Effect of Y-substitution on the electrical properties of epitaxial Bi2Sr2Ca1-xYxCu2O8+delta thin films

We have performed a study on the preparation conditions and electrical tran sport properties of epitaxial Bi2Sr2Ca1-xYxCu2O8+delta thin films. The depo sition of the Alms was carried out "in situ" by a high oxygen pressure de-s puttering technique on (100) SrTiO3 substrates. nle structural properties w ere determined by x-ray diffraction. By increasing the yttrium content the temperature dependence of resistivity change from a metallic to an insulati ng behavior. For x<0.50, the samples showed a metalic behavior in the norma l state and the transition temperature decrease with increasing yttrium con centration. Superconductor transition Width <Delta>T-C and d rho (n)/dT as function of the x value has been analized. For x greater than or equal to0. 50, the samples showed a semiconductor behavior what correspond to a variab le-range-hopping conduction between localized states in according to a two- dimensional system given by sigma = sigma . exp (- tau./tau)(1/3) Ultra-thi n Bi2Sr2Ca1-xYxCu2O8+delta films (for x-l) have been used as artficial barr iers in tunneling heterostructures with Bi2Sr2CaCu2O8+delta superconducting electrodes.