Characterization of nanoscale clusters fabricated by pulsed laser irradiation of thin Au films

The characterization of Au nanoclusters (AuNCs) on indium-tin-oxide (ITO) substrates fabricated by nanosecond pulsed laser irradiations of thin Au films is reported. By several hundreds of pulsed laser irradiations of 2.5 × 107 W cm−2 and 5 × 107 W cm−2 intensity in 1 min, the nanoscale clusters are formed in an ultrafast melting, collecting, growing-up and solidification process of 5, 7.5 and 10 nm Au films. The mean diameter and size distribution of nanoclusters are quantified by the statistical analysis on scanning electron microscopy (SEM) images. The melt dynamics and temperature changes of Au film under pulsed laser irradiation are obtained by quantitative evaluation. The extinction spectra of the initial Au films and formed Au nanoclusters on the ITO surface have also been measured. It has been found that the mean diameter, the surface density and extinction spectra of the induced AuNCs are influenced by the thickness of Au films and the laser intensity. The evolutional mechanism of the nanoscale clusters formation is discussed by the comparison on the morphology of the Au films with and without laser irradiations.