Growth mechanism for epitaxial SrTiO₃ using remote epitaxy

Lattice mismatch between a crystalline film and substrate can lead to the formation of defects such as dislocations. Remote epitaxy is a promising approach to avoid this. The question of the growth mechanism is, however, still open. For instance, is the remote epitaxy assisted through the interatomic potential of the substrate via the graphene layer, or is it pin-hole-assisted growth? In this talk, we will present a detailed growth study using hybrid molecular beam epitaxy that employs a metal-organic precursor, titanium tetraisopropoxide (TTIP), to supply both Ti and oxygen (without the need for additional oxygen). This approach prevented the oxidation of the graphene layer while providing epitaxial SrTiO₃ films. Films were successfully exfoliated and transferred onto other substrates. Using Raman spectroscopy and high-resolution X-ray diffraction, we show that the transferred SrTiO₃ membrane is single-crystalline and that the graphene layer remained intact to the substrate after exfoliation. We will discuss how pinholes or wrinkles in graphene can influence the growth and surface morphology of the SrTiO₃ film, in addition to discussing the growth mechanism during remote epitaxy.