On the Existence of Two Different Resistive Switching Mechanisms in Metal Organic Charge Transfer Complex Thin Films

In this study we will describe the switching effect in the metal-organic charge transfer complex system Cu:7,7,8,8- Tetracyanoquinodimethane (TCNQ). The samples were prepared by physical vapor deposition (PVD). This process results in the formation of amorphous Cu:TCNQ thin films with a ratio of 1:1 of the metal and the organic compound. Simple capacitor like test structures were prepared with Cu:TCNQ thin films as an active layer. These devices showed reproducible resistive switching. The origin of the bistable switching in Cu:TCNQ thin films is discussed. In this study, we show the existence of two distinctive reversible resistive switching effects in Cu:TCNQ thin films. Three different states could be observed, a high resistance state (R_ON in the 10⁷ Omega range), a low resistance state (R_OFF in the 10¹ Omega range) and a very low resistance state with metallic like behavior (R_MET in the 10¹ Omega range). The switching to the very low resistance state requires a higher switching voltage and is much less stable than switching to the low resistance state. Therefore, the main focus is on the latter effect which has more potential for possible future applications.