PERCOLATIVE METAL-INSULATOR-TRANSITION IN EXCIMER-LASER IRRADIATED POLYIMIDE

The metal-insulator transition observed in excimer laser irradiated po lyimide is presented as a new experimental method to study three-dimen sional percolation. The conductivity critical exponent t and the perco lation threshold Phi(c) are measured in situ for the transition under both Ohmic and non-Ohmic conditions. The experimental values obtained in the Ohmic case were Phi(c) = 0.31 +/- 0.06 and t = 2.00 +/- 0.05. T hese values are in close agreement with theory. The dependence of the critical exponent on current voltage characteristics of conducting sit es is demonstrated for the first time.