Electron and photon induced selenium migration in single crystal 2H-NbSe2

Abstract

Transition metal dichalcogenides like 2H-NbSe2 exhibit remarkable electronic properties, but their performance is highly sensitive to defects, particularly selenium vacancies. Here, we demonstrate controlled migration of Se atoms from the bulk to the surface of NbSe2 single crystal, induced by heat, electron beam irradiation, and laser excitation. Using Raman spectroscopy, atomic force microscopy, and energy-dispersive x-ray spectroscopy, we identify the formation of nanosized (200–500 nm) amorphous selenium clusters on the surface, evidenced by a distinct Raman mode at 250 cm−1. Temperature-dependent studies reveal the thermally activated nature of this process, with an activation energy of 1.12 eV—significantly higher than in related dichalocogenide 1T-TiSe2, suggesting suppressed Se diffusion in NbSe2 at elevated temperatures. The results provide an estimate of the fabrication thermal budget for future electronic and optoelectronic devices utilizing NbSe2.