Pulsed laser deposition of oxide cuprate superlattices

Abstract

Pulsed laser deposition technique (PLD) has been successfully used to grow artificially layered films of the CuBa<SUB>2</SUB>(Ca<SUB>1-x</SUB>Sr<SUB>x</SUB>)<SUB>n-1</SUB> Cu<SUB>n</SUB>O<SUB>y</SUB> compound using only two targets having nominal composition BaCuO<SUB>y</SUB> and (Ca<SUB>1-x</SUB>Sr<SUB>x</SUB>)CuO<SUB>y</SUB> 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 (Ca<SUB>1-x</SUB>Sr<SUB>x</SUB>)CuO<SUB>y</SUB> 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 (Ca<SUB>1-x</SUB>Sr<SUB>x</SUB>)CuO<SUB>y</SUB> 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 (BaCuO<SUB>2</SUB>)<SUB>2</SUB>/[(Ca<SUB>1-x</SUB>Sr<SUB>x</SUB>)CuO<SUB>y</SUB>]<SUB>n</SUB> films never show any trace of superconductivity, while [BaCuO<SUB>2</SUB>]<SUB>n</SUB>/[CaCuO<SUB>2</SUB>]<SUB>n</SUB> films result to have, for growth oxygen pressures P &gt; 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.