Epitaxial Growth of Bi₂Se₃ Thin Films by Thermal Evaporation for the Application of Electrochemical Biosensors

Bi₂Se₃ is a typical topological material with the gapless surface state, which has many potential applications. In this work, high-quality Bi₂Se₃ thin films are prepared by co-evaporating bismuth and selenium on (100) silicon substrate, followed by in-situ annealing process. The key parameters are optimized, including growth temperature and the flux ratio of Bi and Se. The crystal orientation and quality of the thin films are characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. Furthermore, Bi₂Se₃ thin films are employed as the working electrode of the biosensor, and their sensitive detection of SARS-CoV-2 characteristic gene fragments in the COVID-19 epidemic is investigated. The cyclic voltammetry, square wave voltammetry, and electrochemical impedance spectroscopy demonstrate that the DNA biosensor is successfully constructed based on Bi₂Se₃ thin films. This study develops a method of the large-scale homogeneous Bi₂Se₃ thin films growth by thermal evaporation technology, which has great application potential in electrochemical biosensors.