Langmuir-Blodgett fabrication of nanosheet-based dielectric films without an interfacial dead layer

Langmuir-Blodgett (LB) deposition was employed to fabricate high-κ dielectric nanofilms of titania nanosheets. The LB-based layer-by-layer approach using an atomically flat SrRuO₃ substrate is effective for the fabrication of atomically uniform and highly dense nanofilms. These films exhibited both high dielectric constant (K ∼ 123) and low leakage current density (J < 10^-7 A cm^-2) for thicknesses down to 5nm, while eliminating the size-effect problems encountered in current high-κ films. From analyses of interfacial structures by transmission electron microscopy and hard X-ray photoelectron spectroscopy, we have clarified that the films are composed of a well-ordered lamellar structure without an interfacial dead layer. According to first-principles calculations, a highly polarizable nature of titania nanosheets can bring improved dielectric properties, yielding high-κ values even in an ultrathin geometry (< nm).