Annealing-tailored visible photodetection performance of Sb2S3 thin films deposited by E-beam evaporation

Abstract

Sb2S3 thin films were deposited on glass substrates by electron-beam (e-beam) evaporation and subsequently annealed at 250°C, 300°C, and 350°C in a sulfur–argon atmosphere using a rapid thermal annealing (RTA) process. The effects of annealing temperature on the structural, morphological, optical, and photodetection properties of the films were systematically investigated. X-ray diffraction (XRD) and Raman spectroscopy analyses revealed that the as-deposited Sb2S3 films were amorphous, whereas the annealed films exhibited a polycrystalline orthorhombic Sb2S3 structure with progressively improved crystallinity at higher annealing temperatures. Scanning electron microscopy (SEM) observations indicated significant grain growth following annealing, while X-ray photoelectron spectroscopy (XPS) confirmed the formation of Sb2S3 with Sb3+ chemical states and revealed a sulfur-deficient surface composition. Optical measurements showed that the optical band gap decreased from 1.95 eV for the as-deposited film to approximately 1.74 eV after annealing, which can be associated with improved crystallinity and reduced structural disorder. Photodetectors with an Ag/Sb2S3/Ag configuration were fabricated, and their photoresponse characteristics were evaluated under blue (443 nm) and red (625 nm) illumination. The device fabricated using the Sb2S3 film annealed at 350°C exhibited the highest photosensitivity values of 5553% and 6302% under blue (16 mW/cm2) and red (14 mW/cm2) illumination, respectively, together with stable switching behavior. For the same device, the maximum responsivity (R) reached 47.72 μA/W under red illumination (5 mW/cm2), while the shortest rise and decay times were 8 ms and 12 ms, respectively. In addition, the photodetector fabricated from the film annealed at 350°C achieved a maximum detectivity (D*) of 7.3 × 108 Jones under red illumination at 14 mW/cm2. The improved photodetection performance is correlated with the enhanced crystallinity, and reduced structural disorder induced by sulfur-assisted annealing. These results demonstrate that e-beam-evaporated Sb2S3 thin films are promising candidates for visible-light photodetector applications.