The influence of La substitution and oxygen reduction in ambipolar La-doped YBa₂Cu₃O_ythin films

Abstract

We report hole and electron doping in Y 0.38 La 0.62 (Ba 2−x La x )Cu 3 O y thin films synthesized by the pulsed laser deposition technique and subsequently annealed in oxygen ambient or in a vacuum. X-ray diffraction studies suggested a single phase in p-type thin films and transport measurements showed a superconductor-to-insulator transition at x = 0.46. Hall measurements indicated electrons were successfully doped when the thin films were annealed in vacuum. The n-type samples demonstrated metallic behaviour within moderate temperature ranges, and a low in-plane resistivity (ρ ab ) and a high carrier density for 0.32 ≤ x ≤ 0.46. The increase in ρ ab for higher La doping levels, probably caused by charge compensation, is also discussed. The present result could be a significant step in searching for electron-doped superconductivity in the YBa 2 Cu 3 O y system.

Superconductivity in ultrathin films and nanoscale systems

“…Here a new emerging class of quantum phenomena of fundamental physics appear at the Bose-BCS crossover in multi-condensate superconductors [2]. Nanosize effects can now be manipulated by controlling defects in layered oxides [3]. A new approach is provided by controlling the self-organization of oxygen interstitials in layered copper oxides that show an intrinsic nanoscale phase separation [4].…”