Non-equilibrium character of resistive switching and negative differential resistance in Ga-doped Cr2O3 system

We have synthesized Ga-doped Cr2O3 system with compositions Cr1.45Ga0.55O3 and Cr1.17Ga0.83O3 by chemical co-precipitation route and post annealing at 800^C. The samples have been stabilized in rhombohedral crystal structure with space group R3C. The present work focuses on the study of non-linear current-voltage (I-V) characteristics of the samples, which exhibited many interesting electronic properties, e.g., I-V loop, resistive switching, bi-stable electronic states, and negative differential resistance. The non-equilibrium character of the I-V characteristics has been studied by measurement of bias voltage cycling up to 20 times and current relaxation with time at set bias voltage. The charge conduction process in the samples has been understood by analysing I-V curves using different phenomenological models based on electrode-limited and bulk-limited charge conduction mechanisms proposed for metal electrode-metal oxide-metal electrode (M-MO-M) junctions. It is understood that competitions between injection of charge carriers from metal electrode to metal oxide, charge flow through the material (trapping/de-trapping and recombination of charge carriers at the defect sites), space charge formation at the junctions of electrodes and metal oxides, and ejection of electrons from metal oxide to metal electrode control the non-equilibrium I-V characteristics in the present samples.