Memory effects in a submicrometre metal-dielectric composite system

Electrically driven switching of resistance states is observed in a system prepared by depositing Co and Cu layers in trenches of widths 50-500 nm in SiO2, followed by application of a controlled high-density current. This 'forming' process leads to both an increase of resistance and a transition from metallic conduction to activated tunnelling. In the resulting system, the value of resistance can be switched reversibly by positive or negative voltage. After applying a positive bias > 1.3 V the low-bias resistance decreases, while after applying a negative bias of the same value it increases. The resistance ratio between the high-resistance and low-resistance states of the system is in the range similar to1.5-6. A possible interpretation of the observed phenomena is discussed.