Effect of Current Compliance on Resistive Switching Characteristics of Amorphous Ternary Rare Earth Oxide SmGdO3 Thin Films Grown by Pulsed Laser Deposition

Recently the electric-field controlled resistive switching phenomenon in metal oxides has drawn tremendous attention for the development of next generation low power, high speed, high density and nonvolatile resistive random access memory (RRAM) devices. The memory effect in RRAM devices is realized through switching of the resistance of the device between the two states (high and low) of resistances. Depending on the polarity of the applied bias voltages, the resistance switching (RS) characteristic can be classified into two types namely unipolar and  bipolar. Among these, the unipolar resistance switching is more preferred due to large contrast in low and high resistance ratio. We have studied RS behavior in new amorphous high-k dielectric ternary rare earth oxide SmGdO₃ (SGO) with high and linear dielectric constant of ~ 19. We observed multilevel resistance switching in Pt/SGO/Pt ReRAM device simply by controlling the compliance current during the transition from high to low resistance state. The 4-levels of resistance states with sufficient ratio of neighboring low and high resistances were observed, which is expected to enhance the data storage capability of ReRAM device by storing more data in a finite space. It was observed that the higher the I_CC imposed on the device, the lower resistance value obtained in LRS. Under different I_CC values between 1 to 5mA, we observed different distinguishable values of lthree ow resistance states and one high resistance state. Temperature dependent studies of the resistances in three low and one high resistances were carried out to understand the mechanism of RS which indicated that resistive switching could be explained by the formation/rupture of conductive filaments formed out of oxygen vacancies and metallic Gd atom. X-ray Photo electron spectroscopy of these samples supported this observations. Based on our experiments the observed multilevel conduction in the device was explained by the variation in the size and or density of conducting filament. Current conduction mechanisms in all the resistance states were also studied. The observed reproducible and nonvolatile multilevel resistive switching, good contrast between them and their good retention and endurance characteristics indicates that SGO may be a promising material for the future nonvolatile multi-bit ReRAM devices. Further studies are currently underway.