Preparation of Polyimide Thin Films by Vapour Deposition and Solid State Reactions

In this chapter we describe the preparation of polyimide thin films by physical vapour deposition and comment on their potential application as a pure material or a thin layer matrix for producing nanocomposite layers. Their superb properties, such as a low dielectric constant, high thermaland photo-stability, high chemical resistance and high optical transmittance predetermine their widespread applications as a casts and layers used as insulators, protective or capsulation layers, mechanical or diffusion barriers, in optoand microelectronics. The bulk properties of the polyimide allowed the preparation of nanocomposite materials with organic chromophores as a “guest” (the embedded in the matrix nanosized particles). Moreover, some of the “guest” could bind to the polyimide chain. There are numbers of aromatic polyimides which are broadly used as thin layers in nanotechnology. Vapour deposition of the precursors and solid state reactions of imidization are of a greater priority than the spin coating and dipping methods. These as-deposited films by the vacuum deposition process consist of a dianhydride and diamine mixture, which by solid state reactions is converted to polyimide by thermal treatments or by combined microwave and thermal treatments. The physical vapour deposition as a “dry” method provides high purity for producing thin polymer films of controlled thickness, ratio of precursors and composition control of the so prepared layers. In this chapter we suggest possibilities for the practical application of vapour deposition of precursors and the following solid state reactions. By the used spectral methodFourier Transform Infrared Spectroscopy for analysis of the investigated kinetics of imidization reactions and microstructure of the layers are studied. The relationship between vapour deposition conditions and the presence of regular chains leading to the appearance of infrared bands is discussed. Polymers are also capable of forming a range of conformations depending on the backbone structure. The conditions for preparation by physical vapour deposition and solid state reaction of polyimide or nanocomposite polyimide layers are discussed.