Texture and phase transition hysteresis in epitaxially integrated VO2 films on TiN/Si(100)

Vanadium oxide (VO2), which exhibits a metal-to-insulator (MIT) transition at 68 degrees C, has been of immense technological interest for many applications such as sensor, electro-optic, and memory devices. In this work, we demonstrate the epitaxial integration of VO2 onto Si(100) via a TiN buffer layer, which is compatible with complementary metal-oxide-semiconductor (CMOS) technology. Our study revealed that the growth of epitaxial VO2 on TiN was mediated by a thin layer of epitaxial TiO2. The orientation relationship between various layers was established to be (011)(VO2M) parallel to (110)(TiO2) parallel to (100)(TiN) parallel to (100)(Si) and [100](VO2M) parallel to [001](TiO2) parallel to [011](TiN) parallel to [011](Si). Through pole figures, reciprocal space maps (RSM), and transmission electron microscopy (TEM), we confirmed the presence of tilted rotational domains. We quantified the degree of misorientation in various VO2 films by introducing a relevant parameter, eta, determined by analyzing the (011) pole figures. We found a correlation indicating that the thermal hysteresis of the phase transition, determined from insitu temperature-dependent XRD, decreases with the degree of misorientation. This decrease in misorientation suggests the presence of more geometrically compatible grain boundaries, leading to a decrease in thermal hysteresis.