Large conductivity changes in ion beam irradiated organic thin films

Using 2‐MeV Ar⁺ ion beam irradiation, we have generated conducting patterns in otherwise high resistivity, organic thin films of 3,4,9,10‐perylenetetracarboxylic dianhydride (PTCDA), 1,4,5,8‐napthalenetetracarboxylic dianhydride (NTCDA), and Ni phthalocyanine (NiPc). The room‐temperature resistivity of the films changes by 14 orders of magnitude from its as‐deposited value of ρ≳10¹⁰ Ω cm to ρ≅5×10⁻⁴ Ω cm at ion doses of 10¹⁷ cm⁻². The temperature (T) dependence of the resistivity follows ρ(T)∝exp[+(T₀/T)^1/2] over a wide range of dose and temperature. The characteristic temperature T₀ is found to be a function of dose. The exp(T₀/T)^1/2 behavior of ρ(T) is consistent with charge transport due to hopping between isolated, conducting islands.