Low temperature, pressure-assisted sintering of nanoparticulate silver films

The laser ablation of microparticle aerosol (LAMA) process was used to direct-write nanostructured, patterned films of silver with thicknesses in the range 20–200 μm at room temperature. A critical difference between the LAMA process and conventional processes for depositing patterned, thick films is that the LAMA process does not require surfactants that can interfere with post-deposition sintering. Thus, LAMA-produced films allow the intrinsic sintering of nanoparticulate films to be studied directly. Post-deposition sintering was conducted over a range of temperatures (100–175 °C) and compression loads (25–600 N) and the strength and electrical resistivity of the sintered samples were measured. The samples were characterized using optical microscopy, profilometry, SEM, and XRD and the density of the deposits were determined from the grain size, resistivity and known relationships between these parameters and density. LAMA-produced films were found to sinter to produce high strength, high conductivity films at temperatures 50–100 °C lower than conventional processes that use organic additives. Mechanisms for the low-temperature sintering of the nanostructured films are discussed and compared with established theory for pressure-assisted sintering.