Study of Ti/TiO2/Ti selector for the memristive crossbar array

Abstract

Selectors are non-linear elements used in memristor circuits. We explore a Ti/TiO2/Ti selector as part of a one-selector–one-resistor memristor for high-density crossbar arrays. The Ti/TiO2/Ti stack is fabricated using magnetron sputtering and e-gun thermal evaporation. Selectors fabricated via magnetron sputtering consistently exhibit non-linear behavior, with a non-linearity coefficient reaching 6.2 at a low operating voltage (0.5 V), stable performance at high current, and a fabrication compatible with the standard silicon technology. The observed non-linearity can be explained by the combination of electron trapping/detrapping with an excitation energy of ∼0.3 eV. In contrast, selectors fabricated using e-gun thermal evaporation have history-dependent voltage-controlled negative differential resistance. Later, their behavior evolves into a non-linear rectifying I–V curve. This phenomenon can be attributed to the evolution of the oxygen vacancies in TiO2.