gt;2&lt;/sub&gt;F&lt;sub&gt;2&lt;/sub&gt;/Ar gases and Investigation of Its Adhesion by Positively Pulse-Biasing

Preparation of Water-Repellent Thin Film with Inductive Plasma using C&lt;sub&gt;2&lt;/sub&gt;H&lt;sub&gt;2&lt;/sub&gt;F&lt;sub&gt;2&lt;/sub&gt;/Ar gases and Investigation of Its Adhesion by Positively Pulse-Biasing

Preparation of water-repellent thin film by RF pulse-modulated plasma CVD using C2H2F2 gas

The influences of pulse modulation on water-repellent film preparation have been investigated in RF pulse-modulated plasma CVD using C2H2F2 and Ar mixture gases for an improvement of transparency with keeping repellency. In the case of high total pressure of 100 Pa, transparency of the prepared films decreased from 90 to 50% with increasing duty ratio of RF power, while the water contact angle increased from 120 to 160°. On the other hand, in the case of low-pressure of 25 Pa, these properties of the prepared films were almost independent on the duty ratio, keeping high transparency with more than 90% and normal hydrophobic nature with the contact angle of about 100°.

ＰＥＣＶＤ法による超はっ水薄膜の作製とその形成過程の観察

Ultra water-repellent films were prepared by using rf PECVD. Relationships between the rf power and water repellency, morphological and chemical properties were investigated. Moreover, the growth process of ultra water repellent thin films was evaluated by using FESEM. The experimental results showed that surface morphology of the films strongly depends on the rf power, and that increasing the rf power made it possible to from ultra water-repellent films. At the first stage of the growth, the nano-clusters were deposited randomly on the substrate surface. These clusters were originated from a polymerization process in the gas phase and deposited on the substrate. When the film was deposited for several tens of seconds, the nano-clusters showed a tendency to form chains or islands, which means the clusters must have a spatial preference. Finally, these films have particular nano-textures with nano-scale pores of a few hundreds of nanometers in diameter among the rough web-like structure of the nano-cluster agglomerates

Dynamic Plasma CVD and Preparation of Functional Organic Thin Films

This paper describes the chemical and morphological properties of super water-repellent surface of solid materials prepared by a 13.56 MHz inductively coupled plasma using fluorohydrocarbons such as vinylidene fluoride and 1, 1, 1, 2-tetrafluoroethane. Through the reaction initiated by the electron impact into fluorohydrocarbon molecules, fluorine-containing and hydrophobic polymers grew in the gas phase to deposit on substrates. The morphology of deposits seems to depend on hydrophilicity or hydrophobicity of substrates. The more hydrophilic substrate may maintain the smaller granular structure than ca. 100-nm diam. However, polymer granules may be expanded radially by surface tension and get into flat on hydrophobic substrates. Dynamic plasma CVD we proposed enabled us to control the size of deposited granules on the surface to be smaller and improve the fluorine content to be richer. Thus, we could easily obtain super water-repellent thin film with gradation in granular size and chemical compositions.

Water-repellent thin films from mixtures of fluoroalkylmethoxysilane and bis-(trialkoxysilyl)alkanes of various carbon-chain lengths using the sol–gel method and the fluoroalkylmethoxysilane dispersion mechanism

Water-repellent thin films were fabricated on silicon or germanium wafers by spin-coating sol mixtures of fluoroalkyalkoxysilane (FAS) and bis-(trialkoxysilyl)alkanes with various carbon-chain lengths (Cn: (C2H5O)3Si(CH2)nSi(OC2H5)3, and Cf: (CH3O)3SiC2H4(CF2)6C2H4Si(OCH3)3; n=1, 2, and 8. C0 is defined as Si(OC2H5)4). Before heat treatment, the contact angle of hexadecane on the films increased in the order Cf, C1, C0, C2 and C8 when the FAS concentration in the sol mixture was above 5 mmol/l. With heat treatment higher than 70 °C, the contact angles on the films decreased and the longer the carbon-chain lengths of Cn and Cf the greater the decrease. We show that during spin-coating of the Cn films, FAS accumulates on the outer surface of the film. In Cn films, with n=0, separation of FAS is governed by the repulsion between the non-polar and polar chemical groups while with n≧1, separation is governed by repulsion between the fluoroalkyl-chains and the alkyl-chains. It is speculated that heat treatment causes FAS evaporation, which increases as the carbon-chain length of Cn or Cf increases, owing to the differences in their readiness to undergo hydration.

Water-Repellent Thin Film with High Alkali Resistance Using the Sol–Gel Method for Ink Jet Printer Head

Water-repellent thin films from silane coupling agents have been widely used for inducing hydrophobicity on various surfaces. However, films obtained by conventional methods have poor durability against alkaline solutions. A new water-repellent thin film with high alkali resistance has been obtained for the first time by the sol–gel method using fluoroalkylmethoxysilane and 1,4-bis(trimethoxysilylethyl)benzene (BTB). The film maintained its hydrophobicity after soaking in alkaline ink with pH=8.9 at 70°C for 500 h. While the film maintained alkali resistance after being heat-treated at temperatures up to 300°C, that heat-treated at 400°C lost its alkali resistance. Fourier transform infrared measurements of the film indicated that ethyl groups in BTB molecules burn or oxidize at 400°C. It is speculated that the ethyl groups in the vicinity of siloxane bonds and the three-dimensional BTB polymer network prevent OH-ions from approaching and breaking the siloxane bonds in the film, and thus the film has high alkali resistance. We demonstrate that the new water-repellent film is applicable to the ink jet printer head.

Characteristics of ultra water-repellent thin films prepared by combined process of microwave plasma-enhanced CVD and oxygen-plasma treatment

Transparent thin films with ultra water-repellency were prepared by a combined process of microwave plasma-enhanced CVD (MPECVD) and oxygen-plasma treatment. An organosilicon compound was used as a raw material for MPECVD. Mechanical properties, that is, hardness and wear resistance, of the ultra water-repellent thin films prepared by the combined process were improved in comparison with the films prepared by MPECVD without the oxygen-plasma treatment. The optical performance of the films remained unchanged.

Coating of transparent water-repellent thin films by plasma-enhanced CVD

Transparent water-repellent thin films are prepared by rf and microwave plasma-enhanced CVD (PECVD) methods using organosilicon compounds and fluoro-alkyl silanes (FASs) as source gases. First we prepare the water-repellent films by using three kinds of FASs by rf PECVD. The obtained contact angles depend on the length of perfluoro-alkyl groups (-C n F 2 n + 1 − , n = 1, 6 and 8) in FASs. The maximum contact angle is about 108° which is comparable to that for polytetrafluoroetylene (PTFE). Next we prepare the water-repellent films by mixing FAS and trimethylmetoxysilane (TMMOS) using microwave PECVD. The films consist of silicon oxide containing CF and SiCH 3 bonds and has high water repellency. The fluorine concentration at the surface does not relate directly to the contact angle. The films prepared by both PECVD methods are transparent in the visible region. PECVD is a suitable technique to prepare transparent water-repellent thin films at low substrate temperatures (below 100°C.