Silver particulate films on softened polymer substrates pre-coated with selenium

The formation of subsurface particulate films when certain inorganic materials are vacuum deposited on softened polymer substrates is known for long. The subsurface structure formation is dependent on thermodynamic as well as deposition conditions. The subsurface particulate structure is similar to the discontinuous films under the polymer cover. The discontinuous films do exhibit certain interesting properties and the exploitation of these properties is constrained by the instabilities in their properties in vacuum as well as the degradation in atmosphere. The subsurface particulate structures are believed to be a solution against the instabilities of discontinuous films. Further, the morphology of the subsurface particulate structures is strongly dependent on the nature of the polymer and the polymer metal interaction. While interacting polymers like poly(2-vinylpyridine) (P2VP) and poly(4-vinylpyridine) (P4VP) suffer from the hygroscopic nature, inert polymers like polystyrene (PS) do not facilitate organised structure with small particles and small separations. The modifications of an inert polymer like PS by blending with an interacting polymer like P4VP, by electron beam irradiation to create free radicals, by doping with surfactants like 3-mercaptopropyltrimethoxysilane (MPTMS), by creating pre-nucleation centres with selenium have been carried out. The silver particulate films on such modified softened polystyrene substrates show interesting optical, structural and electrical properties. Some of these results are discussed in the article.