A soliton model of the non metal-metal transition in implanted organic (CH)_x and inorganic (LiF) materials

Abstract

We describe two cases of non metal-metal transitions induced by ion implantation: one in lithium fluoride and the other in polyacetylene which have respectively a three-dimensional and one-dimensional structure. We recall the model of percolation proposed in a previous paper³ for LiF and show that a metallic behaviour is induced in (CH)_x by implantation of active impurities, such as C1⁻ and I⁻. The conductivity is increased by more than 5 orders of magnitude with 5·10l6 I/cm² showing that the doping effect remains larger than the degradation due to radiation damage. We show that in the two systems the impurities act like complexes of charge transfer and that a soliton model could be used in LiF to describe the precursor state of the percolation transition.