Demonstration of high-performance STO-based WORM devices controlled by oxygen-vacancies and metal filament growth

Abstract

Herein, we propose high-performance Ti/STO/n⁺-Si and Ag/STO/n⁺-Si write-once-read-many-times devices, where the resistance transition mechanisms are controlled by oxygen vacancies in the STO layer and metal atoms from the electrochemically active Ag electrode, respectively. The as-deposited STO films have a low oxygen-vacancy content of 12.2%. When the Ti electrode is deposited, the formation of a thin TiO_x interfacial layer at the Ti/STO interface is achieved, which leads to an increase of oxygen vacancy content in the STO layer to 28.6%. The relatively higher oxygen vacancy density means that the Ti/STO/n⁺-Si device can provide a voltage-polarity-independent memory function. In contrast, the resistance transition of the Ag/STO/n⁺-Si device can be limited in the positive voltage region because Ag cations can only be driven into the STO layer using a positive bias. Both devices show high I_LRS/I_HRS ratios, superior data retention capability, and fast transition speeds.