c-axis charge dynamics in oxygen deficient (110) YBa2Cu3O7-δ films

Abstract In-plane c -axis aligned (1 1 0) YBa 2 Cu 3 O 7− δ thin films on (1 1 0) SrTiO 3 substrates have been successfully fabricated by pulsed laser deposition, using the self-template method. The oxygen deficiency of the films is controlled in situ by adjusting the annealing oxygen partial pressure P O 2 . Electronic transport and c -axis far-infrared reflectivity measurements have been conducted on these thin films. It is revealed that in the normal state the carriers are confined in the CuO planes and that their transport across the c -axis is incoherent. A pseudogap develops in the normal state at temperatures well above T c and it persists in the superconducting state. Upon decreasing the temperature below the critical transition temperature T c , coherence is built up for the carrier transport along the c -axis and a reflectivity edge associated with the Josephson plasma is observed.