Papers by Author: Jun Wang

Abstract: Considerable progress to synthesize magnesium diboride (MgB₂) films by electron-beam annealing has been made. A series of MgB₂ films with a T_c higher than 35 K had been fabricated. MgB₂ film superconductivity is affected by electron-beam accelerating voltage, beam current, annealing duration, beam spot size and Mg/B ratio. In order to fabricate better MgB₂ films, these influence factors must be intensively studied. In this paper, the influence of e-beam current on superconductivity was investigated with an accelerating voltage of 32 kV, an annealing time of 0.26 s and different annealing beam currents of 9.9 mA, 10.7 mA, 12.8 mA, 13.3 mA and 14.0 mA. The results show the MgB₂ film with 12.8 mA has the highest T_c and the densest structure. Its zero-field J_c at 15K has reached 3.2×10⁶ A/cm². The variation of the film superconducting properties with the beam currents was grasped, which will lay the foundation for the fabrication of high quality MgB₂ thin films

Abstract: Birnessite MnO₂ nanosheets were synthesized by self-limiting deposition of KMnO₄ in a facile low-temperature hydrothermal process. The MnO₂ electrode exhibits a high specific capacitance of 169 F g^-1 at a current density of 0.1 A g^-1, good rate capability with a capacitance of 96 F g^-1 even at a high current density of 5 A g^-1, as well as excellent cycle stability with capacitance retention of 94% at 1 A g^-1 after 1,000 cycles.

Abstract: Zinc oxide (ZnO) and Zirconium (Zr) doped ZnO nano films have been successfully fabricated by radio frequency (RF) magnetic sputtering. The crystal structure and morphology were investigated by X-ray Diffraction (XRD), Field Emission-Scanning Electron Microscope (FE-SEM) and Transmission Electron Microscope (TEM). As the doped Zr content increases, ZnO nano films show various morphologies. The optical band gap of pure ZnO films increases from 3.27 eV to 3.53 eV with Zr concentration increasing to 9.66 at.%. After annealing, the polycrystalline structure of ZnO changes a little and the energy gap decreases. In addition, the clean and lower doped ZnO films show much lower transmittance.

Abstract: Ni-doped Cu3N films were prepared by radio frequency (RF) reactive magnetron sputtering method under different N2/(N2+Ar) ratios at room temperature. X-ray diffraction (XRD) patterns show that Ni-doped Cu3N films have the preferred growth along the (100) plane. The lattice parameters of Ni-doped Cu3N films increases obviously compared with the pure Cu3N films, which indicate that some Ni atoms are incorporated into the Cu3N host lattice. The electrical resistivity of Ni-doped Cu3N films has a remarkable change and decreases as the nitrogen ratio decreases. The optical energy gap of Ni-doped Cu3N film is around 1 eV which has no obvious change. The morphology and the thermal stability of doped Cu3N films were also studied.

Abstract: Zinc oxide (ZnO) and Dysprosium (Dy) doped ZnO nano films have been successfully prepared by radio frequency (RF) magnetron sputter. Then the crystal structure, morphology and optical of the films were investigated. All the samples have a preferred orientation with the (0 0 2) orientation perpendicular to the substrates. The surface morphology of the films changes greatly with the increasing of doping content. Agglomeration appears when the doping content is excess, which may result from the recrystallization of the small crystalline grain. The average transmittance in the visible range all exceeds 80% for the different doping content films and the band gap increases from 3.26eV to 3.34eV.