THERMOSTIMULATED SWITCHING IN THIN POLYMER-FILMS

The paper presents results of a study on a new kind of instability observed in thin poly(3,3'-phthalidylidene-4,4'-biphenylylene) films, namely, thermostimulated switching. This occurs at 265 K as a result of heating at a certain rate. After switching the sample transits to a metallic state. Investigations of the polymer dielectric loss and IR spectrum under similar heating regimes show the existence of relaxation excitations at this temperature. Another range of excitations is detected at 190 K. According to IR spectra, in the low temperature range, excitation of nonvalence aromatic distortion oscillations of the C-H bonds take place, whereas C=C double bonds are excited in the high temperature range. Dependence of the intensity of excitations on film thickness and heating regime allows us to suggest that they are associated with the thermostimulated ionization of trapping states. The model of polaron lattice formation is discussed as a possible explanation of the observed dielectric-metal transition.