Surface Investigation on Electrochemically Deposited Lead on Gold

Alicja Szczepanska,Natasa Vasiljevic,Neil Fox,Gary Wan,Mattia Cattelan

doi:10.3390/surfaces2010006

Alicja Szczepanska, Natasa Vasiljevic + Show 3 more

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https://doi.org/10.3390/surfaces2010006

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Journal: Surfaces	Publication Date: Jan 17, 2019
Citations: 4	License type: CC BY 4.0

Affiliation: University of Bristol

Abstract

Electrodeposition of Pb on Au has been of interest for the variety of surface phenomena such as the UnderPotential Deposition (UPD) and surface alloying. Here, we examined the interface between the electrodeposited Pb film on Au, using surface sensitive techniques such as X-ray Photoelectron Spectroscopy (XPS), Ultraviolet Photoelectron Spectroscopy (UPS), Energy-Filtered Photoemission Electron Microscopy (EF-PEEM) and Work Function (WF) mapping. The initially electrodeposited Pb overlayer (~4 ML equivalent thickness) was transferred from the electrochemical cell to the UHV system. The deposited Pb layer was subjected to Argon sputtering cycles to remove oxide formed due to air exposure and gradually thinned down to a monolayer level. Surface science acquisitions showed the existence of a mixed oxide/metallic Pb overlayer at the monolayer level that transformed to a metallic Pb upon high temperature annealing (380 °C for 1 h) and measured changes of the electronic interaction that can be explained by Pb/Au surface alloy formation. The results show the electronic interaction between metallic Pb and Au is different from the interaction of Au with the PbO and Pb/PbO mixed layer; the oxide interface is less strained so the surface stress driven mixing between Au is not favored. The work illustrates applications of highly surface sensitive methods in the characterization of the surface alloy systems that can be extended to other complex and ultrathin mixed-metallic systems (designed or spontaneously formed).

Highlights

Electrodeposition of Pb on Au is a well-known system characterized by Stranski-Krastanov growth [1]
The electrodeposition of Pb on Au starts by the formation of the epitaxial monolayer positive from the equilibrium potential for bulk deposition known as Underpotential Deposition (UPD), followed by the nucleation of 3D islands in the OverPotential Deposition (OPD) region [2,3]
An incommensurate, electrocompressed closely packed hexagonal structure of a complete Pb UPD ML has been analyzed by a range of techniques including Scanning Tunneling

Summary

Introduction

Electrodeposition of Pb on Au is a well-known system characterized by Stranski-Krastanov growth [1]. The electrodeposition of Pb on Au starts by the formation of the epitaxial monolayer positive from the equilibrium potential for bulk deposition known as Underpotential Deposition (UPD), followed by the nucleation of 3D islands in the OverPotential Deposition (OPD) region [2,3]. Microscopy (STM), Atomic Force Microscopy (AFM), ex situ Low Energy Electron Diffraction (LEED). In situ x-ray diffraction [8,12,13,14,15,16]. The UPD of Pb on Au has been used in a wide range of applications including measurements of surface area/roughness, surface structure characterization, chemical composition measurements, electrocatalysis, sensing as well as a mediation of the epitaxial thin film growth.

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