Crystallinity of a-axis oriented YBa2Cu3O7−δ thin film epitaxially grown on NdGaO3 (110) by 95 MHz magnetron sputtering

Abstract

An a‐axis oriented 400 Å YBa₂Cu₃O_7−δ film has been epitaxially deposited on a NdGaO₃ (110) substrate by rf magnetron sputtering using a single YBa₂Cu₅O_x target. An excitation frequency of 94.92 MHz, seven times as high as the conventionally used 13.56 MHz, results in a lower self‐bias voltage which reduces degradation of films caused by resputtering due to negatively charged oxygen. Sharp streaks corresponding to the c‐axis lattice parameter of YBa₂Cu₃O_7−δ have been observed by reflection high‐energy electron diffraction, showing that the c‐axis is parallel to the surface of the NdGaO₃ substrate and the film surface is smooth on an atomic scale. The crystallinity has been characterized by Rutherford backscattering channeling analysis. A minimum yield, χ_min of 3.2%, has confirmed excellent crystallinity of the a‐axis oriented film.