Electrical properties of ZrO ₂ and YSZ films deposited by pulsed laser deposition

Polycrystalline ZrO ₂ and yttria-stabilized ZrO ₂ thin films have been deposited on Pt/Ti/SiO ₂/Si substrates by pulsed-laser-deposition methods. Pt/ZrO ₂/Pt and Pt/YSZ/Pt capacitor structures show giant conductivity switching behaviors which can be utilized for nonvolatile memory devices, Maximum on/off ratio of 10 ⁶ and good endurance even after 10 ⁵ times conductivity switching are observed in a typical Pt/ZrO ₂/Pt whose ZrO ₂ film has been deposited at 100°C and at an oxygen pressure of 50 mTorr. The Pt/ZrO ₂/Pt structure exhibits two ohmic behaviors in the low-voltage region (V < 1.4 V), depending on the value of previously applied high voltage, and Schottky-type conduction in the high-voltage region (1.4 V < V < 8,9 V), It seems that conductivity switching behaviors in our Pt/ZrO ₂/Pt structure result from changes in both the Schottky barrier and the bulk conductivity controlled by applied voltages. A Pt/YSZ/Pt capacitor structure has more stable reset voltage and current state than a Pt/ZrO ₂/Pt capacitor structure. Moreover, a Pt/YSZ/Pt capacitor structure shows higher conductivity than a Pt/ZrO ₂/Pt capacitor structure, which may result from substitution of Y ³⁺ ions for Zr ⁴⁺ ions.