TRANSPORT-PROPERTIES OF ION-IMPLANTED POLY(P-PHENYLENE VINYLENE)

We have studied the effect of ion implantation on transport properties (thermopower S, dc conductivity sigma, ac conductivity sigma(T)) of p oly (p-phenylene vinylene). We have noticed that the thermopower sign is characteristic of the implanted ion (S > 0 for halogen, S < 0 for a lkali) at low implantation energy (E less-than-or-equal-to 50 keV). Th e slope of sigma = f (T-1) varies, with values for activation energy b etween 32 meV (D = 10(16) ions/cm2) and 57 meV (D = 10(15) ionS/cm2) : the activation energy falls as the fluence increases in the case of i mplantation at low energy (E less-than-or-equal-to 50 keV). AC conduct ivity has been studied as a function of frequency nu (nu = 20 Hz - 1 M Hz) and of temperatures T (T = 100 K - 380 K). For lower fluences (D = 2.10(15) ionS/CM2), at low temperatures the ac conductivity shows hop ping behaviour, switching to activated behaviour at higher temperature s. For higher fluences (D = 2.10(16) ions/CM2) the main processes are thermally activated. Thus for a high implantation energy (E = 250 keV) , the related conductivity is less thermally activated and the curve s igma(T) = r (1/T) slightly depends on temperature (hopping mechanism).