Formation mechanism of 2a × 2a long-range ordered structure in 1T-TiSe2 induced by electron beam irradiation and its spontaneous enlargement

Abstract A long-range ordered (LRO) structure with 2a × 2a periodicity is formed in 1T-TiSe2 flakes by electron beam irradiation. Transmission electron microscopy shows that the LRO structure is not only formed in the area irradiated by the electron beam, but also in the adjacent unirradiated area after the electron beam irradiation. We propose that the formation of the LRO structure is triggered by electron excitation to the non-bonding orbital of 1T-TiSe2 due to inelastic electron scattering. We consider that the LRO structure is spread spontaneously to the adjacent area by a chemical chain reaction due to the electron transfer.