Sub-Thermionic Topological Gate Dielectrics with Metallic Surface States Preserved beneath PhaseTransitioned Topological Insulators

Abstract

As silicon approaches its physical limitation in the sub-1.5 nm node, two-dimensional (2D) materials are emerging as promising candidate materials for future nanoelectronics due to their dangling bond-free surface. Most attention has been drawn to high-mobility semiconducting channels or metallic quasi-Ohmic contacts to advance 2D materialbased transistors. Recently, 2D dielectrics have gained growing attention due to their ability to achieve a high dielectric constant and low equivalent oxide thickness (EOT), which is essential for enhancing gate controllability and minimizing leakage currents. Here, we introduce a topological dielectric of a BiF /Bi Se stack induced by SF plasma treatment. The topologically insulating surface of Bi Se can be functionalized with a high-k dielectric BiF , which is formed through a phase transition from Bi Se to BiF In particular, the excellent dielectric properties of the BiF /Bi Se gate stack enable sub-1-nm EOT, leading to negligible hysteresis and subthreshold swing below the Boltzmann limit of 60 mV/dec. Our experimental results indicate that a BiF /Bi Se stack is promising for various applications, such as insulation layers, embedded spacers, gate dielectrics, and photonic resonant cavities.