SPELEEM: INTRODUCTION 

Specifications | Description | Operation modes | XPEEM and LEEM methods

The first branchline of the Nanospectroscopy beamline hosts the spectroscopic photoemission and low energy electron microscope (SPELEEM III, Elmitec GmbH), the commercial version of the spectro- microscope developed in the '90s by Ernst Bauer and his co-workers. The SPELEEM combines into one single instrument a low energy electron microscope (LEEM) and an energy filtered x-ray photoemission electron microscope (XPEEM).

The true strength of SPELEEM is the unique combination of complementary imaging and diffraction methods available. By using photons or electrons as probe, SPELEEM allows a real multi-technique approach to the study of surfaces and thin films. XPEEM exploits the characteristics of synchrotron radiation to implement laterally resolved version of x-ray absorption spectroscopy (XAS) and x-ray photoelectron spectroscopy (XPS).

In combination with magnetic linear and circular dichroism (MLD and MCD respectively), the SPELEEM can image the magnetic state of surfaces, thin films and buried interfaces. Due to the wide energy range provided by the beamline, 50-1000eV, the microscope can access most of the relevant absorption edges of transition metals.

By using the hemispherical electron energy analyser the microscope allows core level and valence band imaging, thus probing the local chemical state and electronic structure respectively. The SPELEEM can perform energy-filtered XPEEM with an energy resolution of ~ 300 meV in imaging mode, achieving routinely a lateral resolution of about 40 nm.

LEEM is often used as a complementary technique, being well suited to tackle dynamical processes in force of the high temporal and structural sensitivity. Along with LEEM and XPEEM imaging, related diffraction methods are available. Microprobe low-energy electron diffraction (µ−LEED) and microprobe angle-resolved photoemission spectroscopy (µ−ARPES) allow a characterisation of the crystal and electronic structure in the momentum space. These measurements are restricted to an area of about 2µm in diameter.