摘要
We have studied the proximity-induced superconductivity in (7×7)R19.1o Ni nanoislands by combing scanning tunneling microscopy/spectroscopy (STM/STS) with density-functional theory calculation. Through depositing Ni onto Pb(111) substrate at 80 K, the monolayer Ni nanoislands with the (7×7)R19.1o surface structure have been fabricated, where the termination of Ni atoms at the hexagonal close-packed site is energetically preferred and the filling of 3d orbitals from the charge transfer leads to the vanishing magnetic moment of Ni atoms. The topographic (7×7)R19.1o lattice as well as the asymmetric height contrast in atomic unit cell have been further corroborated by the STM simulations. With high spatial and energy resolution, tunneling conductance (dI/dU) spectra have resolved an isotropic superconducting gap with ?Ni(7×7)˜1.29 meV, which is slightly larger than ?Pb˜1.25 meV. The temperature dependence of ?Ni(7×7) supports the substrate-induced superconducting proximity effect according to the same transition temperature Tc˜7.14 K with the Pb(111). The line spectroscopy has spatially mapped out the small increase of ?Ni(7×7), which could be explained by an enhanced electron-phonon interaction (Vep) under the framework of Bardeen-Cooper-Schrieffer theory as a manifestation of the hole doping of Pb(111) from the surface Ni atoms.