Epitaxial integration of TiO2 with Si(100) through a novel approach of oxidation of TiN/Si(100) epitaxial heterostructure

Abstract

In this study, we provide a novel approach to the epitaxial integration of TiO 2 with Si(100) and investigate the defect mediated ferromagnetism in TiO 2 structure. Epitaxial TiO 2 thin films were grown on a TiN/Si(100) epitaxial heterostructure through oxidation of TiN where a single crystalline rutile-TiO 2 (r-TiO 2 ) with a [110] out-of-plane orientation was obtained. The epitaxial relationship is determined to be TiO 2 (1 0)||TiN(100) and TiO 2 (110)||TiN(110). We rationalized this epitaxy using the domain matching epitaxy paradigm. First TiN is grown epitaxially on Si(100). Subsequently, TiN/Si(100) samples are oxidized to create r-TiO 2 /TiN/Si(100) epitaxial heterostructures. The details of the mechanism behind the oxidation of single crystalline TiN to TiO 2 was investigated using atomic scale high resolution electron microscopy techniques. Defects introduced to the heterostructure during oxidation caused ferromagnetism in TiO 2 thin film which is reversible and can be tuned by controlling oxygen partial pressure. The source of magnetization is correlated with the presence of oxygen vacancy leading to introduction of two localized states; hybrid and polaron among neighboring Ti atoms, and titanium vacancy providing four holes to form molecular oxygen. We present structure property correlations and its impact on the next generation solid state devices.

Electrical Transition in Isostructural VO2 Thin-Film Heterostructures

“…The magnetic properties were measured using a vibrating superconducting quantum interference device (SQUID) magnetometer 49–51 .…”

Vacancy-Driven Robust Metallicity of Structurally Pinned Monoclinic Epitaxial VO2 Thin Films

“…Thin film heterostructures were deposited using a KrF excimer laser with the frequency of 5 Hz and energy of 3.5 mJ/cm 2 . − The NiO layer was grown at 700 °C and 10 × 10 –4 Torr oxygen pressure, and the VO 2 film was deposited at 550 °C and 1.2 × 10 –2 Torr oxygen pressure . The vacuum-annealing procedure was performed at 1 × 10 –7 and 450 °C for 2 h.…”

Mechanism of strain relaxation: key to control of structural and electronic transitions in VO2 thin-films

“…It is important to note that, tensile strain at the interface moderately increases the kinetic barrier for dislocation nucleation. Even though thermodynamically the h c is calculated at 15 nm, kinetically dislocations do not form up to a bit higher value due to enhanced dislocation nucleation barrier enforced by the tensile strain [18,24].…”