Atomic resolution of single-crystalline Y₂Ba₄Cu_6+nO_14+n (n=0, 1, 2) and laser-ablated thin film Y₁Ba₂Cu₃O₇ HT_cSC by STM

The scanning tunneling microscope (STM) is employed to investigate the submicron structure of the as-grown surface of single crystals of the high-temperature superconductors (HTcSC) series Y2Ba4Cu6+nO14+n (n=0,1, 2), abbreviated as 2-4-(6+n). In agreement with X-ray and neutron diffraction methods, we find unit-cell steps of 1.17 nm (2-4-6), 5.03 nm (2-4-7) and 2.73 nm (2-4-8) height. The surfaces of the (2-4-7) single crystals can be modified in such a way that fractions of the 5 nm unit cell height are observed. The surface of the crystals is atomically flat. To our knowledge, we report for the first time on atomic resolution on Y2Ba4Cu6+nO14+n (n=0,1,2) single crystals. In all three systems we find two approximately square atomic arrangements with lattice constants of 0.38 and 0.28 nm. A discussion of the species of the mapped atomic lattices will be presented. We also observe similar atomic lattices on laser-ablated thin films of Y1Ba2Cu3O7-δ. © 1992.