An investigation into the surface topology and thickness profile of functional ceramic spinel manganate sputtered, evaporated and screen-printed layers

In this paper an atomic force microscopy and scanning electron microscopy analysis of the surface grain structure of negative temperature coefficient of resistance (NTCR) thermistor nickel manganate layers produced by radio frequency (RF) magnetron sputtering, electron-beam evaporation and screen-printing is presented. Thin sputtered and evaporated films exhibited a dense low porosity surface with evidence for grain alignment in a brick layer fashion, whereas thick screen-printed layers displayed perceptible surface porosity. The layer thicknesses and the thickness distributions were analysed by surface profileometry. The three different deposition techniques used for film production are compared and described in detail, including the paste production for screen-printing, deposition conditions and post-deposition annealing and sintering processes for all three techniques. The effects of the differences in the film production processes on the film microstructure are discussed. This is important, because differences in microstructure can result in variations in the resistivity versus temperature characteristics.