Direct Observation of Self-Intercalation Driven 2D-to-3D Phase Transition in VSe2

Jianchu Chen; Jianwei Zhang; Kai-Qi Wang; Jun Zeng; Yuhan Du; Xiang Yuan; Ke Qu; Zhenzhong Yang; Chungang Duan

doi:10.1021/acs.nanolett.5c05757

Direct Observation of Self-Intercalation Driven 2D-to-3D Phase Transition in VSe₂

Nano Lett. 2026 Jan 14;26(1):589-596. doi: 10.1021/acs.nanolett.5c05757. Epub 2025 Dec 22.

Authors

Jianchu Chen¹, Jianwei Zhang¹, Kai-Qi Wang¹, Jun Zeng¹, Yuhan Du², Xiang Yuan², Ke Qu¹, Zhenzhong Yang¹, Chungang Duan^{1

3}

Affiliations

¹ Key Laboratory of Polar Materials and Devices (MOE), Department of Electronics, and Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China.
² State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China.
³ Collaborative Innovation Center of Extreme Optics, Shanxi University, Shanxi 030006, China.

PMID: 41427604
DOI: 10.1021/acs.nanolett.5c05757

Abstract

Precise control of phase transitions is essential for tuning properties of two-dimensional (2D) materials. Self-intercalation can modulate structural and electronic states in layered systems, yet its microscopic mechanism remains unclear owing to scarce atomic-scale in situ evidence. Using atomic-resolution scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectroscopy (EDS), we directly visualize the self-intercalation-driven conversion from the 2D 1T phase to a three-dimensional (3D) self-intercalated phase in VSe₂. In situ manipulation reveals atomic structural evolution as vanadium ions migrate into van der Waals (vdW) gaps during the 2D-to-3D transition. Density functional theory (DFT) calculations confirm the stability and intrinsic ferromagnetism of the 3D phase. This work establishes a structural evolution model for the 2D-to-3D transition in VSe₂, elucidates the atomic mechanism of self-intercalation-induced phase transitions in transition metal dichalcogenides (TMDs), and provides a mechanistic foundation for rational phase engineering of low-dimensional magnetic materials.

Keywords: Self-intercalation; VSe2; ferromagnetism; in situ TEM; phase transition.