Electron beam lithography of two-component radical ion salt films: reversible charge transfer in copper- and silver-TCNQ

Summary form only given. Charge transport in thin conducting organic films is attracting increasing attention because of low-dimensional electron- and spin motion. We investigate the electron beam induced lithography process in radical ion salts using copper and silver tetracyanoquinodimethane (Cu(TCNQ)/sub x/ and Ag(TCNQ)/sub x/) with x=1 and 2, respectively. The films have been prepared in a vacuum, chamber attached directly to a modified scanning electron microscope. The metal and TCNQ were evaporated in separate layers of thicknesses corresponding to the desired stoichiometry. The salt films were obtained by a solid state reaction which was carried out during annealing the multilayer samples. The substrate temperature during film deposition and during the lithography process was varied between 70 K and 350 K. Electrical measurements were performed in situ. Absorption spectroscopy of large irradiated areas proves the back-transformation of the salt into neutral TCNQ using electron energies of 2-10 keV and beam currents of 1-10 nA with typical irradiation times of 0.1 ms per pixel. This effect is used to prepare submicron thin areas of lower conductivity in the semiconducting salt film. The application of these microstructures in the field of molecular electronics is dicussed with respect to electrical and optical switching properties of these films.