Photoemission
Angle resolved photoemission spectroscopy (ARPES) allows to determine the structure of electronic bands in a crystal. This method consists in sending light on a sample which absorbs it and ejects electrons from its surface, and needs ultra-high vacuum (UHV) condition (10-11 mbar). A photoelectron analyzer collects the ejected electrons and analyzes their kinetic energy and emission angle such that on an ARPES spectrum, the photoelectron intensity is mapped for all emission angles which make the electronic bands of the measured crystal directly visible.
In our lab, ARPES measurements are performed using a Scienta DA30 photoemission analyzer and three different light sources: a He or Xe discharge lamp, an X-ray source and a laser source. The sample is held on a motorized manipulator which profits from six degrees of freedom.
X-ray photoemission spectroscopy (XPS) can also be performed on various materials, allowing a chemical analysis of the measured sample.
Often, the electronic properties of studied materials change with temperature. Thanks to a cryogenic temperature controller, the sample temperature can be easily varied from room temperature to 13 K using liquid helium.
Our experimental setup allows cleaving samples in-situ as well as sputtering and annealing. Two evaporation sources are available to depose elemental metals on sample surface and the sample structure can be analyzed with a low-energy electron diffraction (LEED) device.
A considerable advantage of our experimental setup is that all these different experimental techniques are connected to each other and to the STM via the UHV.