Thickness-Dependent Superconductor-Insulator Transition of TaN Thin Film Grown with Atomic Layer Deposition

Abstract

Atomic layer deposition (ALD) is a well-known method to grow a thin film which can ensure the uniformity and conformality of the grown film. In this work, TaN thin films with thicknesses ranging 8.9 nm to 32.6 nm were grown by using plasma enhanced ALD with Tris(diethylamido)(tert-butylimido)tantalum(TBTDET) precursor and H2 reactant. The electrical properties of grown films including carrier density, mobility, and Hall coefficient obtained from Hall effect measurements are presented. From the temperature-dependency of sheet resistance and Hall coefficient above superconducting critical temperature ~4.3 K, the thickest TaN film appeared strongly disordered with kFl ~ 0.4 and showed the unusual metallic behavior (d??/dT<0). The slope of Hall coefficient vs. sheet resistance plot was found to be more toward the strong localization limit, which would be a valid interpretation under the weak scattering assumption. Most relevantly, the critical temperature was extracted to keep decreasing as the film became thinner and thinner. From the thickness dependence of critical temperature, superconductor-insulator transition is expected to occur as the film thickness goes below ~18.5 nm