Resistive switching properties of hafnium oxide thin-films sputtered at different oxygen partial pressures

We report a study on the effects of O₂/Ar ratio on the resistive switching properties of HfO_x thin-films deposited by using RF magnetron sputtering. Ar is kept at a constant flow rate of 30 SCCM and O₂ is varied from 0 to 30 SCCM during the deposition of these thin films. The UV–Vis spectra reveled that the transmission percentage of these films increase proportionally with increase of O₂/Ar ratio up to a critical value. Further, the peak positions at 2.7 and 2.9 eV in PL spectra were attributed to singly and doubly charged oxygen vacancies respectively. These defects and vacancies alter the switching behavior of the devices. Moreover, the XPS data showed that the intensity of O–O bond peak decreases as O₂/Ar ratio increases. Therefore, the switching performance shows a significant influence of the amount of inletting the oxygen gas with Ar during the deposition, thereby an improvement in the resistance ratio (R_off/R_on) of these HfO_x based devices is noticed.