Electrical transport and Raman spectral studies of (110)-oriented PrBa_2 (Cu_(0.8)M_(0.2))_3O_7 (M = Ga, Al, Zn, Ni) thin films

摘要

The electrical transport and Raman spectral studies of (110)-oriented PrBa_2 (Cu_(0.8)M_(0.2))_3O_7 (M = Ga, Al, Ni, Zn) (PBCMO) thin films have been investigated. The electrical resistivity, ρ(T), of (110)-oriented PrBa_2 (Cu_(0.8)Ga_(0.2))_3O_7 (PBCGO) and PrBa_2 (Cu_(0.8)Al_(0.2))_3O_7 (PBCAO) thin films are many orders of magnitude higher than that of the (110)-oriented PrBa_2Cu_3O_7 (PBCO) thin films and follow Mott's 3D variable range hopping law up to room temperature. The electrical resistivity and Raman spectroscopic studies show that Al and Ga ions replace the Cu ions in the Cu-O chains of (110)-oriented PBCO and cause an extensive localization of charge carriers (holes) in the chains site of the PBCO. Our transport studies on YBa_2Cu_3O_7 (YBCO)/PBCGO and YBCO/PBCAO multilayers suggest that PBCAO and PBCGO thin films possess very less or no proximity effects. These results show (110)-oriented PBCGO and PBCAO thin films may serve as very effective insulators in YBCO based superconductor/insulator/superconductor tunneling Josephson junction.