A metal/Ba0.6Sr0.4TiO3/SiO2/Si single film device for charge trapping memory towards a large memory window

Abstract

In this study, we present a metal/Ba0.6Sr0.4TiO3/SiO2/Si (MBOS) structure for charge trapping memory, where the single Ba0.6Sr0.4TiO3 film acts as the blocking layer and charge trapping layer. This MBOS device structure demonstrates excellent charge trapping characteristics, a large memory window up to 8.4 V under an applied voltage of ±12 V, robust charge retention of only 4% charge loss after 1.08 × 104 s, fast switching rate, and great program/erase endurance. These attractive features are attributed to the high density of defect states in the Ba0.6Sr0.4TiO3 film and its inter-diffusion interface with SiO2. The properties of defect states in the Ba0.6Sr0.4TiO3 film are investigated through measurements of photoluminescence and photoluminescence excitation spectroscopy. The energy levels of these defect states are found to be distributed between 2.66 eV and 4.05 eV above the valence band. The inter-diffusion at the Ba0.6Sr0.4TiO3/SiO2 interface is observed by high-resolution transmission electron microscopy. More defect sites were created to obtain a better charge trapping capability and retention characteristics.