Engineering the synthesis and electronic properties of IrO₂ using heterostructure design

IrO₂ is a strong spin-orbit coupled material with intriguing electronic, spintronic and topological properties. However, it’s synthesis and manipulation of electronic properties, particularly using Molecular Beam Epitaxy (MBE), has been less explored. Here, using hybrid MBE, we demonstrate synthesis of high quality epitaxially strained IrO₂ thin films on different facets of single crystalline TiO₂ substrates. The resulting films were atomically smooth as observed by atomic force microscopy with an average root mean square roughness ~ 2 Å, ideal for surface sensitive heterostructure synthesis and device performance. The films grown on TiO₂ (110) substrates showed a thickness-dependent variation in in-plane resistance anisotropy, likely due to anisotropic strain-relaxation induced band structure changes. We also observed a previously unreported non-linear Hall effect in these IrO₂ thin films as a function of film thickness, a careful analysis of which reveals multi-band transport with minority carrier mobilities exceeding 3000 cm²/V.s at 1.8 K. Further, using heterostructure design, we synthesized ultra-thin IrO₂ films with persistent metallicity, opening new possibilities for applications in nanoelectronics, electrocatalysis and spintronics using IrO₂ heterostructures.