Hybrid Physical Chemical Vapour Deposition (HPCVD) of Superconducting MgB2 Thin Films on three Dimensional Copper Substrates

Nilanjal Misra,Virendra Kumar,Reza Valizadeh

doi:10.5185/amlett.2020.111574

Abstract

The present work reports the design, development and application of a novel Hybrid Physical Chemical Vapour Deposition (HPCVD) technique for depositing MgB2 thin films, with potential superconductivity, directly on three dimensional (3D) surfaces. A novel solenoid magnetron based set up was used for depositing MgB2 thin films on 3D surfaces of Cu tube. Mg rod was used as the sputter target and source of Mg while high purity BBr3 was used as a novel boron precursor, which was injected into the system using Argon as carrier gas. The plasma mediated decomposition of BBr3 in presence of H2 gas was followed by chemical reaction between Mg and B atoms to deposit MgB2 film on the substrate. Samples were characterized by SEM, EDX, XRD and SQUID techniques. SEM-EDX confirmed deposition of a homogeneous, pore free and dense MgB2 film, while XRD analysis revealed the film to be polycrystalline and multiphasic rather than being purely c-axis oriented. Superconductivity analysis carried out using SQUID measurements indicated a sharp transition with Tc value of 39 K. From the M-H hysteresis loop, the lower critical field Hc1 and critical current density Jc at 4.2 K were calculated to be 700 Oe and 3.5 x 10 7 A/cm 2 , respectively.

Highlights

Since the discovery of superconductivity in binary metallic MgB2 in the year 2001 [1], a significant amount of work has been carried out to fabricate high quality thin films of this new material for fundamental studies and electronic device applications
One of its emerging applications is the development of superconducting radiofrequency (SRF) cavities for particle accelerators, made of bulk Copper coated with a layer of MgB2 thin film, as an attractive alternative to expensive bulk Niobium cavities [2,3,4]
We investigate the practicality and feasibility of using a novel modified HPCVD approach with indigenously developed HPCVD setup to directly deposit superconducting MgB2 film on 3D surfaces

Summary

Introduction

Since the discovery of superconductivity in binary metallic MgB2 in the year 2001 [1], a significant amount of work has been carried out to fabricate high quality thin films of this new material for fundamental studies and electronic device applications. One of its emerging applications is the development of superconducting radiofrequency (SRF) cavities for particle accelerators, made of bulk Copper coated with a layer of MgB2 thin film, as an attractive alternative to expensive bulk Niobium cavities [2,3,4]. The advantages of such MgB2 coatings include lower operating costs, improved thermal stability (due to the presence of Cu), low residual resistance, high transition temperature, as well as higher critical fields [2]. The third reason is that MgB2 has many properties that make it an attractive choice for superconducting applications, such as its suitability in fabricating good Josephson junctions, low anisotropy, fewer material complexities, fewer interface problems and a longer coherence length (ξ ~5 nm)

Methods

Results

Conclusion