Superconductivity over 30 K of Nd2CuO4 Films on CaF2 Substrates

Abstract

Nd2CuO4 has a crystal structure called the Nd2CuO4 (T’) structure in which fluorite-like Nd2O2 slabs and CuO2 planes stack alternately. Nd2CuO4 is known to show superconductivity by carrier doping via anion/cation substitution, or making the oxygen sublattice highly ordered via a stringent control of thermodynamic conditions during crystal growth. In this study, CaF2 is used for growing Nd2CuO4 films, as a substrate material which contains fluorine atoms. The films show superconducting onset (Tonc) beyond 30 K. Furthermore, in contrast to reported superconductivity in this system, the emergence of superconductivity is found to be insensitive to post annealing procedures.