Resistive switching in Al2O3 based trilayer structure with varying parameters via experimentation and computation

Abstract

Resistive switching characteristics in Al (40 nm)/Al2O3 (x nm)/Ni (50 nm) were analyzed while the middle layer thickness is varied from 5 nm to 20 nm with an increment of 5 nm each. Al/Al2O3/Ni with a total thickness of 100 nm showed the most prominent results. The current compliance was 100 mA while the voltage range for each design varied in the range of ±4 V, showing bipolar resistive switching. The double logarithmic curves indicated the presence of the Ohmic conduction and space-charge limited current mechanism. Moreover, density functional theory based calculations were performed for aluminum oxide with induced oxygen vacancy defects. The structures with oxygen vacancies showed that the nature of aluminum oxide was converted to semi-conducting from insulating, i.e., the bandgap was decreased from ∼6 eV to ∼0.6 eV. Density of states displayed that the atoms neighboring the oxygen vacant sites are responsible for a shift in states toward the valence band and Fermi level. Formation of a conduction filament (CF) is found essential for conduction in resistive random access memory (RRAM), and the computational analysis clarified that induction of oxygen vacancies is vital for the formation of CF. Finally, this work presents a detailed discussion and understanding of resistive switching in aluminum oxide-based RRAM, which is significant in the advancement of non-volatile data storage application.