| Metal nanostructures have attracted considerable attention in recent years due to the potential applications in aspects of nanoscale electronics and atomic-scale storage devices as well as chemical catalysts and sensors. Inparticular, understanding the electronic, physical and chemical properties of metal clusters and monolayer became an issue attracting wide attention of a large number of researchers. Theoretical calculations focused on the geometry, stability, electronic and magnetic properties of Pd clusters and Pd monolayer adsorbed on the substrates with different properties (including NiAl(110), ZnO{0001}, MoS2monolayer) were carried out with in the framework of spin density functional theory (DFT).Fristly, theoretical calculations on the geometry, stability, electronic and magnetic properties of small palladium clusters Pdn(n=1-5) adsorbed on the NiAl(110) alloy surface has been carried out. In agreement with the experimental observations, both Ni-bridge and Al-bridge sites are preferential for the adsorption of single palladium atom. Among the possible structures considered for Pdn (n=1-5) clusters adsorbed on NiAl(110) surface, Pd atoms tend to form one-dimensional (1D) chain structure at low coverage (from Pd1to Pd3) and two-dimensional (2D) structures are more stable than three-dimensional (3D) structures for Pd4and Pd5. Furthermore, metal-substrate bonding prevails over metal-metal bonding for Pd cluster adsorbed on NiAl(110) surface. The density of states for Pd atoms of Pd/NiAl(110) system are strongly affected by their chemical environment, such as the modification of NiAl and the effect of surrounding Pd. The magnetic feature emerged upon the adsorption of Pd clusters on NiAl(110) surface was due to the charge transfer between Pd atoms and the substrate. These findings may shade light on the understanding of the growth of Pd metal clusters on alloy surface and the construction of nanoscale devices. In addition, the infinite Pd chains supported by NiAl(110) exist two configurations, the interactions among the increasing number of adatom resonance states enentually give rise to a band of resonance state, wihch is caused by substrate-mediated coupling and the direct5sp orbital overlap of adjacent Pd.Secondly, we have systemically studied the structural and electronic properties of Pd adsorbed on ZnO{0001} polar surface with different coverage, and analyzed the effect of interface of Pd/ZnO system. When the coverage increased to1ML, Pd atoms prefer to adsorb on fcc sites of ZnO{0001} surface; while Pd located at the top of O. After Pd adsorbed on ZnO(0001) surface, new band states emerged near the Fermi energy, and the electron density of Pd remain localized. Pd/ZnO (000-1) system is magnetic, which is caused by the hybridization between Pd and the O atom of substrate. Upon adsorption of Pd, the work function of system has change, which is caused by the change transfer between Pd and ZnO. The Schottky barrier height is0.65eV and1.16eV for Pd/ZnO(0001) and Pd/ZnO(000-1), respectively.Thridly, we have investigated firstly the structural, electronic and magnetic properties of Pdn (n=1-5) clusters adsorbed on MoS2monolayer. The initial growth of Pd clusters adopt Volmer-Weber mode, the Pd-Pd bonding is stronger than adsorbate-substrate bonds with the increasing of Pd coverage.The charge transfers from Pd clusters to substrate and the catalytic activity of Pd clusters with positive charge may be affected. Then the adsorption effects of the noble metal atoms (Ni, Pd, Pt, Cu, Ag, and Au) on electronic and magnetic properties of MoS2monolayer are investigated. To be comparaed, we present total energy calculations of the adsorption of Pd and Au monolayer on MoS2(0001) surface. We find that Au is suitable to be choosed as contact electrode for MoS2-based devices becaused of the stronger charge transfer between the Au adlayer and MoS2substrate.At last, we summarize the whole work and make an outlook to the effect of surface defects and reconstruction on the growth of metal clusters. |
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