Tuning the Morphological and Optical Properties of Pulsed Laser-Deposited Gold Nanoparticle Thin Films by Varying Number of Laser Pulses

The surface plasmon resonance (SPR) of metal nanoparticles (NPs) plays a crucial role in designing numerous chemical and biomolecule sensors. Therefore, in this work, gold (Au) NPs thin films were deposited on a glass substrate at the substrate temperature of 300°C using the pulsed laser deposition method. The effect of the number of laser pulses on the morphology and optical properties of Au NPs was investigated through scanning electron microscopy, ultraviolet-visible spectroscopy, and photoluminescence studies. Scanning electron microscopy revealed that the particle size increased from 14 to 28 nm whereas the inter-particle distance decreased from 19 to 8 nm with an increase of the number of laser pulses from 1000 to 5000, but the thickness of the Au NPs film increased from 107.5 to 132.4 nm. The observance of the SPR peak around 565–586 nm in absorption spectroscopy confirmed the formation of Au NPs. The red shift of the SPR peak position at higher numbers of laser pulses could be attributed to the simultaneous enhancement in the particle size and the reduction of the inter-particle distance. Further, the trend of the full-width half maxima in the intrinsic and extrinsic particle size region was studied, and the phenomena behind the SPR broadening was briefly explained. The photoluminescence spectrum has also shown a strong emission band at 530 nm, with a corresponding energy band gap of 2.34 eV, and the band position was in good agreement with the SPR peak position. This study suggests that the SPR properties of Au NPs can be tuned by varying the number of laser pulses as it strongly affects the morphology of Au NPs.