Physical and electrical properties of band-engineered SiO2/(TiO2)x(SiO2)1−x stacks for nonvolatile memory applications

In our study, the physical properties of (TiO 2 ) x (SiO 2 ) 1− x , including band-gap, band-offset, and thermal stability and the electrical properties of band-engineered SiO 2 /(TiO 2 ) x (SiO 2 ) 1− x tunnel barrier stacks, including the tunneling current and charge-trapping characteristics for applications to nonvolatile memory devices were investigated. It was observed that the band-gap and band-offset of (TiO 2 ) x (SiO 2 ) 1− x can be controlled by adjustment in the composition of the (TiO 2 ) x (SiO 2 ) 1− x films. Ti-silicate film with TiO 2 :SiO 2 cycle ratio of 1:5 was maintained in an amorphous phase, even after annealing at 950 °C. The tunneling current of the band-engineered SiO 2 /(TiO 2 ) x (SiO 2 ) 1− x stacked tunnel barrier was larger than that of a single SiO 2 barrier under a higher external bias, while the tunneling current of a SiO 2 /(TiO 2 ) x (SiO 2 ) 1− x stacked tunnel barrier under a lower external bias was smaller. Charge-trapping tests showed that the voltage shift for SiO 2 /(TiO 2 ) x (SiO 2 ) 1− x is slightly larger than that for single SiO 2 .