The optical characteristics of directly deposited gold nanoparticle (AuNP) films were investigated in the newly published work. Four samples were made using Ultrasonic Spray Pyrolysis technology, with AuNP deposition periods on the glass substrate of 15 minutes, 30 minutes, 1 hour, and 4 hours. The morphological characterisation of the formed films revealed that the earliest deposited AuNPs ranged in size from 10 to 30 nm, whereas bigger clusters of AuNPs evolved through coalescence and aggregation as the deposition process progressed. The produced layers were optically characterized using ultraviolet-visible spectroscopy (UV-vis) and ellipsometry. The ellipsometric measurements revealed a rising density and effective thickness of the AuNP layers. This feature allows for controlling the morphology and optical properties of deposited AuNPs on different substrates.
