Opportunities through high temperature treatments on transferred oxide membranes

New developments in the last half decade in epitaxial thin film growth have made it possible to separate the thin film from the substrate. In this membrane form, the single crystalline oxide can be transferred to any new platform or substrate of interest. This can be used to place it on substrates where it is difficult to grow them conventionally. Here we report our work on the transfer of complex oxide membranes on a pristine sapphire substrate, subjected to subsequent processing at temperatures >1000^oC. We observe that the membranes are inherently unstable at these high temperatures, owing to the large surface energy, and can agglomerate easily, as the membrane is not chemically bonded to the substrate. We show that the membrane self assembles into crystalline nanostructures upon thermal processing and at different temperatures goes through different stages of nanostructure evolution, which are consistent across a variety of thicknesses. We also show the quality of our nanostructures through transmission electron microscopy, which reveals a clean sharp interface between the transferred membrane and the sapphire substrate. With these results we can conclude that high temperature processing of oxide membranes on suitable substrates presents an opportunity for high quality oxide nanostructuring.