Effects of film thickness and Ar/O₂ ratio on resistive switching characteristics of HfO_x-based resistive-switching random access memories

Cu/HfO_x/n⁺ Si devices are fabricated to investigate the influence of technological parameters including film thickness and Ar/O₂ ratio on the resistive switching (RS) characteristics of HfO_x films, in terms of switch ratio, endurance properties, retention time and multilevel storage. It is revealed that the RS characteristics show strong dependence on technological parameters mainly by altering the defects (oxygen vacancies) in the film. The sample with thickness of 20 nm and Ar/O₂ ratio of 12:3 exhibits the best RS behavior with the potential of multilevel storage. The conduction mechanism of all the films is interpreted based on the filamentary model.