Atomic visualization of copper oxide structure in the infinite-layer cuprate SrCuO2

Abstract

We report the atomic-scale structure of epitaxial films of parent infinite-layer compound SrCuO2 prepared on SrTiO3 by molecular beam epitaxy. In-situ scanning tunneling microscopy study reveals a stoichiometric copper oxide (CuO2)-terminated surface featured by 2  2 reconstruction, caused primarily by structural distortions of four adjacent CuO2 plaquettes. Furthermore, the subsurface Sr atoms have been rarely discernible, showing intra-unit-cell rotational symmetry breaking. These observations can be reasonably modelled by a periodic up-down buckling of oxygen ions on the CuO2 plane. Further post-annealing leads to the removal of surface oxygens and an incommensurate stripe phase. Our study provides indispensable structural information to help understand the exotic properties of cuprate superconductors.

Atomically Thin Superconductors

“…Ultra‐thin epitaxial films of the SrCuO 2 IL compound were grown on SrTiO 3 substrates by MBE in a layer‐by‐layer manner, whose atomic‐scale structure was systematically studied with in‐situ STM. [ 58 ] A key preparation step is to generate TiO 2 ‐terminated SrTiO 3 by annealing at 1200 °C before thin film deposition. The schematic diagram of SrCuO 2 films on TiO 2 ‐terminated SrTiO 3 is shown in Figure a.…”

Investigation of β‐Ga2O3 Film Growth Mechanism on c‐Plane Sapphire Substrate by Ozone Molecular Beam Epitaxy

“…[ 19,20 ] As an alternative oxygen source, ozone is a strong oxidizer and has been successfully used in the growth of superconductor films. [ 21,22 ] In ozone MBE, the effective ozone concentration at the substrate surface can be varied over a range of 40 times in magnitude by changing the ozone gas flow rate and pipe distance. [ 23 ] Sasaki et al also employed an ozone MBE system to grow homoepitaxial β‐Ga 2 O 3 films and studied the effect of substrate orientation on the growth rate.…”

Direct Visualization of Ambipolar Mott Transition in Cuprate CuO2 Planes

“…We report such measurement by choosing an infinite-layer SrCuO2 compound, because, besides its simplest crystal structure among cuprates (see Fig. 1A, inset), its surface is terminated with the CuO2 plane (13)(14)(15). Given the metastability of bulk infinite-layer cuprates, an ozone-assisted molecular beam epitaxy technique is utilized to prepare single-crystalline films of Sr1-xLaxCuO2+y (SLCO) and Sr0.92Nd0.08CuO2 (SNCO) with well-controlled dopant type and concentration (16).…”