Search

High quality single-crystal magnesium diboride (MgB2) nanowires with lengths exceeding 10 μm were successfully synthesized by hybrid physical chemical vapor deposition. The magnetization and electrical transport properties of single-crystal MgB2 nanowires (NWs) were measured. The superconducting transition temperature of the NWs was 37 K, as confirmed by magnetization measurements. The disordered behavior of the nanowires was observed by four-terminal current–voltage characteristic measurements of an individual NW from T = 10 to 300 K. The temperature-dependent resistivity curves for seven NWs collapsed into a universal curve described by the variable range hopping model, showing intrinsic nonmetallic transport properties. This implies that the granular superconducting defect states are critical to the superconductivity of the individual MgB2 NWs. [ABSTRACT FROM AUTHOR]

Abstract: The experiment for preparing MgB2 thin films by electron beam (e-beam) annealing of Mg–B multilayer is reported. The annealing process lasts less than 1s, which effectively suppresses the volatility of Mg as well as the reaction of Mg and oxygen. The influence of annealing parameters on the film quality including exposure time, accelerating voltage and beam current is investigated. It is found that e-beam with lower accelerating voltage can acquire MgB2 film with smaller annealing energy density. Also, double e-beam scan annealing process helps to obtain more uniform MgB2 thin films than the single scan. This rapid annealing method synthesizes MgB2 thin films with critical temperature Tc of 35K and critical current density Jc at 15K of 7.6×106 Acm−2. [Copyright &y& Elsevier]

MgB 2 superconducting films, whose thicknesses range from 10 nm to 8 µm, have been fabricated on SiC substrates by hybrid physical–chemical vapor deposition (HPCVD) method. It is the first time that the T c and the J c of MgB 2 films are studied on such a large scale. It is found that with the increasing of thickness, T c elevates first and then keeps roughly stable except for some slight fluctuations, while J c (5 K, 0 T) experiences a sharp increase followed by a relatively slow fall. The maximum J c (5 K, 0 T) = 2.3 × 10 8 A cm −2 is obtained for 100 nm films, which is the experimental evidence for preparing high-quality MgB 2 films by HPCVD method. Thus, this work may provide guidance on choosing the suitable thickness for applications. Meanwhile, the films prepared by us cover ultrathin films, thin films and thick films, so the study on them will bring a comprehensive understanding of MgB 2 films. [ABSTRACT FROM AUTHOR]

Abstract: MgB2 thin films were prepared by ex-situ annealing of Mg/B multilayers. Different precursor, substrate and annealing condition were investigated. After annealed in a flow of Mg vapor with reducing hydrogen ambient for 1–4min, high quality 20nm-thick c-oriented MgB2 thin films with and critical current density J C =2×106 Acm−2 at 30K were obtained. The mean roughness of the 20nm-thick film was 2.68nm. [Copyright &y& Elsevier]

The article presents a study which demonstrates the magnesium diboride (MgB2) superconducting whiskers synthesized by hybrid physical-chemical vapor deposition (HPCVD). The HPCVD setups that were employed in this experiment were quartz chamber with induction heating and stainless steel chamber with resistivity heating. A scanning electron microscope was used to analyze the morphologies of the whiskers. It has observed an onset temperature of 39 K.