Epitaxial Growth and Structural Properties of Bi(110) Thin Films on TiSe₂ Substrates

We report the growth and structural properties of Bi thin films on TiSe₂ substrates by using a low-temperature scanning tunneling microscope. Extended Bi(110) thin films are formed on the TiSe₂ substrates and adopt a distorted black-phosphorus structure at room temperature (RT). The diagonal of the Bi(110) rectangular unit cell is parallel to the close-packed direction of the top-layer Se atoms of the TiSe₂ substrates, resulting in the formation of a stripe-shaped commensurate moiré pattern with a periodicity of 38.5 Å at RT. Meanwhile, the charge density wave phase transition of the TiSe₂ substrate and the different coefficients of thermal expansion of Bi(110) and TiSe₂ lead to the formation of a quasi-hexagonal incommensurate moiré pattern with a periodicity of 14.5 Å at 77 K. In particular, the combination of domains with twisting angles of 30° or 60° results in the formation of various domain boundaries. Our work is very helpful for understanding and tuning the structural and electronic properties of epitaxial Bi(110) thin films.