Effects of O$_{\bf 2}$/Ar Ratio and Growth Temperature on Resistive Switching Characteristics of Al/HfO$_{\bm x}$ /ITO Memory Devices

O
₂
/Ar ratio and growth temperature during the deposition process of HfO
_x
thin film have the significant effect on the OFF-state current of Al/HfO
_x
/ITO devices. In order to enhance the quality of HfO
_x
layer, HfO
_x
thin film was sputtered at 300-700 K in a mixed ambient of Ar and oxygen. For HfO
_x
thin films deposited at 500 K with O
₂
/Ar ratio of 0.2, the resistive switching ratio is enhanced by five orders of magnitude. The resistive switching I-V characteristics at 120-300 K were investigated. Using temperature-dependent transport in HfO
_x
thin film, two transport mechanisms cocontribute to the high resistance state current: the correlated barrier hopping conduction and the weak metallic filamentary conduction.