Effect of the thickness of SiO2 under layer on the initial stage of epitaxial growth process of yttria-stabilized zirconia (YSZ) thin film deposited on Si(001) substrate

Epitaxial growth of yttria-stabilized zirconia (YSZ) thin films on Si (001) substrates containing SiO2 layers of various thickness was in-situ monitor ed by reflection high-energy electron diffraction (RHEED). The inplane latt ice parameter of YSZ at the initial stage of the deposition (the thickness of YSZ was below 5 nm), was very close to that of the Si substrate when the thickness Of SiO2 was below 0.49 nm. The in-plane lattice parameter of YSZ was significantly decreased approaching that of bulk YSZ when the thicknes s of YSZ was over 5 nm. The relaxation of the lattice parameter was caused by the generation of misfit dislocations or regrowth of SiO2 between the Si and YSZ interface. On the contrary, if the thickness of SiO2 was between 0 .68 and 1.1 nm, the epitaxial growth was also confirmed, however, the in-pl ane lattice parameter did not change with the thickness of YSZ. The reason for the change of this lattice relaxation with the thickness of SiO2 was di scussed.