Fabrication of Bi₄X₄ Field Effect Transistors with Ohmic Contact

The novel one-dimensional van der Waals materials Bi₄X₄ (X=Bi, I) constitute a promising platform for realizing room temperature quantum spin hall (QSH) effect, due to their large bulk band gap and topologically protected edge channels. Though the theoretical prediction has been confirmed by recent scanning tunneling microscopy and the angle-resolved photoemission spectroscopy, transport demonstration of the QSH state has been elusive, largely due to the challenge of achieving ohmic contact. In this talk, we will discuss fabrication protocols of Bi4X4 field effect transistors, and compare several experimental techniques of making electrical contacts to these materials.