Titanium Self-Intercalation Induced Formation of Orthogonal (1 × 1) Edge/Surface Reconstruction in 1T-TiSe<sub>2</sub>: Atomic Scale Dynamics and Mechanistic Study.

He, Daliang; Zheng, Yonghui; Ding, Degong; Ma, Hao; Zhang, Aixinye; Cheng, Yan; Zhao, Wen; Jin, Chuanhong · Nano Lett · 2024

basic_science · Level V

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Abstract

Edges and surfaces play indispensable roles in affecting the chemical-physical properties of materials, particularly in two-dimensional transition metal dichalcogenides (TMDCs) with reduced dimensionality. Herein, we report a novel edge/surface structure in multilayer 1T-TiSe<sub>2</sub>, i.e., the orthogonal (1 × 1) reconstruction, induced by the self-intercalation of Ti atoms into interlayer octahedral sites of the host TiSe<sub>2</sub> at elevated temperature. Formation dynamics of the reconstructed edge/surface are captured at the atomic level by <i>in situ</i> scanning transmission electron microscopy (STEM) and further validated by density functional theory (DFT), which enables the proposal of the nucleation mechanism and two growth routes (zigzag and armchair). Via STEM-electron energy loss spectroscopy (STEM-EELS), a chemical shift of 0.6 eV in Ti L<sub>3,2</sub> is observed in the reconstructed edge/surface, which is attributed to the change of the coordination number and lattice distortion. The present work provides insights to tailor the atomic/electronic structures and properties of 2D TMDC materials.