Properties of Nb3Sn films fabricated by magnetron sputtering from a single target

Abstract

Superconducting Nb 3 Sn films were fabricated on sapphire and fine grain Nb substrates by magnetron sputtering from a single stoichiometric Nb 3 Sn target. The structural, morphological and superconducting properties of the films annealed for 24 h at temperatures of 800-1000 • C were investigated. The effect of the annealing time at 1000 • C was examined for 1, 12, and 24 h. The film properties were characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, energy dispersive X-ray spectroscopy, and Raman spectroscopy. The DC superconducting properties of the films were characterized by a four-point probe measurement down to cryogenic temperatures. The RF surface resistance of films was measured over a temperature range of 6-23 K using a 7.4 GHz sapphire-loaded Nb cavity. As-deposited Nb 3 Sn films on sapphire had a superconducting critical temperature of 17.21 K, which improved to 17.83 K when the film was annealed at 800 • C for 24 h. For the films annealed at 1000 • C, the surface Sn content was reduced to ~11.3% for an annealing time of 12 h and to ~4.1% for an annealing time of 24 h. The Raman spectra of the films confirmed the microstructural evolution after annealing. The RF superconducting critical temperature of the as-deposited Nb 3 Sn films on Nb was 16.02 K, which increased to 17.44 K when the film was annealed at 800 • C for 24 h.

Commissioning of a two-target DC cylindrical magnetron sputter coater for depositing Nb₃Sn film on Nb superconducting radiofrequency cavities

“…The two identical cylindrical magnetrons were made by Plasmionique Inc, Canada [42]. Each consists of 4 cylindrical magnets (neodymium N55 grade) coated with Ni, Cu, and epoxy and separated by spacers.…”

“…Methods used to fabricate Nb3Sn thin films include Sn vapor deposition [14][15][16][17], co-deposition of Nb and Sn by thermal evaporation [18], Nb dipping into Sn liquid followed by thermal diffusion [19], electrochemical synthesis [20,21], bronze routes [22,23], and magnetron sputtering [24][25][26][27][28][29][30][31]. The best RF results with Nb3Sn cavities have been achieved using vapor diffusion technique [13,15,32].…”

Fabrication of superconducting Nb3Sn film by Co-sputtering

“…Due to the close thermal expansion coefficient of Nb3Sn and Nb, the thermal stress on the Nb3Sn films fabricated on Nb substrates is low [5]. Therefore, there has been significant interest in the growth of Nb3Sn on Nb and the study of the Nb3Sn superconducting and microstructural properties [2][3][4][6][7][8][9][10][11]. Apart from the A15 Nb3Sn, Nb-Sn has other two phases; Nb6Sn5 with Tc < 2.8 K and NbSn2 with Tc < 2.68 K [12].…”

“…We have studied the deposition of Nb3Sn on Nb by sputtering from a single stoichiometric target and depositing multilayers on Nb and Sn followed by reacting them at high temperature [7][8][9][10]. The highest Tc of the films deposited from the stoichiometric target and multilayer sputtering was 17.44 with ΔTc = 0.03 K and 17.93 K with ΔTc = 0.03 K. The corresponding root-mean-square (RMS) surface roughness was 30 and 34 nm for the film deposited from the stoichiometric target and by multilayers, respectively.…”

Microstructural and Superconducting Radiofrequency Properties of Multilayer Sequentially Sputtered Nb3Sn films

“…Currently, Nb3Sn films are fabricated inside single cell and multicell cavities by Sn vapor diffusion [1,[4][5][6]. Magnetron sputtering is considered as a potential alternative to fabricate Nb3Sn SRF cavities [7][8][9][10].…”