Noble Metal Adatoms Research Articles

Adsorption and solar light activity of noble metal adatoms (Au and Zn) on Fe(111) surface: a first-principles study.

Noble metals such as gold (Au), zinc (Zn), and iron (Fe) are highly significant in both fundamental and technological contexts owing to their applications in optoelectronics, optical coatings, transparent coatings, photodetectors, light-emitting devices, photovoltaics, nanotechnology, batteries, and thermal barrier coatings. This study presents a comprehensive investigation of the optoelectronic properties of Fe(111) and Au, Zn/Fe(111) materials using density functional theory (DFT) first-principles method with a focus on both materials' spin orientations. The optoelectronic properties were obtained employing the generalized gradient approximation (GGA) and the full-potential linearized augmented plane wave (FP-LAPW) approach, integrating the exchange-correlation function with the Hubbard potential U for improved accuracy. The arrangement of Fe(111) and Au, Zn/Fe(111) materials was found to lack an energy gap, indicating a metallic behavior in both the spin-up state and the spin-down state. The optical properties of Fe(111) and Au, Zn/Fe(111) materials, including their absorption coefficient, reflectivity, energy-loss function, refractive index, extinction coefficient, and optical conductivity, were thoroughly examined for both spin channels in the spectral region from 0.0 eV to 14 eV. The calculations revealed significant spin-dependent effects in the optical properties of the materials. Furthermore, this study explored the properties of the electronic bonding between several species in Fe(111) and Au, Zn/Fe(111) materials by examining the density distribution mapping of charge within the crystal symmetries.

A DFT study of the adsorption of noble metal adatoms (Pd, Pt, Ag, Au) on 2D tin disulfide monolayers: Potential towards nanoscale electronic devices

Abstract We examined the structural characteristics and electronic properties of various transition metals (Pd, Pt, Ag, and Au) adsorption on the SnS2 monolayers and elucidated their possibility for utilization in next generation electronic devices. Our obtained results confirmed the strong interactions between the different noble metal adatoms and the hollow site of SnS2 monolayers. Our calculated binding energies suggested that the noble metal adsorbed SnS2 monolayers are energetically stable. The electronic properties analysis demonstrated that the electronic charges were drastically distributed over the adsorbed noble metal adatoms. Moreover, among all noble metal adatoms, embedded Pd atom has the strongest interaction with SnS2 monolayers because of its higher binding energy. In contrast, the weakest interaction corresponds to the embedding of Au adatom on the surface. Our calculated results propose new routes for the design and the development of highly talented noble metal embedded SnS2 based 2D materials.

The Effects of Heteroatom Adsorption on the Electronic Properties of Phosphorene

A new 2D material, phosphorene, has several remarkable advantages; various superiorities make phosphorene a research hotspot. This paper provides comprehensive information about the structure and electronic and magnetic properties of phosphorene adsorbed with atoms, including alkali and alkaline-earth metal atoms, nonmetallic atoms, noble metal atoms, and transition-metal atoms. Phosphorene adsorbed with alkali and alkaline-earth metal atoms, such as Li and Na adatoms, becomes an n-type semiconductor, while phosphorene adsorbed with Be and Mg atoms becomes a p-type semiconductor. In view of nonmetallic adatoms (B, C, N, and O), the B adatom decorated phosphorene becomes metallic, the band gap of phosphorene adsorbed with C adatom decreases, and the phosphorene is p-type with N adatom, while the electronic property of O adatom adsorption case is affected slightly. Regarding noble metal adatoms adsorption condition, the Ag adatom makes phosphorene a n-type semiconductor, the Au adatom induces phosphorene to have a magnetism of 1 μB, and the electronic property of phosphorene is changed by adsorbing with Pt adatom. Among transition-metal adatoms, such as Fe, Ni, Co, Cu, and Zn adatoms, the band gap is reduced when Fe/Ni adatom adheres to the surface of phosphorene, The Co adsorbed phosphorene turns into a polar-gapless semiconductor and phosphorene is proved to be n-type with Cu adatom, but it is testified that the Zn atom is not suitable to adsorb on the phosphorene.

Structural, Electronic, and Magnetic Properties of Adatom Adsorptions on Black and Blue Phosphorene: A First-Principles Study

Using first-principles calculations, we investigate the adsorption characteristics of alkali, alkaline-earth, nonmetallic, transition, and noble metal adatoms on phosphorene. The adsorption-induced tunable electronic structures are comparatively studied on two representative structures of phosphorene, i.e., black and blue phosphorus (P) nanosheets. Both black and blue P sheets exhibit good adsorption capability to foreign atoms, on which the binding energies of adatoms are stronger than on the BN, SiC, MoS2, or graphene sheets. On the black P sheet, most adatoms prefer to adsorb on the hollow site, whereas for the blue P sheet, the favored adsorption sites are element-dependent. The majority of alkali, alkaline-earth, and transition-metal adatoms prefer the valley site, noble metal adatoms the hollow site, and nonmetallic adatoms the bridge and top sites instead. The semiconducting behaviors of phosphorene are modified by adatoms, which can cause p-type and n-type doping or induce midgap states into the P...

Enhanced Bonding between Noble Metal Adatoms and Graphene with Point Defects

The adhesion of Ag,Au,and Pt adatoms on pristine graphene and that containing point defects including N-substitution,B-substitution,and a single vacancy,as well as the interfacial properties of these systems,were investigated using density functional theory.The calculations show that Ag and Au cannot bind to pristine graphene.In contrast,B and N-doping increase the interaction between Ag,Au,or Pt metal adatoms and graphene,while a vacancy defect leads to the strong chemisorption of metal adatoms on graphene.Based on electronic structural analysis,N-doping strengthens the covalent bond between Au or Pt and carbon atoms,while B-doping leads to the formation of a chemical bond between Au or Ag and B.The vacancy defect acts as an anchoring site for metal adatoms and increases the bonding between metal adatoms and carbon atoms.Therefore,three types of point defect can effectively enhance the interaction between noble metal adatoms and graphene in the sequence:vacancy defectB-dopingN-doping.

