SrHfO₃ Films and Heterostructures Grown by Hybrid Molecular Beam Epitaxy

SrHfO₃ is a band insulating dielectric perovskite oxide with an extremely large bandgap (E_g = 6.2 eV). According to density functional theory (DFT) modeling, SrHfO₃ will not accept electrons from any other transition metal perovskite oxide and thus will act as a good dielectric barrier and atmospheric capping layer in oxide heterostructures. Some works have predicted and observed that epitaxial strain can stabilize the octahedral tilting of SfHfO₃ and produce a metastable ferroelectric phase. Epitaxial films of SrHfO₃ were grown on GdScO₃ and SrTiO₃ using hybrid molecular beam epitaxy, where Hf was introduced using Tetrakis(dimethylamino)hafnium [Hf(N(CH3)2)4] and growth was monitored via Reflected High Energy Electron Diffraction. Stoichiometry and surface termination were characterized by in situ X-ray Photoelectron Spectroscopy and Rutherford Back Scattering to examine the growth window for the material. X-ray diffraction, scanning transmission electron microscopy, and second harmonic generation studies were performed to examine the possibility of ferroic distortions in the films due to strain or formation of epitaxial heterostructures with SrTiO₃. We also examine the functionality of SrHfO₃ as an atmospheric capping layer in oxide heterostructures.