Speaker
Description
The recent discovery of superconductivity in hole-doped infinite-layer nickelate thin films [1] has sparkled a renewed interest in the condensed matter community.
This is motivated by the possibility to add another puzzle piece to the understanding of unconventional superconductivity, a phenomenon that has not yet been observed in infinite-layer polycrystalline samples[2].
The strain state induced by the substrate is suspected to play a key role in stabilizing the phase of superconductivity.
Inspired by recent advances in the epitaxial lift-off of oxide films[3], our idea is to free our nickelate thin films from substrate-induced stresses.
In this context, here, we present our preliminary results on the use of epitaxial lift-off techniques to fabricate free-standing membranes of nickelate films with the final goal to perform a topotactic reduction process and study the transport properties.
By using a pulsed laser deposition technique assisted by high-energy reflection electron diffraction, we have epitaxially grown $\mathrm{(Nd,Sr)NiO_3}$-based heterostructures on a sacrificial layer of water-soluble $\mathrm{(Ca,Sr)_3Al_2O_6}$[4].
Those sacrificial layers are particularly adapted to study the effect of the strain on the stabilization of the infinite-layer phase, since by selecting an opportune Ca/Sr ratio, they can be grown on various substrates. This allow a better integrity of the released membranes while minimizing cracks formation.
We can create membranes as large as 5x5 mm$^2$ that can be also fully transferred on PET or PDMS supports. Structural analyses conducted via X-ray diffraction and atomic force microscopy confirm the preservation of the crystalline quality of the membranes, close to that of the seed films.
References:
[1] Li, D. et al. Superconductivity in an infinite-layer nickelate. Nature 572, 624–627 (2019).
[2] Li, Q. et al. Absence of superconductivity in bulk Nd1−xSrxNiO2. Commun. Mater. 1, 16 (2020).
[3] Pesquera, D., Fernández, A., Khestanova, E. & Martin, L. W. Freestanding complex-oxide membranes. J. Phys. Condens. Matter 34, 383001 (2022).
[4] Lu, D. et al. Synthesis of freestanding single-crystal perovskite films and heterostructures by etching of sacrificial water-soluble layers. Nat. Mater. 15, 1255–1260 (2016).
