title: Oxygen Vacancy Induced Room-Temperature Metal-Insulator Transition in Nickelate Films and Its Potential Application in Photovoltaics.
abstract: Oxygen vacancy is intrinsically coupled with magnetic, electronic, and transport properties of transition-metal oxide materials and directly determines their multifunctionality. Here, we demonstrate reversible control of oxygen content by postannealing at temperature lower than 300 °C and realize the reversible metal-insulator transition in epitaxial NdNiO₃ films. Importantly, over 6 orders of magnitude in the resistance modulation and a large change in optical bandgap are demonstrated at room temperature without destroying the parent framework and changing the p-type conductive mechanism. Further study revealed that oxygen vacancies stabilized the insulating phase at room temperature is universal for perovskite nickelate films. Acting as electron donors, oxygen vacancies not only stabilize the insulating phase at room temperature, but also induce a large magnetization of ∼50 emu/cm³ due to the formation of strongly correlated Ni²⁺ t(2g)⁶e(g)² states. The bandgap opening is an order of magnitude larger than that of the thermally driven metal-insulator transition and continuously tunable. Potential application of the newly found insulating phase in photovoltaics has been demonstrated in the nickelate-based heterojunctions. Our discovery opens up new possibilities for strongly correlated perovskite nickelates.
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University , 639798, Singapore.
authors.forename: Le
authors.initials: L
authors.lastname: Wang
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University , 639798, Singapore.
authors.forename: Sibashisa
authors.initials: S
authors.lastname: Dash
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University , 639798, Singapore.
authors.forename: Lei
authors.initials: L
authors.lastname: Chang
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University , 639798, Singapore.
authors.forename: Lu
authors.initials: L
authors.lastname: You
authors.affiliation: Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China.
authors.forename: Yaqing
authors.initials: Y
authors.lastname: Feng
authors.affiliation: Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China.
authors.forename: Xu
authors.initials: X
authors.lastname: He
authors.affiliation: Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China.|Collaborative Innovation Center of Quantum Matter , Beijing 100190, China.
authors.forename: Kui-juan
authors.initials: KJ
authors.lastname: Jin
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University , 639798, Singapore.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Temasek Laboratories@NTU, Nanyang Technological University , 637553, Singapore.
authors.forename: Hock Guan
authors.initials: HG
authors.lastname: Ong
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University , 639798, Singapore.
authors.forename: Peng
authors.initials: P
authors.lastname: Ren
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University , 639798, Singapore.
authors.forename: Shiwei
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Physics, South University of Science and Technology of China , Shen Zhen 518055, China.
authors.forename: Lang
authors.initials: L
authors.lastname: Chen
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University , 639798, Singapore.
authors.forename: Junling
authors.initials: J
authors.lastname: Wang
keywords: heterojunction; metal−insulator transition; nickelate thin films; oxygen vacancy; photovoltaics