Inelastic Background Modelling Applied to Hard X-ray Photoelectron Spectroscopy of Deeply Buried Layers

Result of the Month

The HAXPES lab system at the Henry Royce Institute Hub in Manchester. Pictured is Suresh Maniyarasu, PhD student who holds an Overseas Research Studentship and Research Impact Scholarship at the University of Manchester, who is one of the team working on the HAXPES.

Overlayer thicknesses up to 200 nm are measured on the HAXPES-lab instrument, where inelastic background modelling (using the QUASES software, www.quases.com), obtaining the overlayer thickness within a 5% error. These spectra show how the inelastic background provides a “signature” for the depth distribution of the element. Also, it should be noted the Ir content in the complex is only 3 atomic %; HAXPES of larger elements provides a high sensitivity using deeper core levels.

A Comparison of Synchrotron and Lab-based (9.25 keV) Measurements

Author: Ben F. Spencer (ben.spencer@manchester.ac.uk) Institute: ''Department of Materials, The University of Manchester, Oxford Road, Manchester, United Kingdom '' Applied Surface Science
URL: https://doi.org/10.1016/j.apsusc.2020.148635
Date: 3/2021 Instruments: HAXPES Lab, EW4000

Personal Note of the Author 

We were delighted to obtain the world’s first HAXPES lab system from Scienta Omicron for the Henry Royce Institute in the UK, using a Ga 9.25 keV anode with high enough intensity to make measurements quickly. This opens up analysis of buried layers, layered structures, as well as materials systems with rough and contaminated surfaces, such as batteries. We wanted to quantify atomic concentrations and gauge exactly how deep below the surface we can extract information from, which lead to our collaboration with Prof Tougaard at the University of Southern Denmark. We found it remarkable that we can extract information from up to 20 times the inelastic mean free path of the electron, which translates to hundreds of nanometres for these organic LED materials. We have now generated a library of sensitivity factors for this X-ray source which for easy quantification of every element and every core level, and as such the interest in applying HAXPES for non-destructive chemical composition analysis below the surface is greatly accelerating.  

Authors 

B.F. Spencer ^a,b,*, S. Maniyarasu ^c,d, B.P. Reed ^e, D.J.H. Cant ^e, R. Ahumada-Lazo ^c,d, A. G. Thomas ^a,d, C.A. Muryn ^d,f, M. Maschek ^g, S.K. Eriksson ^g, T. Wiell ^g, T.-L. Lee h, S. Tougaard ⁱ, A.G. Shard ^e, W.R. Flavell ^b,c,d 

Institutes 

a Department of Materials, The University of Manchester, Oxford Road, Manchester, United Kingdom  

b Sir Henry Royce Institute for Advanced Materials, The University of Manchester, Oxford Road, Manchester, United Kingdom  

c Department of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester, United Kingdom  

d The Photon Science Institute, The University of Manchester, Oxford Road, Manchester, United Kingdom  

e National Physical Laboratory, Hampton Road, Teddington, United Kingdom  

f Department of Chemistry, The University of Manchester, Oxford Road, Manchester, United Kingdom 

g Scienta Omicron GmbH, Limburger Strasse 75, Taunusstein, Germany  

h Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, United Kingdom  

i Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, DK-5230 Odense M, Denmark 

URL of Institute web-pages 

https://www.royce.ac.uk/ 

https://www.manchester.ac.uk/ 

Publication(s) 

Applied Surface Science 541 (2021) 148635 

https://doi.org/10.1016/j.apsusc.2020.148635

Instrument 

HAXPES Lab with Ga source and EW4000 at Diamond Light Source (BL I09)