Deposition of large area YBa 2Cu 3O 7 − δ thin films by magnetron sputtering

Abstract

Large area deposition of high Tc-superconducting thin films is an important topic with regard to many applications. Taking the advantage of a multitarget magnetron sputtering system, especially designed for preparing film sizes up to two inches in diameter, a variety of different film compositions can be achieved. To avoid problems arising from the chemical instability of barium we use three inch targets of the intermetallic compounds BaCu and YCu, respectively. Sputtering gas is a mixture of argon and oxygen. During deposition substrate temperature is kept at 500 °C to 700 °C. As grown films show nonmetallic behaviour due to a low oxygen partial pressure during the sputtering process which is mandatory to get the desired film stochiometry. Film quality is improved fundamentally by a short high temperature post annealing in the deposition chamber without breaking the vacuum at a pressure of 1mbar to 10 mbar of oxygen in the temperature range of 800 °C to 900 °C. Our best films so far show metallic behaviour and critical temperatures ( R = 0) above 85K. The correlation of the process parameters during deposition as well as during post annealing with electrical, structural and optical properties of the films is discussed.