1. Emerging oxidized and defective phases in low-dimensional CrCl3
- Author
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Dario Mastrippolito, Roberto Gunnella, Shafaq Kazim, Luca Lozzi, Judyta Strychalska-Nowak, Luca Ottaviano, Gianluca D'Olimpio, Jing Wang, Mushtaq Ali, Andrea Di Cicco, Gianni Profeta, Tomasz Klimczuk, Robert J. Cava, Antonio Politano, Anna Sgarlata, S. Palleschi, Jinjin Yang, and Faming Gao
- Subjects
Settore FIS/03 ,Materials science ,Band gap ,Photoemission spectroscopy ,Scanning tunneling spectroscopy ,General Engineering ,Analytical chemistry ,Bioengineering ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Amorphous solid ,X-ray photoelectron spectroscopy ,Transmission electron microscopy ,Monolayer ,General Materials Science ,Density functional theory ,0210 nano-technology - Abstract
Two-dimensional (2D) magnets such as chromium trihalides CrX3 (X = I, Br, Cl) represent a frontier for spintronics applications and, in particular, CrCl3 has attracted research interest due its relative stability under ambient conditions without rapid degradation, as opposed to CrI3. Herein, mechanically exfoliated CrCl3 flakes are characterized at the atomic scale and the electronic structures of pristine, oxidized, and defective monolayer CrCl3 phases are investigated employing density functional theory (DFT) calculations, scanning tunneling spectroscopy (STS), core level X-ray photoemission spectroscopy (XPS), and valence band XPS and ultraviolet photoemission spectroscopy (UPS). As revealed by atomically resolved transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis, the CrCl3 flakes show spontaneous surface oxidation upon air exposure with an extrinsic long-range ordered oxidized O–CrCl3 structure and amorphous chromium oxide formation on the edges of the flakes. XPS proves that CrCl3 is thermally stable up to 200 °C having intrinsically Cl vacancy-defects whose concentration is tunable via thermal annealing up to 400 °C. DFT calculations, supported by experimental valence band analysis, indicate that pure monolayer (ML) CrCl3 is an insulator with a band gap of 2.6 eV, while the electronic structures of oxidized and Cl defective phases of ML CrCl3, extrinsically emerging in exfoliated CrCl3 flakes, show in-gap spin-polarized states and relevant modifications of the electronic band structures.
- Published
- 2021