Formation of High‐Pressure Phase of Titanium Dioxide (TiO₂‐II) Thin Films by Vapor‐Liquid‐Solid Growth Process on GaAs Substrate

Abstract

In this work, the high pressure phase of titanium dioxide (TiO 2 ‐II) film is grown with vapor‐liquid‐solid (VLS) method on <100>‐GaAs substrate by utilizing the natural process‐induced‐strain, originating from the thermo‐elastic mismatch between TiO 2 and GaAs in VLS process. The mismatches in thermal expansion coefficient and elastic constant of TiO 2 and GaAs are and which incorporate a substantial amount of stress (≈GPa) during cooling from the growth temperature (500 °C). SEM imaging suggests the formation of a continuous film and cross‐sectional TEM image confirmed its high crystalline quality. XRD peaks at 2θ = 31.30 0 and 58.67 0 confirm the formation of [111] and [212]‐planes of TiO 2 ‐II phase and its chemical states are analyzed from X‐ray photoelectron spectroscopy (XPS) measurements. The bandgap of TiO 2 ‐II phase is estimated to be 2.88 eV from cathodoluminescence study for the first time which agrees satisfactorily with the theoretical predictions reported.