A non-volatile resistive memory effect in 2,2 ',6,6 '-tetraphenyl-dipyranylidene thin films as observed in field-effect transistors and by conductive atomic force microscopy

The charge transport properties of 2,2',6,6'-tetraphenyldipyranylidene (DIPO-Ph4), a large planar quinoid pi-conjugated heterocycle, are investigated in field-effect transistor (FET) configuration and by conductive atomic force microscopy (c-AFM). The FET properties show a clear p-type behavior with a hole mobility up to 2 x 10(-2) cm(2) V-1 s(-1) and on/off ratio of 10(4). The transfer characteristics I-d/V-g present a clear hysteresis typical of a resistive memory effect. This memory effect is again observed by means of c-AFM in lateral mode using a nearby gold top-contact as the counter-electrode. The c-AFM current response recorded for variable distances d = 0.5-9.0 mm between the AFM tip and the top electrode shows a resistive switching behavior in the low-voltage 0.0-3.0 V region. Repeated "write-read-erase-read" cycles performed at low frequency reveal a non-volatile memory effect in the form of high-resistance and low-resistance states with a stable on/off ratio of 10(2) during cycling operation