Magnetron sputtering of Superconducting Multilayer Nb3Sn Thin Film

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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
1 minute. The time of depositing multilayer is 10 minute. The rotation speed of thesample holder is about 13 second per circle. We only change the Nb sputtering currentform 1A to 1.8A. The parameters of each deposition are shown in Table 3.1. Where,ML means multilayer.Table 3.1 The parameters of multilayer deposition on sapphireRun s1 s2 s3 s4 s5Total Time(min) 12 12 12 12 12Nb voltage(V) 374 435 408 384 365buffer current(A) 0.8 0.8 0.8 0.8 0.8layer time(min) 1 1 1 1 1Nb voltage(V) 376 436 416 400 404Multilayercurrent(A) 1.0 1.2 1.4 1.6 1.8Sn Voltage(V) 520 400 480 540 512Current(A) 0.15 0.15 0.15 0.15 0.15time (min) 10 10 10 10 10Nb voltage(V) 367 400 380 369 355over current(A) 0.8 0.8 0.8 0.8 0.8layer time(min) 1 1 1 1 1Base pressure(mbar) 1.2*10 -8 1.5*10 -8 4.7*10 -8 2.3*10 -8 4.9*10 -8Ar Gas pressure(mbar) 5*10 -3 5*10 -3 5*10 -3 5*10 -3 5*10 -33.2.2 Vacuum annealingThe sample annealing is performed after the deposition for obtaining the A15 ofNb 3 Sn. The annealing should first heat the sample and thin film to about 1000°C.During that temperature, the Nb atom and Sn atom diffusion into each other, and thenthe A15 crystal structure is formed. According to the Fig.3.4, the heating temperatureshould be higher than 775°C, and the best is from 930°C to 950°C. The heating timeshould be longer than three hours, and then quench as quickly as possible. If thequenching time is shorter enough, the A15 crystal structure formed during the hightemperature is frozen. Otherwise, the A15 crystal structure will be broken at the lowtemperature.43
Page 1: UNIVERSITÀ DEGLISTUDI DI PADOVAFac
Page 7 and 8: IndexINDEX ........................
Page 9 and 10: IntroductionThe superconductor acce
Page 11 and 12: Fig. 1.1 Disc-loaded traveling-wave
Page 13 and 14: In Type-II superconductors, vortex
Page 15 and 16: needed for preventing the supercond
Page 17 and 18: The B1 crystal structure has a cubi
Page 19 and 20: NbN cavities literature, is often h
Page 21 and 22: superconducting magnet construction
Page 23 and 24: 775°C. From the same diagram, it i
Page 25 and 26: two types of electrons at the Fermi
Page 27 and 28: Of course, there are some other kin
Page 29 and 30: as shown in Fig.2.3. The four opera
Page 31 and 32: Fig.2.8 turbomolecular pumpFig. 2.9
Page 33 and 34: Fig. 2.14 The chamber covered with
Page 35 and 36: Fig. 2.17 the gasket and the magnet
Page 37 and 38: shown in Fig. 2.21 and Fig. 2.22. T
Page 39 and 40: Fig. 2.26 The interface of the surf
Page 41 and 42: Fig. 2.30 put the sample into the T
Page 43 and 44: Fig. 2.34 the performance of the th
Page 45 and 46: 1008038.5°{110}69.6°{211}sample1s
Page 47 and 48: 2dsinθ= nλ (2.3)Fig.2.44 the diff
Page 49: Chapter 3 Multilayer deposition of
Page 53 and 54: chamber 1 and is connected to the s
Page 55 and 56: 3.2.2.2 Analysis resultⅠ The thic
Page 57 and 58: In order to detect the component of
Page 59 and 60: measure the RRR. So the resistance
Page 61 and 62: 110100903480relative Intensity70605
Page 63 and 64: frequency of the cavity which is in
Page 65 and 66: Fig. 3.28 the inductor coilDuring t
Page 67 and 68: Fig. 3.32 fixing the sample with Nb
Page 69 and 70: second transition temperature is th
Page 71 and 72: source is the bulk Nb sample. Altho
Page 73 and 74: of 1A in the Fig. 3.37 and Fig. 3.4
Page 75 and 76: Table 3.10 the description of the p
Page 77 and 78: 1101001.0A10'-IND3 45 6 7 9 1011 12
Page 79 and 80: 1101009080341.8A10'INDrelative inte
Page 81 and 82: Reference1. A. Godeke, Nb3Sn FOR RA

Magnetron sputtering of Superconducting Multilayer Nb3Sn Thin Film

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