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

Abstract

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 thermal-and photo-stability, high chemical resistance and high optical transmittance predetermine their wide-spread applications as a casts and layers used as insulators, protective or capsulation layers, mechanical or diffusion barriers, in opto-and 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 method-Fourier 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.

Analysis of Charge Relaxation in the Modified Films of the polyimide

“…Teflon Polyimide Teflon It is known [3] that an exchange of charges between the ions that come from the gas discharge and a polymer film surface according to the mechanism of Auger neutralization occurs in the process of charging. As a result, the electret homo-charge appears.…”

Chemical and Physical Properties of Polyimides: Biomedical and Engineering Applications

“…These processes are to great extent accelerated and controlled in the thermal treatment of the condensed solid phase which represents PAA, with regard to their transformation to PI by means of reaction of polycyclodehydration in solid state to linear PI [7,10,11]. The FTIR spectra of individual films of PMDA, ODA and PAA are shown in figure 2.…”

“…Our studies have focused primarily on vapour deposition of precursors and solid state imidization reaction [7,10,11,12]. Vapour deposition processes of organic layers play an important role in polytronics.…”

“…All these additional processes generate enough number of active particles as free radicals and ions in the gas phase. The disadvantage of these so-called vapour assistance deposition processes is the need for very precise control [7,13].…”

“…The second step is nucleophillic ring closure due to dehydration and imide ring formation. One of the disadvantages of this method is unavoidable presence of solvents and need for their removal [7]. During the polycyclodehidration side reaction is run that defy stereoregular control [1].…”