Epitaxial Ultrathin MgB2 Films on C-Terminated 6H-SiC( }\bar}}) Substrates Grown by HPCVD

• Published in: IEEE transactions on applied superconductivity 2023-08, Vol.33 (5), p.1-4
• Main Authors: Yang, Weibing, Chen, Ke, Kasaei, Leila, Feldman, Leonard C., Cunnane, Daniel, Karasik, Boris S., Xi, Xiaoxing
• Format: Article
• Language: English
• Subjects: <named-content xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" content-type="math" xlink:type="simple"> <inline-formula> <tex-math notation="LaTeX"> MgB_2</tex-math> </inline-formula> </named-content>; Chemical vapor deposition; Critical current density; Epitaxial growth; Hybrid Physical-Chemical Vapor Deposition (HPCVD); Magnesium compounds; Physical vapor deposition; Quantum phenomena; Resistance; Scanning transmission electron microscopy; SiC; Silicon carbide; Silicon substrates; Substrates; Superconducting films; Superconductivity; Surface morphology; surface termination; Thick films; Thickness; Transition temperature; ultrathin films
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2023.3235653

Ultrathin superconducting MgB 2 films are desirable for device applications and for exploration of new quantum phenomena in reduced dimensions. We have reported recently that smooth ultrathin MgB 2 films can be grown on carbon-terminated SiC substrates using Hybrid Physical-Chemical Vapor Deposition (HPCVD). In this work, we present a thickness dependence study of HPCVD-grown ultrathin MgB 2 films on C-terminated SiC with a focus on the thinnest superconducting films. The thickness of a nominally 2 nm thick MgB 2 film, controlled by deposition time based on thickness calibration data from thicker films, was confirmed by cross-sectional imaging via scanning transmission electron microscopy. We obtained a superconducting transition temperature T c = 27.2 K, a self-field critical current density J c (3K, 0T) = 2 × 10 7 A/cm 2 , and a normal-state sheet resistance near the transition R s = 44.5 Ω/sq in a 2 nm thick MgB 2 film while its root-mean-square roughness was 0.62 nm. These characteristics make the HPCVD-grown ultrathin MgB 2 films highly attractive for superconducting electronic applications.