Growing a LaAlO₃/SrTiO₃ heterostructure on Ca₂Nb₃O₁₀ nanosheets

The two-dimensional electron liquid which forms between the band insulators LaAlO₃ (LAO) and SrTiO₃ (STO) is a promising component for oxide electronics, but the requirement of using single crystal SrTiO₃ substrates for the growth limits its applications in terms of device fabrication. It is therefore important to find ways to deposit these materials on other substrates, preferably Si, or Si-based, in order to facilitate integration with existing technology. Interesting candidates are micron-sized nanosheets of Ca₂Nb₃O₁₀ which can be used as seed layers for perovskite materials on any substrate. We have used low-energy electron microscopy (LEEM) with in-situ pulsed laser deposition to study the subsequent growth of STO and LAO on such flakes which were deposited on Si. We can follow the morphology and crystallinity of the layers during growth, as well as fingerprint their electronic properties with angle resolved reflected electron spectroscopy. We find that STO layers, deposited on the nanosheets, can be made crystalline and flat; that LAO can be grown in a layer-by-layer fashion; and that the full heterostructure shows the signature of the formation of a conducting interface.