Pulsed Laser Deposition of Zr 1-x CexO 2 and Ce 1-x La x O 2-x/2 for Buffer Layers and Insulating Barrier in Oxide Heterostructures

Abstract

We have studied the pulsed laser deposition (PLD) of Zr1-xCexO2 and Ce1-xLaxO2-x/2 initially to grow buffer layers for perovskite films deposited on Si, LaAlO3, SrTiO3 and MgO and then to produce tunneling barriers for cuprate or manganite heterostructures. On (1 0 0) Si, the deposition of Zr1-xCexO2 (x = 0.12) produces a smooth epitaxial layer (R RMS = 0.25/1μm2), which allows the further deposition of high quality YBa2Cu3O7 (Tc ≥ 88 K) and La0.7Sr0.3MnO3 films. On the other hand, the use of Ce1-xLaxO2-x/2 (0≤ x ≤ 0.4) makes it possible to match the YBa2Cu3O7 and La0.7Sr0.3MnO3 layers to various substrates. The buffer layers are epitaxially grown with a 45° rotation of the in-plane axes with respect to those of the substrate, and the smoothness is high (R RMS = 0.25/1μm2). In the case of an ultra-thin barrier (≅2.5 nm) of Ce1-xLaxO2-x/2 sandwiched in a La0.7Sr0.3MnO3, the out-of-plane mismatch of 2 induces distortions at the interface steps, which propagate into the topmost La0.7Sr0.3MnO3 layer. This is in contrast to the case of SrTiO3 barriers where an ideal crystal continuity in the growth direction is observed.