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Strain‐Mediated High Conductivity in Ultrathin Antiferromagnetic Metallic Nitrides
Author(s) -
Jin Qiao,
Cheng Hu,
Wang Zhiwen,
Zhang Qinghua,
Lin Shan,
Roldan Manuel A.,
Zhao Jiali,
Wang JiaOu,
Chen Shuang,
He Meng,
Ge Chen,
Wang Can,
Lu HuiBin,
Guo Haizhong,
Gu Lin,
Tong Xin,
Zhu Tao,
Wang Shanmin,
Yang Hongxin,
Jin Kuijuan,
Guo ErJia
Publication year - 2021
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.202005920
Subject(s) - materials science , nitride , conductivity , condensed matter physics , thin film , epitaxy , fermi level , strain (injury) , electrical resistivity and conductivity , optoelectronics , nanotechnology , layer (electronics) , medicine , chemistry , physics , engineering , quantum mechanics , electrical engineering , electron
Strain engineering provides the ability to control the ground states and associated phase transition in epitaxial films. However, the systematic study of the intrinsic character and strain dependency in transition‐metal nitrides remains challenging due to the difficulty in fabricating stoichiometric and high‐quality films. Here the observation of an electronic state transition in highly crystalline antiferromagnetic CrN films with strain and reduced dimensionality is reported. By shrinking the film thickness to a critical value of ≈ 30 unit cells, a profound conductivity reduction accompanied by unexpected volume expansion is observed in CrN films. The electrical conductivity is observed surprisingly when the CrN layer is as thin as a single unit cell thick, which is far below the critical thickness of most metallic films. It is found that the metallicity of an ultrathin CrN film recovers from insulating behavior upon the removal of the as‐grown strain by the fabrication of freestanding nitride films. Both first‐principles calculations and linear dichroism measurements reveal that the strain‐mediated orbital splitting effectively customizes the relatively small bandgap at the Fermi level, leading to an exotic phase transition in CrN. The ability to achieve highly conductive nitride ultrathin films by harnessing strain‐control over competing phases can be used for utilizing their exceptional characteristics.