Fabrication Of Superconducting Magnesium Diboride Thin Film By Chemical Vapor Deposition

Superconducting MgB2 thin films were fabricated on single-crystal sapphire substrate by HFCVD and HPCVD,respectively.The experiments were carried out both in situ and ex situ.In situ method refers to acquiring MgB2 thin films directly during the deposition process.Ex situ method is defined as obtaining MgB2 thin films indirectly by post-annealing of precursor B film in high Mg vapor pressure at high temperatures. The crystal structures of resultant films were characterized by X-ray diffraction (XRD) (-2( The surface morphology and chemical compostion of resultant films were analyzed by scanning electron microscopy(SEM) and X-ray energy dispersive spectroscopy(EDX),respectively.The superconducting critical transition temperatures of resultant films were measured by standard four-probe method and dc SQUID.The results indicates that superconducting MgB2 thin films can be prepared by HFCVD in a single-step with the maximum critical transition temperature Tc of 36K;the best critical transition temperature Tc of thin films grown by HPCVD in a single-step is 34K.The optimal zero resistance temperature Tco of thin films fabricated ex situ is 37 K by post-annealing of precursor B film at 800℃ for 1 h under high Mg vapor pressure.