Layer dependent direct tunneling behaviors through two dimensional titania nanosheets

Abstract

Two dimensional titania nanosheets are drawing increasing attention in academic and industrial community because of their versatile properties. The elucidation of the electron tunneling effect through their intrinsic metal-oxide-metal (MOM) atomic structures is imperative to further advance their applications as atomic dielectrics and memristors. The direct tunneling behaviors through Ti1-δO24δ- nanosheets sandwiched by two metal electrodes are studied by a modified WKB approximation and conformed by ab-initio calculation. Our results show that the tunneling current density depends exponentially on the stack number of dielectric Ti1-δO24δ- layers, decreases by 3–4 orders of magnitude for each layer addition, varying from 106 to 10−8 A/cm2 in one- to five-layer MOM structures. Also, it is highlighted that the localized intercalation charges naturally embedded in chemically-derived Ti1-δO24δ- nanosheets could reduce tunneling current by 3 orders of magnitude and that a thickness threshold of three layers (∼2 nm) exists as to the titania nanosheets not to exceed a gate current density of 1 A/cm2 at 1 V. The present method could be extended to better clarify the electron tunneling behaviors in other two-dimensional gate dielectrics.