Synthesis of HgI2 Nanoparticles and Nanorods by Laser Ablation in Liquid for Photodetector Applications: Effect of Laser Fluence

In this study, mercury iodide (HgI₂) nanoparticles (NPs) were synthesized by pulsed laser ablation in ethanol at laser fluences of 22.9, 33.1, and 43.3 J/cm². The effect of laser fluence on the structural and optical properties of HgI₂ NPs was studied. X-ray diffraction findings reveal that all synthesized HgI₂ samples were polycrystalline in nature with orthorhombic structure. Absorption peak was appeared at 474 nm and the optical energy gap of HgI₂ NPs decreases from 2.13 to 2.05 eV as laser fluence increased from 22.9 to 43.3 J/cm². Zeta potential (ZP) results confirm that the nanoparticles synthesized at 22.9 and 33.1 J/cm² have high degree of stability. Fluorescence measurements show the presence of several emission bands. Raman spectra of HgI₂ NPs show the presence of six vibration modes centered at 15, 29, 37, 44, 51, and 70 cm^?1. Fourier transform infrared (FT-IR) results show the presence of two bonds, namely, C–O and Hg-I. Transmission Electron Microscope (TEM) results showed that the formation of spherical nanoparticles for sample prepared at 22.9 J/cm², 25–75 nm in size. While the nanoparticles synthesized with 33.1 and 43.3 J/cm² exhibit nanorods and nanotubes morphologies, respectively. The dark I–V characteristics of β-HgI₂ NPs/Si heterojunction photodetectors show rectification properties and the junction quality depends on the laser fluence and the best junction characteristics was obtained for heterojunction prepared at 33.1 J/cm². The white light photosensitivity of the HgI₂/p-Si photodetectors was measured at reverse bias under different intensities. The maximum responsivity reached was 3.39A/W at 450 nm for photodetector prepared at 33.1 J/cm².