Two-step large-area synthesis of Bi2Se3 topological insulator thin films via bismuth evaporation and selenization

Abstract

Bi₂Se₃ is recognized as one of the most promising topological insulators, with substantial potential for industrial applications, particularly as a qubit in quantum computing. Realizing large-area growth using cost-effective methods is crucial for practical applications. This study presents an innovative approach for fabricating high-quality large-area Bi₂Se₃ thin films by combining Bi thermal evaporation with cracker selenization, which inherently supports scalability. The amorphous precursor—a Bi film capped with a Se layer—reacts with highly reactive cracked Se, forming crystalline Bi₂Se₃ thin films with layered structures. Prolonged selenization enhances the crystallinity of the Bi₂Se₃ thin films and significantly reduces their oxygen content by effectively substituting the O atoms with Se atoms. Thicker precursors require extended selenization to improve their crystallinity and are more susceptible to stress. Electrical transport measurements of Bi₂Se₃ films formed via selenization for 8 h reveal a long phase coherence length of >375 nm and a single surface state with a spin texture, which are unique properties of topological insulators. Uniform physical and optical properties are achieved across a substrate with a large 4-in diameter under optimized conditions. This novel method exhibits great potential for the industrial fabrication of high-quality large-area Bi₂Se₃ topological insulator thin films.