Transfer Process of Epitaxial Functional Oxide Thin Films onto Flexible Substrates

Recently, fabrication of functional materials such as transparent conducting oxides on flexible polymer substrates has been intensively investigated. Because most flexible substrates are not heat resistive, these flexible devices have mainly consisted of amorphous oxides or organic materials showing excellent electric and optical transparency due to their low process temperature. We have proposed to realize flexible devices of functional oxides which show many attractive properties such as ferroelectricity, ferromagnetism. Thin film growth of functional oxides requires relatively high process temperature of several hundreds °C, thus it is difficult to deposit these materials on flexible substrates directly. We focused on acid etching of MgO (100) single-crystal substrates in order to realize flexibilization of epitaxial functional oxide thin films. In this study, we report a result on transfer of ferroelectric/piezoelectric BaTiO₃ (BTO) on flexible plastic sheet as a preliminary examination.
BTO thin films were deposited on MgO (100) substrate using pulsed laser deposition. After the deposition of BTO, the sample was soaked into a phosphoric acid solution. Using this process, we succeeded in transfer of c-axis oriented BTO thin film onto polymer sheet.