Real-time spectroscopic ellipsometry of silver nanoparticle formation in poly(vinyl alcohol) thin films

Silver nanoparticle formation in poly(vinyl alcohol) thin films is analyzed in real time by spectroscopic ellipsometry. Modeling the data using the Maxwell-Garnett theory shows that the silver content predicted by the model depends of the film thickness. This is conjectured to be due to the absence of plasmon resonances in very small particles affecting the model. The size dependence of the free electron relaxation frequency is used to analyze the particle size during nucleation and growth. Evaporation of the polymer matrix is also monitored by real time ellipsometry and the plasmon resonance is observed to shift from 3.0 to 2.2 eV as the particles are liberated from the polymer. The particle density on the surface can be controlled by the silver concentration and the initial polymer thickness. The exposed particles are easily imaged with scanning electron microscopy, and the particle sizes are compared to the parameters predicted from the Maxwell-Garnett theory.