Optimization of Nd1+xBa2-xCu3O7 thin-film growth conditions using micro-Raman spectroscopy

Abstract

We explore optimal growth conditions for superconducting Nd 1+xBa2-xCu3O7 (NdBCO) thin films deposited under various oxygen pressures in the range of 100-800 mTorr. In this study we address spatial inhomogeneity, growth orientation, impurity phases, cation disorder, and oxygen deficiency of NdBCO thin films by using micro-Raman scattering. The films grown in the low oxygen pressure range of 100-200 mTorr show predominantly a-axis orientation and degraded superconducting properties with a critical temperature (Tc) of ∼80 K. The degradation of the transition temperature of the films deposited at lower oxygen pressure is attributed to the cation disorder, on the basis of analysis of the apical oxygen Raman mode. On the other hand, the samples grown in the higher oxygen pressure range of 400-800 mTorr show strong c-axis orientation and much less cation disorder. These features correlate with their high values of Tc and Jc.