Unipolar resistive switching behavior has been investigated in Pt/Co3O4/Pt stacks. The resistance ratio of the high- and low- resistance states is over 5 x 10(3). The "ON/OFF" operation of the memory cells can be repeated more than 200 times at room temperature. The resistance of the two states can be kept for more than 16 h without showing degradation. The temperature dependence of the resistance shows a metallic behavior at the low-resistance state, but a semiconductor-behavior at the high-resistance state. The mechanism responsible for the observed unipolar resistive switching behavior has been discussed. (C) 2010 Elsevier B.V. All rights reserved.