Oxygen Vacancy Induced Room-Temperature Metal–Insulator Transition in Nickelate Films and Its Potential Application in Photovoltaics

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• 作者：Le Wang ; Sibashisa Dash ; Lei Chang ; Lu You ; Yaqing Feng ; Xu He ; Kui-juan Jin ; Yang Zhou ; Hock Guan Ong ; Peng Ren ; Shiwei Wang ; Lang Chen ; Junling Wang
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：April 20, 2016
• 年：2016
• 卷：8
• 期：15
• 页码：9769-9776
• 全文大小：627K
• 年卷期：0
• ISSN：1944-8252

文摘

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_2g⁶e_g² 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.