As-grown superconducting Mg-B films by single-target sputtering

Abstract

In this work, preparation of as-grown superconducting films has been attempted on Si (111) and Si-N substrates by rf-magnetron sputtering in the atmosphere of Ar using a single target. The target of 5 mm thick Mg disc of 50mm in diameter on which 5×5×1 mm3 B chips were put, was used. In order to vary the composition of films, the number of B chips was adjusted. The substrate temperature Td ranges from 230 to 250°C and the Ar pressure PAr is around 2.00 Pa. According to the measurement of resistivity, superconducting transition is seen in films deposited from the target with 12 to 18 B chips. The Tc of films appreciably depends on the number of B chips. The highest Tc of ~24K was seen in films deposited from the target with 14 B chips. In films from the target with 12 B chips, the Tc is markedly reduced to 13 K. With increasing the number of B chips from 14 to 18, the maximum Tc gradually decreases to 19K. X-ray photoemission spectroscopy analysis of some films reveals that the ratio of B/Mg increases with the number of B chips.