In situ reflection electron microscopy for investigation of surface processes on Bi2Se3(0001)

The sublimation and van der Waals (vdW) epitaxy on Bi 2 Se 3 (0001) surface have been first visualized using in situ reflection electron microscopy. When Bi 2 Se 3 (0001) surface was exposed to a Se molecular beam (up to 0.1 nm/s) and heated to ∼400°C, we observed ascending motion of atomic steps corresponding to congruent Bi 2 Se 3 sublimation. During the sublimation, grooves made by probe lithography act as sources of atomic steps: groove depth increases and generates atomic steps that move in the ascending direction away from the source. We used this phenomenon to create self-organized regularly-spaced zigzag atomic steps having 1 nm height on the Bi 2 Se 3 (0001) surface. The deposition of Bi (up to ∼0.01 nm/s) onto the Bi 2 Se 3 (0001) surface at constant Se flux (up to ∼0.1 nm/s) reversed the direction of the step flow, and vdW epitaxy was observed. The deposition of In and Se onto the Bi 2 Se 3 (0001) surface at ∼400°C led to the epitaxial growth of layered In 2 Se 3 . This vdW heteroepitaxy started with 2D island nucleation and, after 3–5 nm growth, continued with a screw-dislocation-driven formation of 3D islands. Ex situ Raman scattering measurements have shown that the grown 20-nm-thick In 2 Se 3 film exhibits vibrational modes that originate from the β-In 2 Se 3 crystal phase.