Conduction mechanism and impedance analysis of HfO[formula omitted]-based RRAM at different resistive states

Abstract

Conduction mechanism and impedance analysis of both the low resistance state (LRS) and high resistance state (HRS) are performed on TiN/HfOx/Pt resistive-switching memory devices at various temperatures. The dc conduction mechanism in LRS is dictated by Ohmic conduction, whereas by trap controlled space-charge-limited current conduction in HRS. The XPS analysis results on the surface of the HfOx film indicated the presence of oxygen deficiencies. The equivalent physical model under various resistance states is established by using ac impedance spectroscopy method, that is related to oxygen vacancies in the HfOx film. We further discussed the activation energy of dc and ac in the HRS and found the conduction occurs at the grain boundary. Through analysis of different resistance states of HfOx-based resistive switching memories, the conduction mechanism correlation between time and frequency domain is established.