Dislocation annihilation in epitaxial silicene formed on diboride thin films

抄録

Two-dimensional (2D) materials formed epitaxially on single-crystal surfaces can have stress domains originating from the lattice mismatch between the lattices of 2D material and substrate surface. Epitaxial silicene sheet formed spontaneously on epitaxial ZrB₂(0001) thin film grown on Si(111) substrate has a characteristic domain structure [1], which also seems to exist in those formed by Si deposition on ZrB₂(0001) single crystal surface [2]. Scanning tunneling microscope (STM) observations of ZrB₂(0001) thin film surface under ultrahigh vacuum, after natural oxide removal, reveal stripe domains with width of approximately 3 nm [1]. The stripe domain boundaries running along arm-chair directions in silicene honeycomb lattice are part of the continuous, buckled honeycomb lattice which contain partial dislocations [3]. The transformation process of this stripe domains into a “single-domain” through adsorption of a small amount of silicon atoms [4] was monitored by in-situ real time STM observations at room temperature to investigate how dislocations react and eventually annihilate in a strained, buckled honeycomb lattice. The observation revealed the stepwise reactions of partial dislocations leading to the nucleation of a single-domain island, followed by the island extension through propagation of edge dislocations at its frontiers. The identification of dislocation annihilation process in epitaxial silicene sheet provides insights into how crystallographic defects can be healed in 2D materials.

[1] A. Fleurence et al., Phys. Rev. Lett., 108, 245501 (2012).

[2] T. Aizawa, S. Suehara, and S. Otani, J. Phys.: Condens. Matter, 27, 305002 (2015).

[3] A. Fleurence and Y. Yamada-Takamura, 2D Mater., 8, 045011 (2021).

[4] A. Fleurence et al., App. Phys. Lett., 108, 151902 (2016).