Electrical conduction mechanisms in electrochemically formed amorphous films of Nb₂O₅

Abstract

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 ⋍ 5×10⁶Vm⁻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 5×10⁷Vm⁻¹. Current-controlled negative resistance is, then, associated with irreversible switching.