Microstructures of CGO and YSZ thin films by pulsed laser deposition

Yttrium-stabilized zirconia (YSZ) and cerium gadolinium oxide (CGO) thin films were prepared by pulsed laser deposition (PLD) under different ambient pressures and substrate temperatures. The microstructures of the obtained films are compared with existing structural zone models for thin-film growth. The model developed by Thornton (1974) for metallic sputtered films is applied to the metal oxide films grown by PLD and gives a good description for the growth process and the dependence of the microstructure on deposition temperature and pressure. A map of formed microstructures is compiled as a function of background pressure and substrate temperature, and the conditions to obtain dense or porous films for YSZ and CGO are established. The two materials show the same dependence on temperature and pressure. Higher background pressure yields more porous films and a fully dense structure cannot be achieved for substrate temperatures in the range from room temperature to 800 degrees C. Of special interest for us was the realization and characterization of dense films processed at low temperature (< 500 degrees C) for the preparation of free-standing membranes to be used in a micro solid oxide fuel cell. We could achieve such films by processing at 400 degrees C in 0.026 mbar of oxygen. In-plane electric conductivities of the films were measured and correlated with the microstructures.