Barium titanate write-once read-many times resistive memory with an ultra-high on/off current ratio of 108

Write-once read-many times (WORM) resistive memories fabricated using perovskite barium titanate (BaTiO3, BTO) resistive switching (RS) layer are demonstrated in this study. The BTO RS layers with thicknesses of 3.2-8.5nm are fabricated by radio frequency sputtering at room temperature. Annealing processes at 400-600 °C are used to modify the oxygen vacancy content in the BTO layer and thereby control the OFF-state current of an Al/BTO/n+-Si WORM device. The ION/IOFF ratio increases with increasing annealing temperature until 500 °C. A negative effect is observed when the temperature further rises to 600 °C. The optimal Al/BTO/n+-Si device shows an ultra-high ION/IOFF ratio of 108 and a low coefficient of variation of 6% for set voltages. The writing speed is 80ns and the power consumption is 400 pJ. In addition, retention and stress tests are performed to confirm high data storage reliability of the device. Mechanisms for voltage-polarity independent writing process and the related energy band diagrams are explored.