Breaking Lattice Symmetry in Highly Strained Epitaxial VO₂ Films on Faceted Nanosurface

Abstract

The lattice symmetry of strongly correlated oxide heterostructures determines their exotic physical properties by coupling the degrees of freedom between lattices and electrons, orbitals, and spin states. Systematic studies on VO 2 , a Mott insulator, have previously revealed that lattice distortion can be manipulated by the interfacial strain and electronic phase separation can emerge. However, typical epitaxial film-substrate interface strain provides a very limited range for exploring such interface-engineered phenomena. Herein, epitaxially grown VO 2 thin films on asymmetrically faceted m-plane sapphire substrates with the hill-and-valley type surfaces have been demonstrated. Interestingly, lattice symmetry breaking has been proven based on the large residual strain from the different faceted planes. By this lattice symmetry breaking, electronic phase separation and metal−insulator transition in the VO 2 films are modulated, and anisotropy in optical responses is exhibited. These results on asymmetrical interfacial engineering in oxide heterostructures open up new routes for novel functional materials design and functional electro/optic device nanofabrication.

Automated extraction of synthesis parameters of pulsed laser-deposited materials from scientific literature

“…For example, VO 2 is a metastable phase deposited using the V 2 O 5 target that shows a very narrow growth window near 10 mTorr oxygen partial pressure. [40][41][42] The difference in growth temperature for the different materials can arise due to several factors, including bonding energy, substrate crystal structure, vapor pressure, diffusion coefficient, etc. Therefore, such a database can greatly help in quickly deciding the appropriate deposition parameters for a variety of materials.…”

Self-powered VO2 phase transition based on triboelectric nanogenerator

“…[12][13][14][15][16] To decrease the critical temperature and modulate the MIT process of VO 2 , researchers have attempted various approaches, which include doping with different elements, 17,18 applying external electric elds, 19,20 and utilizing interface strain. 21,22 However, the reliance on external power sources or equipment poses a signicant drawback due to the associated high usage costs and complex operations, thus, a self-powered VO 2 phase transition modulation method is highly desired.…”

Combined Role of Substrate and Doping on the Semiconductor-to-Metal Transition of VO2 Thin Films

“…The introduction of compressive strain along the c -axis of rutile VO 2 ( c R ) tends to shorten the interatomic distance of V–V pairs, hence facilitating the transition from the monoclinic state composed of dimerized V–V pairs to the rutile state with long-range V–V chains. This effect was reported to arise from microstructure-induced strain − and from substrate-induced strain originating from the mismatch between the lattice parameters of the film and the substrate. − It could also be due to the presence of atomic and/or crystallographic defects at the interface . Unlike doping which is a bulk effect, the interfacial effects are localized within the first few atomic layers of the film.…”