This work developed a technique for fabricating flexible epitaxial thin films of anatase-type Nb:TiO2 (epitaxial TNO) via a transfer process. In our prior work, epitaxial TNO deposited on LaAlO3 (001) single crystal substrates was lifted off and affixed to flexible polymeric sheets. However, many cracks occurred on the surfaces of the transferred thin films, such that the conductivity of the epitaxial TNO was drastically decreased. This loss of conductivity was attributed to the interruption of current paths by the cracks. These numerous cracks were linear and in most cases were oriented either parallel to the [100]anatase∥[100]LAO direction or parallel to the [010]anatase∥[010]LAO direction (where the subscripts anatase and LAO represent the materials for each Miller index). Therefore, cracking likely occurred as a consequence of the relaxation of epitaxial strain and a return to the original axial lengths of the TNO during the transfer process. In the present work, the surface of epitaxial TNO was coated with the ductile polymer SU-8 3050 as a relaxation absorber prior to the transfer. This modified transfer process greatly reduced crack formation in the TNO such that the conductivity of the thin film was improved by two orders of magnitude. Thus, pre-coating with a ductile relaxation absorber was shown to effectively suppress the cracking of flexible epitaxial TNO.
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