Engineering the surface morphology of inkjet printed Ag by controlling solvent evaporation during plasma conversion of AgNO3 inks

In this paper, we show that the surface morphology of silver (Ag) structures prepared by plasma conversion of particle-free inks can be controlled by solvent evaporation effcts. A series of three ethylene-glycol-based solvents were used to systematically vary the vapor pressure of the ink. Following inkjet printing, films were converted by exposure to a low-pressure, low-temperature radio-frequency (RF) plasma. Scanning electron microscopy (SEM) and profilometry of the Ag films showed that the surface roughness and porosity depend on the vapor pressure of the ink solvent, with each increasing with decreasing vapor pressure. As a result of changes to the porosity, electrical resistivity increased as the solvent vapor pressure decreased. To demonstrate the utility of a printing technique for rough and porous metal films, we fabricated Ag-based hydrogen peroxide (H2O2) sensors using inks comprised of the three ethylene-glycol-based solvents. The sensitivity of these sensors was found to increase with the surface roughness and porosity, which in turn, was related to the vapor pressure of the solvent.