Atomic-Scale Metal-Insulator Transition in SrRuO3 Ultrathin Films Triggered by Surface Termination Conversion

Han Gyeol Lee; Lingfei Wang; Liang Si; Xiaoyue He; Daniel G Porter; Jeong Rae Kim; Eun Kyo Ko; Jinkwon Kim; Sung Min Park; Bongju Kim; Andrew Thye Shen Wee; Alessandro Bombardi; Zhicheng Zhong; Tae Won Noh

doi:10.1002/adma.201905815

Atomic-Scale Metal-Insulator Transition in SrRuO₃ Ultrathin Films Triggered by Surface Termination Conversion

Adv Mater. 2020 Feb;32(8):e1905815. doi: 10.1002/adma.201905815. Epub 2019 Dec 12.

Authors

Han Gyeol Lee^{1

2}, Lingfei Wang^{1

2}, Liang Si^{3

4}, Xiaoyue He^{5

6}, Daniel G Porter⁷, Jeong Rae Kim^{1

2}, Eun Kyo Ko^{1

2}, Jinkwon Kim^{1

2}, Sung Min Park^{1

2}, Bongju Kim^{1

2}, Andrew Thye Shen Wee⁵, Alessandro Bombardi⁷, Zhicheng Zhong^{3

8}, Tae Won Noh^{1

2}

Affiliations

¹ Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea.
² Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea.
³ Key Laboratory of Magnetic Materials and Devices & Zhejiang Province, Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, P. R. China.
⁴ Institut für Festkörperphysik, Vienna, 1040, Austria.
⁵ Department of Physics, National University of Singapore, Singapore, 117542, Singapore.
⁶ Songshan Lake Materials Laboratory, Dongguan, 523808, P. R. China.
⁷ Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK.
⁸ China Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China.

PMID: 31830343
DOI: 10.1002/adma.201905815

Abstract

The metal-insulator transition (MIT) in transition-metal-oxide is fertile ground for exploring intriguing physics and potential device applications. Here, an atomic-scale MIT triggered by surface termination conversion in SrRuO₃ ultrathin films is reported. Uniform and effective termination engineering at the SrRuO₃ (001) surface can be realized via a self-limiting water-leaching process. As the surface termination converts from SrO to RuO₂ , a highly insulating and nonferromagnetic phase emerges within the topmost SrRuO₃ monolayer. Such a spatially confined MIT is corroborated by systematic characterizations on electrical transport, magnetism, and scanning tunneling spectroscopy. Density functional theory calculations and X-ray linear dichroism further suggest that the surface termination conversion breaks the local octahedral symmetry of the crystal field. The resultant modulation in 4d orbital occupancy stabilizes a nonferromagnetic insulating surface state. This work introduces a new paradigm to stimulate and tune exotic functionalities of oxide heterostructures with atomic precision.

Keywords: SrRuO3; epitaxial ultrathin films; ferromagnetism; metal-insulator transition; surface termination engineering.

Abstract

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