Cl-functionalized scanning tunneling microscopy （STM） tips are fabricated by modifying a tungsten STM tip in situ on islands of ultrathin NaCI（100） films on Au（111） surfaces. The functionalized tips are used to ...Cl-functionalized scanning tunneling microscopy （STM） tips are fabricated by modifying a tungsten STM tip in situ on islands of ultrathin NaCI（100） films on Au（111） surfaces. The functionalized tips are used to achieve clear atomic- resolution imaging of NaCI（100） islands. In comparison with bare metal tips, the chemically modified tips yield drastically enhanced spatial resolution as well as contrast reversal in STM topographs, implying that Na atoms, rather than C1 atoms, are imaged as protrusions. STM simulations based on a Green＇s function formalism reveal that the experimentally observed contrast reversal in the STM topographs is due to the highly localized character of the Cl-pz states at the tip apex. An additional remarkable characteristic of the modified tips is that in dI/dV maps, a Na atom appears as a ring with a diameter that depends crucially on the tip-sample distance.展开更多
Mass-selected anionic cobalt clusters of two different sizes （Co2 and Co13） were deposited onto ultrathin NaC1 films grown on an Au（111） substrate. Using scanning tunneling microscopy experiments and density funct...Mass-selected anionic cobalt clusters of two different sizes （Co2 and Co13） were deposited onto ultrathin NaC1 films grown on an Au（111） substrate. Using scanning tunneling microscopy experiments and density functional theory simulations, we show that the deposited Co2 cluster dissociates and that the resulting Co atoms dope the NaCI surface by substituting Na ions. In contrast, the larger Co13 cluster does not dissociate and remains stable on top of the NaC1 film. The size- dependent fragmentation of clusters is an important aspect in the understanding of the chemical interaction between size-selected small aggregates of atoms and supporting surfaces.展开更多
文摘Cl-functionalized scanning tunneling microscopy （STM） tips are fabricated by modifying a tungsten STM tip in situ on islands of ultrathin NaCI（100） films on Au（111） surfaces. The functionalized tips are used to achieve clear atomic- resolution imaging of NaCI（100） islands. In comparison with bare metal tips, the chemically modified tips yield drastically enhanced spatial resolution as well as contrast reversal in STM topographs, implying that Na atoms, rather than C1 atoms, are imaged as protrusions. STM simulations based on a Green＇s function formalism reveal that the experimentally observed contrast reversal in the STM topographs is due to the highly localized character of the Cl-pz states at the tip apex. An additional remarkable characteristic of the modified tips is that in dI/dV maps, a Na atom appears as a ring with a diameter that depends crucially on the tip-sample distance.
文摘Mass-selected anionic cobalt clusters of two different sizes （Co2 and Co13） were deposited onto ultrathin NaC1 films grown on an Au（111） substrate. Using scanning tunneling microscopy experiments and density functional theory simulations, we show that the deposited Co2 cluster dissociates and that the resulting Co atoms dope the NaCI surface by substituting Na ions. In contrast, the larger Co13 cluster does not dissociate and remains stable on top of the NaC1 film. The size- dependent fragmentation of clusters is an important aspect in the understanding of the chemical interaction between size-selected small aggregates of atoms and supporting surfaces.
