Epitaxial growth of superlattice YbGaO3(ZnO)5 and InGaO3(ZnO)5 films by the combination of sputtering and reactive solid phase epitaxy

This article describes the epitaxial growth of superlattice YbGaO3(ZnO)5 (YGZO) and InGaO3(ZnO)5 (IGZO) thin films, which feature nanoscale multilayered structures, on (111) plane yttria-stabilized zirconia (YSZ) substrates through a combination of sputtering and reactive solid phase epitaxy processes. Our fabrication process involved thin ZnO epilayers deposited through sputtering onto the YSZ substrates, and then YbGaO3(ZnO)5 or InGaO3(ZnO)5 thin films deposited at room temperature on ZnO epi-layers, followed by high-temperature annealing (1200 °C) of the bilayer structures. To suppress vaporization of ZnO from the films, high-temperature annealing was performed in a box made of ceramic ZnO. We used X-ray diffraction and transmission electron microscopy (TEM) to analyze the thin films annealed under various conditions. The microstructural evolution in the film formed during reactive solid phase epitaxy process was explored by TEM observations. Single-crystalline YGZO and IGZO thin films without varying composition could be synthesized through a suitable annealing process in the ceramic ZnO box.