LOW-FREQUENCY NOISE TO CHARACTERIZE RESISTIVE SWITCHING OF METAL OXIDE ON POLYMER MEMORIES

Resistive switching in aluminum-polymer diodes has been investigated by noise measurements. Quantitative criteria to characterize the diode states are: (i) Pristine state shows I proportional to V-m with m approximate to 6 at higher bias typical for tunneling. The resistance is very high, 1/f noise is very low, but the relative 1/f noise, fS(I)/I-2 equivalent to C-1/f is very high. (ii) Forming state is a time-dependent soft breakdown in the Al-oxide that results in random telegraph signal noise (RTS) with a Lorentzian spectrum or in multi-level resistive switching (MLS) with a 1/f(3/2) or 1/f-like spectrum. (iii) The H- or L-state shows I proportional to V-m with m = 1 for V < 1V and 3/2 < m < 2 for V > 1V. Deviations from ohmic behavior are explained by space charge limited current in the polymer. Reliable H-and L-states show pure 1/f noise, a resistance R that changes by at least a factor 30 and 1/f noise that follows the proportionality: C-1/f proportional to R with a proportionality factor alpha mu(cm(2)/V-S) of the same level as observed in metals, polymers and other semiconductors. C-1/f proportional to R is explained by switching of the number of homogeneous conducting paths in parallel. Deviations in C-1/f proportional to R are also explained. In the pristine state and even in the H-state, only a fraction of the device are is carrying current and switching seems to be at spots of the Al/Al2O3/polymer interface.