LowDosePES

Low Dose Photoelectron Spectroscopy at PM4

This instrument is dedicated to photoelectron spectroscopy studies at low irradiation doses. Thanks to a fast chopper, the sample is only reached by a single bunch (carrying about two orders of magnitude lower flux than the full multibunch train). Measurements are still efficient thanks to the high transmission of an ArTOF analyser. The wide angle acceptance of the latter also allows angular-resolved photoemission experiments without need for sample rotation. Moreover, a synchronized laser system makes possible excited-state characterization and pump-probe studies with tens of ps resolution.

Methods

NEXAFS, Time-resolved studies, XPS, UPS, ARPES

Remote access

depends on experiment - please discuss with Instrument Scientist

Beamline data
Energy range 20 - 2000 eV
Energy resolution 6,000 at 400 eV
Flux 1e9 - 1e10 phot/s
Polarisation horizontal
Focus size (hor. x vert.) down to 0.1 x 0.1
Phone +49 30 8062 14713
More details PM4
Station data
Temperature range 10-500K. Heating up to 1200 K and flashing up to 1700 K will be possible with the replacement of the current manipulator, planned for 2022.
Pressure range Base pressure within <5x10^-10 and 3x10^-9 mbar. With possibility to dose selected gases.
Detector Scienta ArTOF-10k electron energy analyzer. Under purchase and expected to be available in 2022: an additional hemispherical electron energy analyser as replacement for the Scienta SES-100 currently out-of-order.
Manipulators x,y,z,θ stage with Janis cryostat. Expected to be replaced in 2022 by a new manipulator, currently under purchase, with 6 axes (X, Y, Z, polar, azimuth and tilt) and an extended temperature range.
Sample holder compatibility
  • flag (a.k.a Omicron)-style
  • maximum sample size 10mm x 10mm
Additional equipment • Top preparation chamber: clean sample preparation - MCP LEED, mass spectrometer, many free ports

• Side preparation chamber for non-organic samples – sputter gun, gas inlet, resistive heating up to 900 K, mass spectrometer, storage space for 5 samples (1 heatable, 4 not-heatable), several free ports. By end of 2021, the manipulator of this chamber with be replaced by a new one also allowing for LN2 cooling, electron bombardment heating and direct heating.

• Side preparation chamber for organic samples - quartz microbalance, storage space for 6 samples, several free ports for replaceable evaporators etc

• Synchronized optical laser: 1030, 515 or 343 nm wavelength, >330 fs pulse duration, tuneable repetition rate up to 1.25 MHz

The LowDosePES end-station is permanently installed at the PM4 dipole beamline. 

It is equipped with an angle-resolved time-of-flight (ArTOF) spectrometer, featuring high transmission and wide angular acceptance

Thanks to the high transmission of the ArTOF, faster acquisition times and equally reduced dose rates can be achieved with respect to a hemispherical analyzer, thus making possible photoelectron spectroscopy investigations of materials that usually suffer from radiation damage. 

When further considering its wide angular acceptance, the ArTOF results particularly suitable to track changes in the sample electronic structure as a function of additional parameters, such as gas exposure, temperature or delay after excitation from an optical pump. 

Since the ArTOF needs a pulsed source with repetition rate not exceeding few MHz, a fast mechanical chopper is installed at the intermediate focus of the beamline enabling permanent access to 1.25 MHz -spaced X-ray bunches, not only during single-bunch operation of the storage ring, but also during the more common hybrid operation mode.

When slowed down, the chopper no longer intercepts the beam, and the full filling pattern is delivered to the end-station. This possibility can be used for x-ray absorption spectroscopy measurements in total electron yield.

The end-station has access to a synchronized, ultrafast (pulse length >330 fs), high repetition rate (up to 1.25 MHz), infrared (1030 nm) laser - and its second to third harmonics - for time-resolved laser-pump / x-ray-probe photoemission measurements.

Remote Access Details

Beamline and end-station controls can be operated remotely to a very large extent. While the physical presence of a part of the experimental team is required for sample handling, additional members of the team can be enabled for remote access to the experimental controls.