Morphology and N₂ Permeance of Sputtered Pd-Ag Ultra-Thin Film Membranes

The influence of the temperature during the growth of Pd-Ag films by PVD magnetron sputtering onto polished silicon wafers was studied in order to avoid the effect of the support roughness on the layer growth. The surfaces of the Pd-Ag membrane films were analyzed by atomic force microscopy (AFM), and the results indicate an increase of the grain size from 120 to 250-270 nm and film surface roughness from 4-5 to 10-12 nm when increasing the temperature from around 360-510 K. After selecting the conditions for obtaining the smallest grain size onto silicon wafer, thin Pd-Ag (0.5-2-µm thick) films were deposited onto different types of porous supports to study the influence of the porous support, layer thickness and target power on the selective layer microstructure and membrane properties. The Pd-Ag layers deposited onto ZrO₂ 3-nm top layer supports (smallest pore size among all tested) present high N₂ permeance in the order of 10(-6) mol·m(-2)·s(-1)·Pa(-1) at room temperature.