摘要
We have studied the proximityᵢnduced superconductivity in R7xR7R19.1o Ni nanoislands by combing scanning tunnelling microscopy_(s)pectroscopy (STM_(S)TS) with density functional theory (DFT) calculation. Through depositing Ni onto Pb(111) substrate at 80 K, the monolayer Ni nanoislands with the R7xR7R19.1o surface structure have been fabricated, where the termination of Ni atoms at hexagonal close packed (hcp) site is energetically preferred and the electron filling of 3d orbitals from the charge transfer leads to the vanishing magnetic moment of Ni atoms. The topographic R7xR7R19.1o lattice as well as the asymmetric height contrast in atomic unit cell are further corroborated by the STM simulations. With high spatial and energy resolution, tunneling conductance spectra have resolved an isotropic superconducting gap with Delta_(N)i₍R7xR7R19.1o)₁.29 meV, which is slightly larger than Delta_(P)b₁.25 meV. The temperature dependence of Delta_(N)i₍R7xR7R19.1o) supports the substrateᵢnduced superconducting proximity effect according to the same transition temperature Tc₇.14 K with the Pb(111). The line spectroscopy has spatially mapped out the small increase of Delta_(N)i₍R7xR7R19.1o), which could be explained by an enhanced electron_(p)honon interaction under the framework of Bardeen_(C)ooper_(S)chrieffer (BCS) theory as a manifestation of the hole doping of Pb(111) from the surface Ni atoms.