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Inelastic background modelling applied to Hard X-ray Photoelectron Spectroscopy of deeply buried layers: a comparison of synchrotron and lab-based (9.25 keV) measurements

DOI: 10.1016/j.apsusc.2020.148635 DOI Help

Authors: B. F. Spencer (he University of Manchester,) , S. Maniyarasu (The University of Manchester) , B. Reed (National Physical Laboratory) , D. J. H. Cant (National Physical Laboratory) , R. Ahumada-lazo (The University of Manchester) , A. G. Thomas (The University of Manchester) , C. A. Muryn (The University of Manchester) , M. Maschek (Scienta Omicron GmbH) , S. K. Eriksson (Scienta Omicron GmbH) , T. Wiell (Scienta Omicron GmbH) , T.-l. Lee (Diamond Light Source) , S. Tougaard (University of Southern Denmark) , A. G. Shard (National Physical Laborator) , W. R. Flavell (The University of Manchester)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Applied Surface Science

State: Published (Approved)
Published: December 2020
Diamond Proposal Number(s): 20059

Abstract: Hard X-ray Photoelectron Spectroscopy (HAXPES) provides minimally destructive depth profiling into the bulk, extending the photoelectron sampling depth. Detection of deeply buried layers beyond the elastic limit is enabled through inelastic background analysis. To test the robustness of this technique, we present results on a thin (18 nm) layer of buried metal-organic complex buried below up to 200 nm of organic material. Overlayers with thicknesses 25-140 nm were measured using photon energies ranging 6-10 keV at the I09 end station at Diamond Light Source, and a new fixed energy Ga Kα (9.25 keV) laboratory-based HAXPES spectrometer was also used to measure samples with overlayers up to 200 nm thick. The sampling depth was varied: at Diamond Light Source by changing the photon energy, and in the lab system by performing angle-resolved measurements. For all the different overlayers and sampling depths, inelastic background modelling consistently provided thicknesses which agreed, within reasonable error, with the ellipsometric thickness. Relative sensitivity factors were calculated, and these factors consistently provided reasonable agreement with the expected nominal stoichiometry, suggesting the calculation method can be extended to any element. These results demonstrate the potential for the characterisation of deeply buried layers using synchrotron and laboratory-based HAXPES.

Journal Keywords: Hard X-ray photoelectron spectroscopy; Depth profiling; Inelastic background analysis; Buried interface; Angle-resolved photoelectron spectroscopy; Metal-organic complex

Subject Areas: Technique Development, Physics, Materials

Instruments: I09-Surface and Interface Structural Analysis