Twin-free (1 1 1)-oriented epitaxial Nd2Hf2O7 thin films on Ge(1 1 1) for high-k dielectrics

Abstract

Twin-free epitaxial cubic Nd2Hf2O7 (NHO) thin films as high dielectric constant (high-k) materials have been grown on Ge(1 1 1) substrates by pulsed laser deposition. Reflection high-energy electron diffraction and x-ray diffraction show that the predominant orientation of the fluorite phase NHO film grown at 650 °C is (1 1 1)NHO//(1 1 1)Ge and . High-resolution transmission electron microscopy observation indicates a smooth interface and a sight interfacial layer (IL) between Ge and NHO thin film. X-ray photoelectron spectroscopy results suggest that the IL of the NHO/Ge stack is composed of GeOx (0 < x < 2). The electrical properties of the films, as examined by capacitance–voltage, conductance–voltage and current–voltage measurements, exhibit a dielectric constant of ∼16 with a leakage current density of 6 mA cm−2 at 1 V.