Co and Phthalocyanine Overlayers on the Quantum-Well System Co(001)/Cu: Spin-Polarized Electron Reflection Experiments

Etienne Urbain,Wolfgang Weber,Martin Bowen,Samy Boukari,Eric Beaurepaire,Patrick Wetzel,Guillaume Garreau

doi:10.4236/jmp.2018.95060

Abstract

The influence of a Co or phthalocyanine (Pc) molecular overlayer on the properties of quantum-well resonances (QWR) in Cu layers atop Co(001) is studied by means of spin-polarized electron reflection. For Co atoms and Pc molecules, an energy shift of the QWR-induced signal is observed with increasing coverage and is attributed to a variation of the electron reflection phase at the Cu/Co and Cu/Pc interface. For Co we find a linear energy shift in the Cu QWR energy position with increasing coverage down to the sub-monolayer regime. This shows that the phase accumulation model remains accurate within the sub-monolayer regime of a discontinuous interface. An opposite sign in the energy shift between Co and Pc overlayers could reflect an opposite impact on the Cu surface work function of overlayer adsorption.

Highlights

Quantum confinement in thin metallic films gives rise to discrete quantum-well states that are known to lead, as the film thickness is varied, to variations in different physical quantities such as surface energy [2], thermal stability [3], work function [4], electrical conductivity [5] and surface adsorption [6] [7]
It has already been shown by Egger et al [28] that the very pronounced structures of Aex as a function of Cu thickness in the system Co(001)/Cu are directly related to the presence of quantum-well resonances (QWR) in the Cu film
We emphasize that the observed energy shifts of the QWR-induced structure is related to a phase shift

Summary

Introduction

Quantum confinement in thin metallic films gives rise to discrete quantum-well states (see Ref. [1] and references therein) that are known to lead, as the film thickness is varied, to variations in different physical quantities such as surface energy [2], thermal stability [3], work function [4], electrical conductivity [5] and surface adsorption [6] [7]. [1] and references therein) that are known to lead, as the film thickness is varied, to variations in different physical quantities such as surface energy [2], thermal stability [3], work function [4], electrical conductivity [5] and surface adsorption [6] [7]. This confinement can become spin-dependent if ferromagnetic layers are considered. Neither the intensities of the QWS (after consideration of the signal attenuation due to the CuPc layer) nor their energy positions change with increasing CuPc coverage

Objectives

Results

Conclusion