Studies of niobium thin film produced by energetic vacuum deposition

Abstract

An energetic vacuum deposition system has been used to study deposition energy effects on the properties of niobium thin films on copper and sapphire substrates. The absence of a working gas avoids the gaseous inclusions commonly seen with sputtering deposition. A biased substrate holder controls the deposition energy. Transition temperature and residual resistivity ratio of the niobium thin films at several deposition energies are obtained together with surface morphology and crystal orientation measurements by atomic force microscope inspection, X-ray diffraction analysis and transmitted electron microscope (TEM) analysis. The results show that niobium thin films on a sapphire substrate exhibit the best cryogenic properties at a deposition energy of around 123 eV. The TEM analysis revealed that epitaxial growth of film was evident when the deposition energy reached 163 eV for a sapphire substrate. Similarly, niobium thin films on copper substrates show that the film grows more oriented with higher deposition energy and the grain size reaches the scale of the film thickness at a deposition energy of around 153 eV. D

High-RRR thin-films of NB produced using energetic condensation from a coaxial, rotating vacuum ARC plasma (CEDTM)

“…2) Fresh, highly reactive Nb on the walls of the chamber acts like a getter reducing the background pressure. 3) Despite the low average deposition rate of ~ 0.1 nm/s , the instant deposition rate is 300 nm/s, much higher than other standard techniques [4][5][6][7][8] so impurities introduced during the discharge pulse are much lower, according to the expression [18]:…”

Equilibrium properties of superconducting niobium at high magnetic fields: A possible existence of a filamentary state in type-II superconductors

“…Those were two high-purity 5.7 µm thick films 4×6 mm 2 (Nb-F) and 2×4 mm 2 (Nb-F2), and two oneside polished 1 mm thick discs with diameter 7 mm (Nb-SC) and 19 mm (Nb-SC2) cut from the same single crystal rod. The film samples were cut from a film grown on sapphire using electron cyclotron resonance technique [16]; its residual resistivity ratio is 640. The GL parameter κ determined from magnetization curves in parallel field is 0.8 (1.3) near the critical temperature T c rising up to 1.1 (1.6) at 2 K for the Nb-F (Nb-SC) sample.…”

Deposition and Characterisation of Niobium Films for SRF Cavity Application

“…The working principle of inductive methods is as follows: screening currents are induced upon the sample surfaces by a low frequency field generated by a primary (excitation) coil, during the transition the screening currents change the voltage induced in a secondary (pickup) coil. In the single coil method the excitation coil acts as the secondary one tuned to the third harmonic of the primary frequency [23]. Examples of T c inductive measurements on UHVCA-coated Nb films are shown in figure 1.…”

“…In the early 2000's, besides new methods designed to improve the sputtering process, such as High Peak Power Pulsed Sputtering, conformal cathode and bias sputtering [18], there were proposed two alternative coating techniques: arc coating in ultra-high vacuum (UHVCA) [19][20][21] and Electron Cyclotron Resonance post-ionisation [22,23], in order to produce ultra-pure, more bulk-like Nb films. Their main features are the absence of the auxiliary gas needed for sputtering, and the absence in the plasma of atoms of the material to be deposited, since applied plasma is fully ionised.…”