Adlayer growth vs spontaneous (near-) surface alloy formation: Zn growth on Au(111)

Abstract

As part of an extensive effort to explore the function of Au/ZnO catalysts in the synthesis of methanol from CO2 and H2, we have systematically investigated the temperature dependent growth, structure formation, and surface intermixing of Zn on the herringbone reconstructed Au(111) surface and the thermal stability of the resulting surfaces by scanning tunneling microscopy (STM) and x-ray photoelectron spectroscopy (XPS). After Zn deposition at low temperatures, at about 105 K (STM) or below (XPS), we observed nucleation and two-dimensional growth of Zn islands mainly at the elbow sites of the Au(111) herringbone reconstruction. This results in local perturbations of the reconstruction pattern of the Au(111) substrate, which can create additional nucleation sites. XPS data indicate that Zn dissolution into deeper layers is kinetically hindered under these conditions, while local exchange with the Au surface layer, in particular at the elbow sites during nucleation, cannot be excluded. Zn deposition at room temperature, in contrast, results in near-surface alloy formation with a strongly distorted pattern of the herringbone reconstruction and condensation of the Zn and exchanged Au adatoms at ascending steps, together with some loss of Zn into deeper layers. Upon annealing, Zn atoms diffuse to lower layers and eventually to the Au bulk, and the surface successively regains its original Au(111) herringbone structure, which is almost reached after 500 K annealing. Compared with previous reports on the growth of other metals on Au(111), Zn shows a rather high tendency for intermixing and near-surface alloy formation.

Adsorption of multiple NO molecules on Au10−and Au9Zn−planar clusters. A comparative DFT study

“…On the other hand, previous studies of metal atom deposition on the Au(111) surface have concluded that, compared with the growth of other metals on Au(111), Zn shows a rather high tendency for intermixing and near-surface alloy formation. 45 Note that the atomic radius of both Zn (2.01 Å) and Zn + (0.88 Å) 46 is smaller than that of Au (2.14 Å). 47 Table 1 shows calculated properties for pure Au 10 À and doped Au 9 Zn À clusters including the spin multiplicity (2S + 1), the Gibbs binding energy per particle, the average bond distances between external-external and external-central atoms (d ext-ext and d ext-cen , respectively), the HOMO-LUMO gap, and the vertical detachment energy (VDE).…”

“…On the other hand, previous studies of metal atom deposition on the Au(111) surface have concluded that, compared with the growth of other metals on Au(111), Zn shows a rather high tendency for intermixing and near-surface alloy formation. 45 Note that the atomic radius of both Zn (2.01 Å) and Zn + (0.88 Å) 46 is smaller than that of Au (2.14 Å). 47…”

Stability of Pd Islands on Ag(111) and Au(111)

“…A variety of metals deposited on Au(111) have been studied, including Co, 23 Cr, 24 Fe, 25 Mn, 26 Mo, 27 Ni, 28−31 Pd, 4,32−35 Pt, 36 Rh, 37,38 Sn, 39 Ti, 40 and Zn. 41,42 Of most relevance to the present study are the STM results on the nucleation and growth of Pd islands on Au(111) by Stephenson et al 33 and Casari et al 34 Although these studies focused on the nucleation of Pd islands at room temperature (RT), they did not report on the stability of Pd islands as a function of annealing temperature as we do here. Baber et al also studied Pd on Au(111) using STM, and they discovered that the herringbone structure of Au(111) provided the entry sites for the incorporation of Pd atoms into the Au lattice and that the extent of mixing of Pd atoms with the Au surface depended on temperature.…”

Initial Stages of Sodium Deposition onto Au(111) from [MPPip][TFSI]: An In‐Situ STM Study for Sodium‐Ion Battery Electrolytes

“…[22] Among the different single crystal surfaces of Au, the densely packed (111) orientation is the most investigated in fundamental studies of the initial stages of metal deposition. [17,18,[23][24][25] It has been reported that the deposition of lithium on Au(111) starts at underpotential shifts of more than 1 V, [23] where the first islands are deposited. [17,23] At underpotentials, subsequent layer growth covers two or more layers.…”

“…Gold single crystals are commonly used in in‐situ STM studies due to their (i) well‐defined surface structure, (ii) ease in preparation, and (iii) noble character in terms of their stability towards water and oxygen [22] . Among the different single crystal surfaces of Au, the densely packed (111) orientation is the most investigated in fundamental studies of the initial stages of metal deposition [17,18,23–25] . It has been reported that the deposition of lithium on Au(111) starts at underpotential shifts of more than 1 V, [23] where the first islands are deposited [17,23] .…”