High-Crystallinity Epitaxial Sb₂Se₃ Thin Films on Mica for Flexible Near-Infrared Photodetectors

The V-VI binary chalcogenide, Sb₂Se₃, has attracted considerable attention for its applications in thin film optoelectronic devices because of its unique 1D structure and remarkable optoelectronic properties. Herein, we report an Sb₂Se₃ thin film epitaxially grown on a flexible mica substrate through a relatively weak (van der Waals) interaction by vapor transport deposition. The epitaxial Sb₂Se₃ thin films exhibit a single (120) out-of-plane orientation and a 0.25° full width at half-maximum of (120) rocking curve in X-ray diffraction, confirming the high crystallinity of the epitaxial films. The Sb₂Se₃(120) plane is epitaxially aligned on mica(001) surface with the in-plane relationship of Sb₂Se₃[2̅10]//mica[010] and Sb₂Se₃[001]//mica[100]. Compared to the photodetector made of a nonepitaxial Sb₂Se₃ film, the photocurrent of the epitaxial Sb₂Se₃ film photodetector is almost doubled. Furthermore, because of the flexibility and high sensitivity of the epitaxial Sb₂Se₃ film photodetector on mica, it has been successfully employed to detect the heart rate of a person. These encouraging results will facilitate the development of epitaxial Sb₂Se₃ film-based devices and potential applications in wearable electronics.