Metal/ZnO/MgO/Si/Metal Write-Once-Read-Many-Times Memory

Write-once-read-many-times memory (WORM) devices were fabricated using ZnO and ZnO/MgO as active layers on Si. Devices fabricated with ZnO show a different memory effect at different current compliances such as WORM at 100 μA, 500 μA, and 1 mA, resistive switching (RS) instead of WORM at 5 and 10 mA, and WORM and RS coexisting at 20, 50, and 100 mA, while devices fabricated with ZnO/MgO show WORM only at all current compliances. A few nanometers of MgO layer play a major role in preventing devices from reset at all current compliances because the much lower drift velocity of oxygen vacancy in MgO and accumulation of negatively charged O 2- ions at the interface between ZnO and MgO prevent the conducting filaments composed of oxygen vacancies from breaking.