Thickness-induced insufficient oxygen reduction inLa2−xCexCuO4 ± δ thin films

Abstract

A series of electron-doped cuprateLa2−xCexCuO4 ± δ thin films with different thicknesses have been fabricated and their annealing times areadjusted carefully to ensure the highest superconducting transition temperature. Thetransport measurements indicate that, with the increase of the film thickness (<100 nm), the residual resistivity increases and the Hall coefficient shifts in thenegative direction. Furthermore, the x-ray diffraction data reveal that thec-axis latticeconstant c0 increases with the decrease of film thickness. These abnormal phenomenacan be attributed to the insufficient oxygen reduction in the thinfilms. Considering the lattice mismatching in the ab plane between theSrTiO3 substrates and the films, the compressive stress from the substrates may be responsible forthe more difficult reduction of oxygen in the thin films.