Experimental Control of the structure and discovery of emergent quasi-2D conductivity in SrCuO₂ ultra thin films
Ping-Chih Chiang1*, C.-S. Ku2, J.-C. Yang3, Y.-H. Chu4, J.-Y. Lin1
1Institute of Physics, National Chiao Tung University, Hsinchu, Taiwan
2National Synchrotron Radiation Research Center, Hsinchu, Taiwan
3Institute of Physics, National Cheng Kung University, Tainan, Taiwan
4Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan
* Presenter:Ping-Chih Chiang, email:pizejohn@yahoo.com.tw
Two-dimensional (2D) CuO₂ plane plays a key role in high-Tc superconductivity. A recent theoretical study predicted a transition from the chain-type structure to the bulk plane-type structure in SrCuO₂ films with thickness larger than five unit-cells (u.c.). In present study, by using pulsed laser-deposition technique SrCuO₂ ultrathin (1 - 20 u.c.) films were successfully grown on TiO₂ terminated SrTiO₃ substrates. The thickness-dependent structural transformation of the SrCuO₂ films were studied by synchrotron base x-ray diffraction, polarized X-ray absorption spectroscopy (XAS) at the Cu L edge as well as x-ray Laue nano diffraction. From synchrotron based x-ray diffraction and XAS measurements shown a bulk planar-type to a chain-type structure transformation upon reducing the thickness below 7 u.c. or 10 u.c. depending on the capping layer. Furthermore, the energy scan of X-ray Laue nano diffraction confirms that the chain-type SCO remained when the planar type SCO develop. The coexist of two phases shade a new light to design/fabricate single layer CuO₂, that can provide a new route to study the fundamental high Tc cuprates physics.

Keywords: SrCuO₂, monolayer copper oxide plane, structural transformation, superconductivity, oxygen sublattice