Innovative FeS@Se nanostructures via pulsed laser ablation to enhance the heterojunction performance of FeS/Si photodetectors

This study investigates the effects of selenium (Se) incorporation on iron sulfide (FeS) nanoparticles synthesized via pulsed laser ablation and evaluates its impact on the performance of n-FeS/p-Si heterojunction photodetectors. The structural, morphological, optical, and chemical properties of both FeS and FeS@Se thin films were systematically analyzed. X-ray diffraction (XRD) analysis indicated that both films possess a hexagonal structure, with average crystallite sizes of 54.98 nm for FeS and 57.53 nm for FeS@Se. Scanning electron microscopy (SEM) imaging revealed that FeS has a well-dispersed nanosheet morphology, with an average particle size of 62.15 nm. In contrast, FeS@Se displayed wire-like nanostructures composed of 2D nanosheet, resulting in a larger average particle size of 105 nm. Atomic force microscopy (AFM) analysis supported these observations, showing an increase in average grain size from 81 nm for FeS to 300 nm for FeS@Se. The optical band gap decreased slightly from 2.8 eV for FeS to 2.7 eV for FeS@Se, indicating enhanced light absorption. FTIR spectroscopy revealed bond stretching frequencies for FeS at 697 and 700 \({\hbox {cm}}^{-1}\), while Se-related bonds could not be distinctly identified due to overlapping frequency ranges. The incorporation of selenium (Se) significantly improved the performance of the photodetector. The responsivity increased from 0.18 A/W at 450 nm for iron sulfide (FeS) to 0.41 A/W at 550 nm for FeS@Se. Additionally, the detectivity improved from \(1.08 \times 10^{10}\) Jones to \(2.39 \times 10^{10}\) Jones. These results demonstrate the potential of incorporating Se to advance FeS-based photodetector technology.