Effect of laser energy on optical properties of lead sulfide nanostructures

Abstract

This study investigates the influence of laser energy on the optical properties of lead sulfide (PbS) nanostructures deposited using the pulsed laser deposition (PLD) technique. Thin films were synthesized on glass substrates at room temperature using an Nd:YAG laser with varying energy levels (200, 300, 400, and 500 mJ). Structural analysis through X-ray diffraction (XRD) confirmed a polycrystalline cubic phase, while atomic force microscopy (AFM) revealed an increase in grain size with higher laser energy. Optical characterization showed that absorbance increases with laser energy, while transmittance decreases due to enhanced scattering and larger grain sizes. The absorption coefficient varied between 9×10⁴ cm⁻¹ and 42×10⁴ cm⁻¹, confirming direct allowed transitions. The optical bandgap ranged from 1.8 eV to 1.25 eV, decreasing with increasing laser energy, indicating changes in particle size and density. Furthermore, variations in the refractive index, extinction coefficient, and dielectric constants were analyzed, demonstrating a significant dependence on laser energy. These findings highlight the potential of tuning PbS thin film properties for applications in optoelectronics and photovoltaic devices.