Non-Hillock Formation and Population of Ag/TiO2 Nanoparticles through Stepwise Annealing

Magnetron sputtered Ag nanofilms were coated on TiO2 layers deposited on SiO2/Si substrates. The films were then post-annealed to a maximum temperature of 500 0C at different time and temperature intervals according to the chosen number of annealing steps to produce non-hillock dewetted Ag nanoparticles. The annealing steps ranged from one to four. The cumulative annealing time was fixed at 30 minutes. The changes of particle distribution, morphological and structural properties of the non-hillock dewetted particles with the number of annealing steps were investigated. Scanning electron microscope (SEM) and X-ray Diffraction (XRD) machine were employed for the films morphological and structural analysis respectively. The population of the dewetted particles increased with the increase in the number of annealing steps. However, the dewetted areas and particle sizes decreased with the increase in the number of annealing steps. Higher densities of dewetted particles on the nanoscale were only possible at higher numbers of annealing steps. The highest circularity of the dewetted particles was recorded by the sample that was annealed in two equal steps. There wasnt any significant difference among the particle crystal structures of films annealed at different steps. The XRD patterns were mainly from metallic Ag for films annealed at higher number of steps. The sample annealed in one step had XRD peaks from both Ag and TiO2.