Preparation of homo and hetero multilayer YSZ thin films by ultrasonic spray ICP flash evaporation method

High-density YSZ multilayer stacking thin films were synthesized by the ultrasonic spray ICP flash evaporation method. A mixed aqueous solution of zirconium nitrate and yttrium nitrate was atomized with an ultrasonic nebulizer and fed to thermal RF plasma to deposit YSZ thin films on silica glass substrates or (001) MgO single-crystal substrates. YSZ thin films on both substrates had (111) and (001) orientations normal to the substrates. YSZ thin films on the silica glass substrates were not oriented parallel to the surface of the substrates, whereas YSZ thin films on (001) MgO substrates were oriented parallel to the surface of the substrates. Their epitaxial relationships were (100) (001)YSZ//(001)MgO, [001][100]YSZ//[100]MgO and(111)YSZ//∼(001)MgO, [1̄1̄2]YSZ//∼[110]MgO. Thick multilayer stacking films were synthesized by 6 repetitions of cyclic deposition (repeated heating-deposition-cooling-cleaning procedures). In the multilayer stacking films the above orientational relationships were maintained. By applying the cyclic depoisition procedure, heterolayer stacking films could also be grown, in which the composition of the first layer was 3.1 mol%YSZ and that of the second layer was 11.1 mol%YSZ. The microstructure of the heterolayer-stacked dense film is almost the same as that of homolayer-stacked films. A distinct layer boundary, which is thought to result from the cyclic deposition method, or heterolayer stacking could not be observed by SEM, though peaks from each layer could be detected in the XRD analysis.