Gate-tunable two-dimensional ITO epsilon-near-zero materials fabricated by liquid metal printing

Finely tuned optical thin films and metasurfaces allow for precise control of optical phenomena at the light matter interface. Epsilon Near Zero (ENZ) materials with a particular frequency where their electrical permittivity approaches zero can support ENZ modes which leads to large electric field intensity enhancement within the film and unique linear/nonlinear optical properties. In this work, we utilize two-dimensional ITO ENZ material as active material to develop highly tunable devices in the NIR regime via thin film transistor field effect approach. Previously studied ENZ thin films containing ITO layer thicknesses in the dozens to hundreds of nanometers range result in weak field confinement and electrical tunability. By utilizing a liquid metal printing technique, we fabricated monolayers and bilayers of ITO with atomical layer thicknesses of 1.5 and 3 nm respectively, confirmed by atomic force microscopy. This study is an important step in developing ultrathin tunable ENZ devices for linear, nonlinear, and quantum phenomena.