YBa{sub}2Cu{sub}3O{Sub}(7-δ)-Ag sputtered thin films on MgO (100) and LaAlO{sub}3 (100) biased and unbiased substrates

摘要

In this investigation, we have deposited YBa{sub}2 Cu{sub}3 O{sub}(7-δ) -Ag thin films on various biased and unbiased substrates, including MgO (100), LaAlO{sub}3 (100) and Si (111), using a single stoichiometric composite target of YBa{sub}2 Cu{sub}3O{sub}(7-δ) with 10 wt.% Ag content, applying DC sputtering technique. The growth parameters are varied as following: sputtering gas pressure P{sub}(Ar)= 100 - 300 mtorr, sputtering power P = 30 - 80 W, substrate bias voltage V{sub}b= 0 - 220 V and film thickness t = 500 - 5000 A. M optimum bias voltage of V{sub}b=- 100 V was obtained under our experimental conditions. The post annealed (930°C for 1 hr in O{sub}2 environment) films exhibit superconducting state with T{sub}c (onset) of about 40 K for biased (on - axis), and 86 K for unbiased (off- axis) post annealed (800°C, 3 hr) films grown over both MgO(100) and LaAlO{sub}3(100) substrates. According to our SEM analysis, Ag particles are uniformly distributed in the annealed films with average grain size of about 0.3 μm located mostly at the grain boundaries. PIXE compositional analysis of the deposited films indicates deficiency of Cu and Ba for unannealed and Cu rich concentration for the annealed YBCO -Ag films grown over unbiased LaAlO{sub}3(100) substrate.