Influence of magnetron sputtering deposition conditions and thermal treatment on properties of platinum thin films for positive electrode–electrolyte–negative electrode structure

Abstract

In the present research, microstructure, porosity, stresses and resistivity of thin platinum electrodes (thickness of 200nm) deposited on titanium/silicon oxide/silicon and yttria stabilized zirconia (YSZ) substrates (the positive electrode–electrolyte–negative electrode (PEN) structure) were studied. Platinum films were formed at different working pressure of argon gas in the chamber during magnetron sputter-deposition process and following thermal treatment. Crystalline structure of the platinum (Pt) electrodes was analyzed using grazing incidence X-ray diffraction. Lattice parameter and residual stresses of the platinum thin films were defined using sin2ψ method. Morphology of electrodes was investigated using atomic force microscopy. Scanning electron microscopy was used to study surface morphology of the platinum thin films and microstructural properties of the PEN structure. Electrical properties of the platinum films were evaluated using the four-point probe method. Typical time intervals and substrate temperature ranges were defined to produce stable porous Pt electrodes that are applicable in the PEN structure (Pt-YSZ-Pt). It was found that lower Ar gas working pressure during magnetron sputtering results in denser and smoother platinum films. Correspondingly, higher Ar gas pressure allows the production of porous platinum thin films without any thermal treatment. Morphological changes of the Pt thin films were analyzed in the temperature region (500–800°C) that is typical of operation of micro solid oxide fuel cells.