Dependence on the ablkated mass per pulse of morphology and optical properties of silver thin films

To know and to control experimental parameters that play a role in laser ablation is vital to define film prop- erties. Among the others, laser fluence is commonly used. Yet, when plasma expansion dynamics takes place through an ambient gas, the relation between the ablated mass per pulse and gas mass is critical and till now it was poorly in- vestigated. While the gas mass is fixed by the pressure in the deposition chamber, the ablated mass is not univocally de- termined by the laser fluence. For a given fluence value the ablated mass changes as a function of the irradiated target area. Here we show that nanostructured silver thin films de- posited keeping unaltered the laser fluence, while changing in a controlled way the irradiated area and hence the ab- lated mass per pulse, display markedly differentiated mor- phological and optical properties, as evidenced by electron microscopy and UV-Vis and Raman spectroscopies.