Photelectron Energy Loss Spectroscopy (XPS-PEELS)

Photoelectron Energy Loss Spectroscopy (XPS-PEELS) has a double interest, since it gives access to both chemical composition and electronic properties of a solid. The dielectric function of the solid surface (depth ~ 5 nm) over a large energy range (0-50 eV) can be retrieved from the energy distribution of inelastically scattered photoelectrons that excite volume and surface plasmons, as observed in XPS experiments.
 

Energy loss spectrum of C1s photoelectrons  - for a PLD amorphous carbon film terminated by a grafted alkyl monolayer with ester end-groups (3.7×1014 cm-2). Volume and surface losses were measured as a function of the off-normal emission angle: α = 0, 45, 55, 65, 75 degrees.

A first version of the PEELS algorithm has been tested using model materials (amorphous silicon, polycrystalline diamond), along with amorphous carbon films, before and after covalent immobilization of molecular monolayers. Recently, a Fourier transform method has been developed to extend this method to metal surfaces.

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