Pulsed laser deposition of oxide cuprate superlattices

Abstract

Pulsed laser deposition technique (PLD) has been successfully used to grow artificially layered films of the CuBa2(Ca1-xSrx)n-1 CunOy compound using only two targets having nominal composition BaCuOy and (Ca1-xSrx)CuOy respectively. n was varied between 2 and 5. The kinematic analysis of the x-ray diffraction spectra reveals that the average random discrete thickness fluctuations which affects both the BaCuOy and (Ca1-xSrx)CuOy layers are much smaller than one atomic layer. Such features are confirmed by the appearance of sharp peaks even for the nequals2 artificially layered structure where only one (Ca1-xSrx)CuOy cell is deposited in the stacking sequence. A major difference is found in the behavior of resistivity between films containing Sr and Ca respectively. Namely (BaCuO2)2/[(Ca1-xSrx)CuOy]n films never show any trace of superconductivity, while [BaCuO2]n/[CaCuO2]n films result to have, for growth oxygen pressures P > 0.2 mbar a full transition by laser deposition technique with a low interfacial disorder and give strong support to the idea of synthesizing new artificial high Tc structures by the PLD technique.