Electron spectrometers with are available now which have a resolution of not more than 50
meV at kinetic energies up to 15 keV. This high kinetic energy photoemission at hard x-rays
(HIKE or HAX-PES) is an ideal – non-destructive - tool to look deeply into bulk material (>5
nm) and to study (buried) interface layers. For this technique hard x-rays with similar ultra-
high energy resolution at high flux are required.
The BESSY bending magnet beamline KMC-1 /1/ is used successfully for this HIKE
technique employing an R-4000 analyzer /2/. Despite of the low photoelectron cross sections
at high excitation energies, e.g. core levels of multilayer interfaces and “real” solar cell
samples at probing depths of more than 10 nm can be investigated /3/.
The reason for the good matching of this beamline to the experimental requirements is due to
the facts that this beamline not only has a high flux (1011-1012 photons/sec) in a focus size,
which is well matched to the spectrometer acceptance, and a continuously tuneable working
range between 1.7 and 12 keV, which fits ideally to the HIKE requirements, but also a very
good energy resolution.
The crystal optics is optimised to the soft x-ray range which requires Bragg angles of up to
82o. This “built-in” normal incidence crystal optics is intrinsically connected with a high
energy resolution according to !
E $of up to 120.000 at selected energies. Thus
any flux-consuming post-monochromatization employing Si (nnn) channelcut crystals is
It will be shown, that soft x-ray bending magnet beamlines at medium energy storage rings
provide good opportunities for HIKE photoelectron spectroscopy.
/1/ F. Schaefers, M. Mertin, M. Gorgoi, Rev. Sci. Instrum. 78, 123102-1-14 (2007) URL
/2/ M. Gorgoi et al., Nucl. Instrum. Meth., A601, 48–53 (2009), URL:
/3/ E. Holmstroem et al., Phys. Rev. Lett. 97, 266106-1-4 (2006)