Modification of electrical properties of tungsten oxide nanorods using conductive atomic force microscopy

Electrical conduction of tungsten oxide nanorods has been characterized by conductive atomic force microscopy (C-AFM). The conduction measurements were carried out in air using a conductive P⁺-type diamond-coated tip. This technique allows either the simultaneous measuring of the topography and the special current distribution or the recording of the current voltage distribution in a single point mode. We have proposed an equivalent electrical circuit which allows us to understand the I(V) curves. During C-AFM observations we have observed significant changes in image contrast and hysteresis in the I(V) characteristics which depend on the applied bias voltage. The bias dependence effect is interpreted as being due to a local oxidation-reduction phenomenon induced by the tip in the presence of water.