Tuning critical phase transition in VO2 via interfacial control of normal and shear strain

Abstract

Interface strain plays a key role in creating the emergent functional properties of heteroepitaxially correlated materials. Strain that originates from the lattice mismatch of thin films and substrates has been widely studied to support the creation of desired functionalities. However, the shear strain induced by the symmetry mismatch of heterostructures has rarely been considered. Here, we report evidence of twin domains of stabilized vanadium dioxide (VO2) epitaxial films grown on sapphire substrates with a miscut along the a-plane. A systematic investigation of lattice variations, including lattice rotations and lattice distortions, reveals that both normal strain and shear strain can be manipulated by vicinal sapphire surfaces using different miscut angles. Consequently, the critical phenomenon of metal-insulator transitions (MITs) in VO2 epitaxial films is strongly coupled with lattice variations. A significantly sharpened MIT transition, over four orders of magnitude in resistance change, is also achieved by controlling interfacial shear strain. Our results demonstrate that the degree of freedom of shear lattice deformation opens the door to fine-tune the critical properties of heterostructures of strongly correlated oxides to aid in the development of electronic devices.