Manipulating the metal-insulator transition in SrVO₃ ultrathin oxide films by strain engineering

Metal-insulator transitions (MITs) in strongly correlated perovskite oxides have been extensively explored, particularly in reduced-dimensional systems such as thin oxide films. Notably, SrVO₃ (SVO) exhibits emergent phenomena as film thickness approaches the two-dimensional limit. Our previous studies on SrTiO₃ (STO)-capped SVO films revealed a transition from a Mott insulating state at 6 unit cells (u.c.) to metallic behavior at 1O u.c. As the thickness decreases, spectral weight shifts from the quasiparticle (QP) peak to the lower Hubbard band (LHB), with complete suppression of the QP peak and the opening of a charge gap, signaling the onset of the Mott insulating state. This transition is driven by reduced electron hopping in ultrathin films, which decreases the effective bandwidth and enhances short-range Coulomb repulsion. Alternatively, oxygen vacancies near the substrate interface can induce MITs through disorder, structural distortions, and electron localization. We propose that lateral tensile and compressive strain offers an additional means to modulate the balance between kinetic energy and local Coulomb repulsion.
In this study, we report the synthesis of coherently strained and stoichiometric SVO thin films on substrates with varying lattice constants via pulsed laser deposition (PLO). Using hard and soft X­ray photoelectron spectroscopy and transport measurements, we demonstrate that the MIT in SVO thin films is finely tunable by both film thickness and substrate-induced strain. X-ray linear dichroism (XLD) further reveals that strain-induced changes in orbital occupancy underlie this MIT behavior. Additionally, we observe emergent phenomena at the SVO/LSAT interface, driven by mixed cation occupation. These findings provide deeper insights into Mott transitions and highlight the importance of strain and interfacial effects in controlling electronic phases in correlated oxides.