Research On The Growth And Properties Of MgB₂ Thin Films Fabricated On Different Substrates Via Hybrid Physical-chemical Vapor Deposition

The superconductivity of MgB2 was discovered in 2001, MgB2 has a high transition temperature over 39K, which is near the limit of BCS superconductors.Due to its low cost of raw materials, simple structure, absence of weak link between grain boundaries, a long coherence length(5nm), high transition temperature, high critical current density, high upper critical field, MgB2 has extensive application prospect in superconducting magnet and devices of superconductive electronics.The structure, the superconductivity, the fabrications and the applications of Mg32 are introduced in this thesis. And the main content of this thesis is the research on MgB2 thin films and ultra-thin films on SiC and MgO substrates fabricated by HPCVD. Introduce the influence factors on the quality and rate of the deposition of the MgB2 thin films, through the research of the MgB2 thin films on SiC and MgO substrates fabricated by HPCVD, then present the corresponding improving methods. By the research of the process of the preparation in detail and the superconductivity of the MgB2 ultra-thin films on SiC substrates fabricated by HPCVD, we know that the growth of he MgB2 ultra-thin films on SiC substrates follows the Volmer-Weber mode and for c-axis epitaxial. As the thickness of the ultra-thin films increases, the uniformity and connectivity improve gradually, critical transition temperature also increases and the residual resistivity decreases. The 20 nm ultra-thin film shows excellent performance at all aspects and an extremely high critical current density Jc (0 T, 5 K)≈0.82 × 107 A/cm2, which is enough for practical application of devices of superconductive electronics and is important for the applications of MgB2 in this fields.In addition, this thesis summarizes the characters of the MgB2 thin films fabricated by HPCVD and the direction of next work.