Adatoms-Induced Local Bond Contraction, Quantum Trap Depression, and Charge Polarization at Pt and Rh Surfaces

The extremely high catalytic efficiency of undercoordinated noble metal adatoms is indeed fascinating, but its chemical and electronic origin remains yet puzzling. Incorporating the BOLS correlation theory [Sun, C. Q. Prog. Solid State Chem. 2007, 35, 1] into the high-resolution XPS measurements [Baraldi, A.; et al. New J. Phys. 2007, 9, 143; Bianchettin, L.; et al. J. Chem. Phys. 2008, 128, 114706] has affirmed the BOLS expectations that the broken bonds induce local strain and quantum trapping in addition to polarization of the otherwise conductive half-filled s-shell charge by the tightly- and densely-trapped inner electrons of the adatoms. Both the trapped and polarized states would be detectable from the density-of-states evolution of the valence and the core bands. The trapped states have been discovered at the bottom edges of Pt(5d106s0) 4f7/2 and Rh 3d5/2 bands, and the polarized states only present at the upper edge of Rh(4d85s1) 3d5/2. It is suggested that the quantum trapping increases the electroaffinity and the polarization does oppositely. Therefore, the Rh adatom serves as a donor and the Pt adatom as an acceptor in the process of catalytic reaction.

Surface-state electrical conduction on the [formula omitted] surface with noble-metal adatoms

The Si(111)- 21 × 21 - (Ag+Cu) superstructure was found to be induced by adsorption of about 0.14 monolayers (ML) of copper atoms on the Si(111)- 3 × 3 - Ag surface at room temperature (RT), which was quite similar to the cases of the 21 × 21 superstructures induced by gold adsorption at RT and by silver adsorption at low temperature on the 3 × 3 - Ag surface. Photoemission spectroscopies showed that the high electrical conductance observed for this copper-induced superstructure was due to a two-dimensional intrinsic dispersive surface-state band crossing the Fermi level, not due to the surface space-charge layer, which is again similar to the gold-induced 21 × 21 surface. Each noble-metal adatom (gold, silver, copper) of less than ca. 0.1 ML coverage on the 3 × 3 - Ag surface was found to exist commonly as two-dimensional adatom gas (2DAG) phase before they turned into the 21 × 21 structure. The enhancement in surface conductance by the 2DAG phase was concluded to result from the donation of the adatoms' valence electrons into the surface-state band of the 3 × 3 - Ag substrate. The difference in stability of the 21 × 21 superstructures among gold-, silver- and copper-induced ones is discussed in terms of the first atomic ionization energy of the adatoms.

Interaction of Sulfur with Bimetallic Surfaces: Coadsorption of Sulfur and Noble Metals on Ru(001)

The coadsorption of S with Cu or Ag on Ru(001) has been investigated using TDS, XPS, XAES, and CO chemisorption. At 300 K, copper and silver atoms in contact with Ru(001) react with S[sub 2] to form noble-metal sulfides. The Cu-S and Ag-S bonds in these surface compounds break at high temperatures (> 800 K) producing sulfur and noble-metal adatoms that compete for the ruthenium electrons. This competition leads to a weakening of 5-6 kcal/mol in the strength of the Ru-Cu and Ru-Ag bonds. A sulfur adatom produces long-range perturbations on the surface, diminishing the ability for bimetallic bonding of several (5-10) adjacent ruthenium atoms. At [theta][sub s] = 0.2 ML (ML = monolayer), all the ruthenium sites show a strong weakening in their bonding interactions with copper or silver adatoms. Photoemission experiments examining the interaction of S[sub 2] with copper and silver multilayers at 300 K show the formation of thick films of Cu[sub 2]S and Ag[sub 2]S at a fast rate. The decomposition pathways for these films are similar: evolution of S[sub 2] into gas phase, with the noble metal remaining solid. For Ag[sub 2]S films the decomposition process starts around 800 K, whereas Cu[sub 2]S films aremore » stable up to 950 K. 55 refs., 13 figs.« less

The Importance of Indirect Interactions Between Adatoms for Temperature Dependent Processes on Metal Surface

The asymptotic form of the indirect pseudopotential interaction of noble metal adatoms on jelfium is used to interpret the phenomena arising during thermal treatment of the noble metal submonolayers on W(110). It is shown that the 2D condensation is an activated process. The growth of open clusters needs lower activation energy than the close-packed island formation. Therefore the open clusters should predominate at low temperatures and low coverages, as it is observed experimentally. On the basis of calculation of the total energy of submonolayers as a function of coverage Θ the experimental measurement of desorption energy vs. coverage is discussed.

Indirect interactions in clusters and submonolayers of noble metal adatoms on a jellium surface

The asymptotic form of the indirect pseudopotential interaction of noble metal adatoms is used to calculate the energy of clusters and submonolayers on a jellium surface. It is assumed that adatoms embedded into the nonuniform electron gas at the surface interact through the mean electron density which depends on the adatom-adatom and adatom-surface distances. The total energy of hexagonal submonolayers and surface clusters with linear, square and hexagonal structure is calculated. From the computations it follows that with increasing adatom concentration the growth of hexagonal close-packed islands is energetically more favourable than hexagonal or square submonolayers with regularly varying lattice constant.

Indirect interactions in clusters and submonolayers of noble metal adatoms on a jellium surface

Indirect interactions in clusters and submonolayers of noble metal adatoms on a jellium surface