ELECTRICAL-CONDUCTION MECHANISMS IN ELECTROCHEMICALLY FORMED AMORPHOUS FILMS OF NB2O5

Electrical conduction in amorphous Nb2O5 oxide films, obtained by electrochemical methods, has been measured in the temperature range 293 to 420 K. Different conduction processes are considered, depending on the applied electric field. At low fields, the results are consistent with a Small Polaron Hopping process in the high-temperature range, while Variable Range Hopping is suggested at room temperature. When the electric field is higher than congruent-to 5 x 10(6) V m-1, the field enhanced emission of carriers from a discrete trap level is in accordance with the 'usual' Poole-Frenkel model. A space-charge-limited process is observed only at low temperatures at intermediate values of the applied field. Deviation from the Poole-Frenkel effect are observed at fields higher than 5 x 10(7) V m-1. Current-controlled negative resistance is, then, associated with irreversible switching.