Plasma polymer-metal films

Preparation of plasma polymer/metal films in low temperature nonequilibrium plasmas is generally based on a combination of two processes applied simultaneously ... 

As such exemplary experimental material, plasma polymer thin films with embedded silver particles are selected [3]. These films were made by simultaneous or alternating plasma polymerization and metal evaporation. The films can be deposited as multilayers consisting of two polymer thin films and a nanoparticle-containing film between these films. Because of the two plasma polymer layers on either side, the particles are completely embedded in a homogeneous media. The multilayer systems are very appropriate for determining particle size and investigating the interface between metal particles and plasma polymer matrix, because here metal nanoparticles are embedded in one plane. This allows a simple determination of the particle size and shape in the TEM. 

H. Biederman, L. Martinu, Plasma polymer-metal composite films, in R. d Agostino (Ed.), Plasma Deposition, Treatment and Etching of Polymers, Academic Press,... 

Avseenko et al. (2001) immobilized antigens onto aluminum-coated Mylar films by electrospray (ES) deposition. Various surface modifications of the metallized films were studied to determine their abilities to enhance sensitivity. The plastic surfaces were firsf cleaned by plasma discharge treatment, followed by coating with proteins (BSA and casein) or polymers such as poly (methyl methacrylate) or oxidized dextran, or they were exposed to dichlorodimethyl silane to create hydrophobic surfaces. Protein antigen was prepared in 10-fold excess sucrose and sprayed onto the surfaces to form arrays with spot diameters between 7 and 15 pm containing 1 to 4 pg protein. 

The rapid development of solid state physics and technology during the last fifteen years has resulted in intensive studies of the application of plasma to thin film preparation and crystal growth The subjects included the use of the well known sputtering technique, chemical vapour deposition ( CVD ) of the solid in the plasma, as well as the direct oxidation and nitridation of solid surfaces by the plasma. The latter process, called plasma anodization 10, has found application in the preparation of thin oxide films of metals and semiconductors. One interesting use of this technique is the fabrication of complementary MOS devices11. Thin films of oxides, nitrides and organic polymers can also be prepared by plasma CVD. 

Friedrich JF, Retzko I, Kuhn G, Unger W, Lippitz A (2001) Metal doped plasma polymer films. In Mittal KL (ed) Metallized Plastics, vol 7. VSP, Utrecht p 117-142... 

Polymer substrates are often coated with metals for a wide variety of reasons. In many cases, the chemical condition of the surface has been found Q) to alter the adhesion of the metal film to the substrate. In particular, oxygen plasma treatment of polymer surfaces before metal deposition has been found (, 4)... 

When a very thin film (e.g., thicknesses of less than 1 pm) of a polymer is applied to a smooth surface of platinum, most polymers peel off within minutes upon immersion in liquid Lf20. This is also true for most plasma polymers applied to platinum surfaces. However, when an ultrathin film of CH4 LCVD was deposited under the conditions that provide plasma energy density sufficiently high to sputter aluminum from the electrodes, tenacious adhesion that survived over 10 h of boiling in saline solution was obtained, probably due to the incorporation of electrode metal at the interface. 

In certain applications of plasma polymerization, the incorporation of electrode material, particularly in a controlled and designed manner, is extremely useful and becomes a great asset in LCVD. For instance, a thin layer of plasma polymer of methane with a tailored gradient of copper has been shown to improve the adhesion of the thin layer to a copper substrate as well as the adhesion of metal to a polymer film [3,4]. In general applications of LCVD, in which the metal contamination should be avoided, it is important to select the electrode material that has low sputtering yield. Titanium has been used successfully in such cases. 

Figure 21.3 Effect of normalized energy input, WjFM, of the methane glow discharge on the sputter deposited metal content in the plasma polymer of methane film.

The results of tensile lap-shear and chemical composition tests for different process schemes are shown in Tables 21.2-21.4. Metal analyses of the initial plasma coating layer and those of the failed surfaces after tensile lap-shear tests confirm that the failure occurred at the interface between the substrate surface and the bottom of the plasma polymer film. These results show that the intermediate layer provided by grading of the metal content throughout the plasma polymer film can improve the strength between the polymer and metal films. The graded metal-containing plasma polymer film can join a polymer and a metal with strong adhesion, and also reduce... 

Figure 21.9 The proposed seetional model of a eomposition-graded transitional buffering film layered by double-graded proeess A, pure methane plasma polymer layer B, composition-graded layer of methane plasma polymer and metal C, sputtered metal layer with earbon contamination.

Composition-graded composite films of plasma polymer and metal can be controlled to give surfaces capable of being electroplated. 

Surface conditioning by plasma pretreatment with oxygen and hydrogen is a crucial factor in obtaining very strong bonding at the interface between the substrate and composite plasma polymer film as a preplate for metallization. 

The shear strength of coatings metallized by employing composition-graded films is dependent on the extent and strength of chemical bonding between the substrate surface and the plasma polymer film. 

Parylene N to smooth surface materials has been reported with the application of plasma depositions [13,14]. It was reported that excellent adhesion of Parylene C coating to a cold-rolled steel surface was achieved using plasma polymer coatings, in turn giving rise to corrosion protection of the metal [15]. Another major deficiency of Parylene C is its poor painting properties when paint is applied on a Parylene C film, due to its extremely hydrophobic surface. Because of this, surface modification of Parylene films is necessary to enhance their adhesion performance with spray primers. 

It is clear from the study on pure iron that oxides participate in LCVD of TMS, and characteristics of plasma polymer films differ depending on the extent of oxides present on the surface when LCVD is applied. Oxides on the surface of pure iron are more stable than those on steel and hence more difficult to remove, but this can be effected by plasma pretreatment with (Ar + H2) mixture. SAIL by LCVD involving removal of oxides provides excellent corrosion protection of pure iron. The key factor of SAIL by LCVD for corrosion protection of metals in general is the handling of oxides, which depends on the characteristic nature of the metal oxide to be handled. Once strong chemical bonds were formed between nanofilm of plasma polymer, either through oxides or direct bonding to the substrate metal, the LCVD film acts as the barrier to corrosive species. 

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