Resistive switching and noise in non-volatile organic memories

The authors found quant. criteria to characterize the states of the device: (1) pristine devices show at low bias I proportional to Vm with m = 0 pointing to trap filling and at higher bias m = 6 pointing to tunneling. The 1/f noise is characterized by 10-7 <.alpha..mu. (cm2/Vs) <10-5; (2) forming state is a transition between pristine and switched-state. The time dependent soft breakdown in the Al-oxide goes hand in hand with strong discrete multi level resistive switching (RTS) with a 1/f 3/2 spectrum. Once the device is switched in the high (H-) or low (L-) conductance state it never comes back to the pristine state. (3) The H- or L-state is characterized by I proportional to Vm with either m = 1 or m = 3/2. The injection model predicts the current level and the dependence of the 1/f noise on current. Reliable switched devices show mainly 1/f noise. In the L-state there is often a 1/f 3/2 contribution on top of the 1/f noise indicating multi level switching. Reliable switches between the L- and H-state are characterized by a resistance R that changes for example by a factor 30 and the relative 1/f noise, fSI/I2C1/f follows the proportionality: C1/f proportional to R with a .alpha..mu.-value of .apprx.3 10-2 cm2/Vs. The explanation from the noise for C1/f proportional to R is that the no. of carrier in the transport switches due a change of the no. of parallel conducting paths in the polymer. The onset of switching seems to be at spots of the Al / Al2O3 / polymer interface