Structure and photoemission spectroscopy of strain-controlled metal-insulator transition in NdNiO3 thin films

Abstract

We study epitaxial NdNiO3 thin films on NdGaO3(001) single-crystal substrates grown using a pulsed-laser deposition method. The films show a clear first-order metal-insulator transition (MIT) at TMI∼240 K, which is significantly higher than TMI∼190 K in bulk NdNiO3. The x-ray reciprocal space map shows in-plane tensile and out-of-plane compressive strain, stabilizing the more distorted NdNiO3 thin films with the higher transition temperature. Hard x-ray photoemission shows changes across the MIT and the bandwidth-controlled charge-transfer gap opens due to the reduced p-d hybridization in the low-temperature insulating phase.