Explore of exfoliable multifunctional high-k two-dimensional oxides

As the continuing down-scaling of field-effect transistors (FETs) in more-than-Moore integrated circuits, finding new functional two-dimensional (2D) materials with a higher dielectric constant (high-k) serve as gate dielectrics is critical. Here, we identify dozens of binary 2D oxides by screening potentially exfoliable bulk metal oxides despite of their non-layered structures followed by simulation of the exfoliation process. For dynamically stable materials, we fully characterize their static dielectric constants and electronic structures, among which GeO2(011)/(101)/(1-11) 2D oxides exhibit unusually high k values (85-99), being much higher than the k of the currently highly regarded 2D dielectrics CaF2 (k ~6) and \b{eta}-Bi2SeO5 (k ~22), together with band gap of 3.3 eV. We further design 2D high-k oxides/2D semiconductors (such as MoS2) heterostructures, and determine by DFT calculations whether they can form Van der Waals interfaces to evaluate their compatibility as gate dielectrics in 2D FETs. In addition to dielectric properties, we also explore magnetic and mechanical properties of potentially exfoliable 2D oxides, revealing a number of functional materials that can be studied experimentally, notably including ferromagnetic half semiconductors, non-magnetic spintronic materials, flexible high-k 2D oxides, and auxetic monolayers.