Thin films plasma-polymerized coatings

Overcoats are an integral part of thin-film disk structures. Their primary role is to provide wear protection. The most common overlayers, such as Rh, plasma-polymerized coatings, SiOz, and carbon, are all chemically stable if they were fully to cover the disk surface, they would provide good corrosion resistance. The thinness of the overcoats and the roughness of the surface preclude perfect coverage and open up the path for localized corrosion at the sites where the magnetic layer is exposed to the environment. 

Multiphase composites formed of polymer substrates coated with thin metal films show special properties and are in great demand for various applications. The metal-polymer substrate interaction and the morphological structure at the interface influence the final properties of the composites of thin metal-polymer substrates. Thus, modifying the properties of the polymer substrate by wet (acid, alkali), dry (plasma), and radiation treatments (ultraviolet radiation and laser) appears as a significant step for increasing adhesion of thin film onto polymeric substrates. 

S. lost. Plasma polymerized organosiUcon thin films on reflective coatings, in Proceedings of the 33rd Annual Technical Conference, Society of Vacuum Coaters, 1990, p. 344. 

The hydrodynamic factors that influence the plasma polymerization process pose a complicated problem and are of importance in the application of plasma for thin film coatings. When two reaction chambers with different shapes or sizes are used and when plasma polymerization of the same monomer is operated under the same operational conditions of RF power, monomer flow rate, pressure in the reaction chamber etc., the two plasma polymers formed in the two reaction chambers are never identical because of the differences in the hydrodynamic factors. In this sense, plasma polymerization is a reactor-dependent process. Yasuda and Hirotsu [22] systematically investigated the effects of hydrodynamic factors on the plasma polymerization process. They studied the effect of the monomer flow pattern on the polymer deposition rate in a tubular reactor. The polymer deposition rate is a function of the location in the chamber. The distribution of the polymer deposition rate is mainly determined by the distance from the plasma zone and the... 

Plasma polymerizations are also very common 30,35-38) jt js possible to convert almost every organic compound into a polymer by using vigorous reaction conditions 35,39) Even under mild conditions various olefines or dienes polymerize readily, either in the gaseous phase or on the surrounding walls. This makes it possible to coat various objects with thin polymer films, a technique which can be used to modify surfaces. 

The XPS information indicated that the HFE plasma polymerization process deposited a film of roughly 2 nm on the TMS coating, which is itself about 50 nm thick. The plasma polymerization process using HFE to form the thin surface... 

The use of thin films derived from chlorotri-fluoroethylene as optical device protective coatings has been reported (100,101). Not only do the films protect the moisture sensitive substrates from atmos-phereic humidity but they also exhibited antireflection properties. Reis, et. al. (102) and Hiratsuka, et. al. (103) explored the use of plasma polymerized ethane as protective coatings for laser windows. The absorption and antireflection characteristics of these coatings were reported. 

Lipid bilayer membranes tethered to plasma-polymerized films as hydrophilic supports were another concept introduced recently [28], The plasma polymerization of maleic anhydride (MAH-PP), e.g., has led to the synthesis of thin polymeric coatings that appear to be suitable to act as a reservoir for an aqueous phase and a cushion for lipid bilayers [29], A crucial requirement for the use of such polymers as water containing supports for lipid bilayer membranes is their adhesion to the substrate. In a previous study [30] covalent binding of MAH-PP films to gold supports was achieved by a self assembled alkylthiol adhesion layer. The previous work has shown that maleic anhydride, when polymerized at a low duty cycle, can behave as a polyelectrolyte. The thin polymer layers were found to have a very low electrical resistance (ca. lOOQcm2) after immersion and subsequent hydrolysis/swelling in aqueous buffer. 

In the grafting from approach, a surface, that was previously activated e.g. by plasma treatment, is exposed to a monomer solution (Huang et al. 2003). A more simple, one-step procedure is to inadiate a polymeric surface like TCP, which is covered with the monomer solution, by an electron beam (Yamada et al. 1990). Alternatively, ultraviolet light and a photosensitiser can be utilised to initiate polymerisation and cross-linking (Curti et al. 2005). A completely different route to prepare thin SRP coatings with good adhesion to solid substrates is plasma polymerisation (Biederman and Osada 1992). In this case, NIPAAm is used as a precursor in a plasmachemical thin film deposition process (Cheng et al. 2005 Pan et al. 2001). 

Films fabricated with the plasma polymerization technique have various advantageous characteristics, such as a flawless thin coating, good adhesion to the substrate, mechanical toughness, and thermal stability, and therefore they have a wide variety of potential applications. 

Table 5 EIS Parameters Versus Corrosion Performance of Cold-rolled Steel Coated with a Thin Film of Plasma-Polymerized Trimethylsilane... 

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