Hybrid MBE Growth and Characterization of Single Crystalline Anatase TiO₂ Membranes

Epitaxially grown oxide membranes provide an excellent platform to explore their physical properties without strain, chemical and electrostatic constraints imposed by the rigid substrate. Among binary oxides, anatase TiO₂ is of particular interest, owing to its excellent electronic and optical properties such as wide band gap (~ 3.2 eV), polaronic transport with high room-temperature mobility, and high refractive index, making it an excellent candidate for photocatalyst and antireflection coating. Anatase TiO₂ crystallizes in a tetragonal structure with lattice parameters a = b = 3.78 Å and c = 9.51 Å. Here, we demonstrate the epitaxial growth of anatase TiO₂ films using hybrid MBE on a water-soluble SrO sacrificial layer grown epitaxially on LaAlO₃(001) substrates. Dissolving SrO layer in deionized water yields single crystalline, anatase TiO₂ membranes with a bulk-like out-of-plane lattice parameter of 9.497 ± 0.005 Å. Atomic Force Microscopy confirm smooth surface morphology. We will present the dielectric, optical and transport properties, of these membranes as a function of membrane thickness.