Characterization of reordered (001) Au surfaces by positive−ion−channeling spectroscopy, LEED, and AES

Abstract

An extensive investigation of the atomic arrangement on the (001) Au surface has been performed using the techniques of positive−ion−channeling spectroscopy (PICS), LEED, and AES. Both the normal surface in which the Au atoms are ordered in a square array and the reordered surface where it is proposed that the topmost layer of Au atoms are ordered in a hexagonal array have been examined. LEED and AES have been used in determining that the normal atomic arrangement producing the (1×1) LEED pattern is observed only when contamination is present, while the reordered surface producing the complex (5×20) LEED pattern is observed on surfaces which are atomically clean. The yield and energy distributions of 1 MeV 4He+ ions scattered from the oriented Au crystals have been used to determine the number of effective monolayers constituting the normal and reordered surfaces. Single alignment surface peaks and minimum yields have been determined, and experimental data are compared with predictions made by computer simulation calculations. It is found that the surface peak from the reordered surface is larger by an amount corresponding to ? 1 monolayer; this implies that only one extra hexagonal layer of atoms exists on the clean surface.

First-Principles-Based Force Field for the Interaction of Proteins with Au(100)(5 × 1): An Extension of GolP-CHARMM

“…Although no FF currently available can credibly describe the influence of AuNP edges and vertices on peptide adsorption, the relative length scales of the peptide sequences ,− and AuNPs currently used in experimental work ,, suggest that AuNP facets can often be acceptably approximated by planar surfaces . The reconstructed status of AuNP facets under experimental aqueous conditions is at present unknown. ,− However, the extended GolP-CHARMM FF could be used as an indirect probe of the reconstructed state of the surface. In addition, our new FF would enable peptide sequences, able to discriminate between the planar Au(100)(1 × 1) and Au(100)(5 × 1) surfaces, to be designed in a manner analogous to the experimental procedure used by Chui et al Simulations employing GolP-CHARMM, describing the two crystallographic planes of gold most commonly featured by AuNPs, Au(111) and Au(100), could be used as a first step to guide the rational design of peptide sequences able to control the size and/or shape of AuNP synthesis and assembly.…”

Self-Assembled Decanethiolate Monolayers on Au(001): Expanding the Family of Known Phases

“…Bulk-truncated Au(001) crystals have square symmetry. However, in order to lower its energy, the Au(001) surface reconstructs into the so-called “hex” phase with a 25% higher atomic density compared to the unreconstructed surface . Throughout the past decades, this reconstruction has gathered a lot of attention in spectroscopic and diffraction studies, − scanning tunneling miscroscopy (STM) and atomic force microscopy (AFM) studies, − and in theoretical reports, − to mention a few.…”

“…However, in order to lower its energy, the Au(001) surface reconstructs into the so-called “hex” phase with a 25% higher atomic density compared to the unreconstructed surface . Throughout the past decades, this reconstruction has gathered a lot of attention in spectroscopic and diffraction studies, − scanning tunneling miscroscopy (STM) and atomic force microscopy (AFM) studies, − and in theoretical reports, − to mention a few. Although there is a variety of reported unit cells, the accepted labeling formalism for the large hex unit cell is a (5 × N ) structure, where N ∼ 20.…”

Collective phenomena on metallic surfaces studied with scanning tunneling microscopy and low energy electron microscopy

“…In the inset, a larger-scale image is shown, revealing that a few hex stripes may remain on the surface, scale-bar: 20 nm. [52]. The hex reconstruction was initially designated as a (1×5) [51] cell, but soon a larger unit cell of (5×20) [52][53][54] was accepted.…”

“…[52]. The hex reconstruction was initially designated as a (1×5) [51] cell, but soon a larger unit cell of (5×20) [52][53][54] was accepted.…”