X-ray Photoelectron and Absorption Spectroscopy with variably polarized light

At a 150-1600 eV photon energy range synchrotron radiation



The APE-HE (High Energy) endstation in ultra high vacuum condition is devoted to the investigation of the magnetic and electronic properties of surfaces, interfaces and nanostructures via X-ray Photoelectron Spectroscopy (XPS), X-ray Absorption Spectroscopy (XAS) and X-ray Magnetic Circular Dichroism (XMCD) analysis.

X-ray Photoelectron Spectroscopy (XPS) at APE-HE can be exploited as a surface chemical analysis technique: the valence band DOS reveals the orbital contributions through cross-section analysis (photon energy dependence) and core level photoemission is sensitive to the local environment of a given atomic specie in the sample or at the surface. The photon energy range available allows to excite relatively deep core levels (up to 1600 eV) or to have relatively high kinetic energies for shallow core levels, probing variable depths of the material.


APE-HE end station for XAS/XMCD/XPS measurements is a UHV chamber equipped with a 4 axis manipulator and an hemispherical electron energy analyzer. It is built as a vibration-free sample chamber with mu-metal shielding for reducing the background H-field. The sample manipulator allows X-Y scanning on the surface with 1 micrometer precision and is therefore suitable to perform experiments on microstructures. The sample environment allows for temperature control (He-flow cryostat and heating stages) with feedback, for H-field application in the surface plan up to 0.1 T and for E-field application up to 500 V between contacted surfaces and substrate. The total electron yield (TEY) detection is achieved by measuring the drain current with a high sensitivity electrometer through highly shielded connections, or with an in vacuum electron multiplier. The total fluorescent yield (TFY) detection is achieved by an in-vacuum photodiode. Continuous scanning of the monochromator for XAS spectra is available for superior speed. Step-by-step scanning is also available and used to perform highly sensitive XMCD while switching the in-plane magnetization of the sample at each point.

Two independent electrical connections on the measuring position of the sample allow applying electric bias during or in-between the measurement. The possibility of combining electric and magnetic fields allows studying the chemical and magnetic behaviour of multiferroic materials and heterostructures.

XY manipulator scan of a pattern of oxide rectangles (300 x 100 mm2) in metallic frame. The image has been obtained by measuring the drain current of the sample.
XAS and XMCD spectra of a 0.5 nm Co film deposited on iron substrate recorded by reversing the in-plane magnetization at each point.