a1 Department of Electrical Engineering, Stanford University, 420 Via Palou Mall, Stanford, CA 94305, U.S.A.
a2 Department of Material Science and Engineering, Stanford University, 420 Via Palou Mall, Stanford, CA 94305, U.S.A.
The interactions and ordering of oxygen vacancies in rutile TiO2 were thoroughly investigated by density functional calculations to search for atomic configurations of the conductive filament. As random isolated vacancies could not support the low-resistance state conduction in TiO2 ReRAM, vacancy ordering was introduced in  and  directions of the lattice to study the electronic structures. The calculation results revealed that a di-vacancy chain in  direction makes the electrons delocalized in that direction, which is identified as a possible configuration of the conductive filament. This low-resistance state can be effectively disrupted by moving oxygen vacancies out of the filament to reach high-resistance states.