Effect of Cu intercalation on humidity sensing properties of Bi2Se3 topological insulator single crystals

Abstract

Here we report the self-flux method-based synthesis of Cu_xBi₂Se₃ (x = 0, 0.13 and 0.25) topological insulator (TI) single crystals with high phase purity for humidity sensing for the first time. The samples were thoroughly characterized using XRD, FESEM, Raman, etc. The chemi-resistive humidity sensing performance of the obtained Cu_0.25Bi₂Se₃ single crystal exhibits high sensitivity (∼849%) with decent response time (24 s) and recovery (25 s) time, negligible hysteresis (<1%) and excellent stability within an 8–97% relative humidity (RH) range at room temperature. The Freundlich isotherm model shows improved adsorption parameters (k and α) for Cu_xBi₂Se₃ (x = 0.25) over the entire RH region demonstrating the improved sensing performance of Bi₂Se₃ TIs with Cu intercalation. The effect of Cu intercalation in Bi₂Se₃ was investigated using the Langmuir adsorption isotherm (LA) model signifying the role of faster conduction of water vapour over the surface with a single active site for the adsorption–desorption process. The current experimental results suggest that Cu_xBi₂Se₃ TIs hold immense potential for important applications related to sensing.