Magnetron sputtering of Superconducting Multilayer Nb3Sn Thin Film

chamber which is 280 mm high and 100 mm of the diameter, we use two planarbalanced magnetrons. The Sn magnetron should be mounted at the bottom of thechamber because of the lower melting point, and the Nb magnetron is mounted at thetop of the chamber as shown in Fig. 3.2.The sample holder is in the centre of the chamber and it is an aluminium diskconnected to a rotary feed through. In this way we can rotate the samples, and every180° rotation we expose the sample to Nb plasma before, and Sn plasma after. Thedistance between targets and samples is 70 mm and during the sputtering we useArgon as process gas whose pressure is about 10 -3 mbar. No substrate heating systemswere employed.Fig. 3.3 the UHV multilayer deposition chamber3.2 Deposition on sapphireThe multilayer can be deposited on the sapphire and the Nb sample. Because ofthe perfect flat of the sapphire surface, all the parameters of the thin film on thesapphire can be measured, such as T c , RRR, thickness and XRD. On the other side,only T c and RRR of the thin film on the Nb sample can be measured. So, we firstinvestigate the multilayer deposited on the sapphire.3.2.1 Deposition parameterSame with the deposition of Nb thin film on the sapphire, the main parameters ofthe deposition multilayer are including the sputtering current, the deposition time andthe proceeding pressure. In our experiment, we fix the proceeding pressure of 5*10 -3mbar and the Sn sputtering current of 0.15mA. The deposition time is also fixed. Todeposit the buffer layer and over layer, we use the Nb sputtering current of 0.8mA for42