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Technical Information - Soft X-ray
Soft x-ray spectroscopy

Technical Information - Soft X-ray

Main Experimental Techniques

Angle Resolved Photoelectron Spectroscopy (ARPES)

X-ray Photoelectron Spectroscopy (XPS)
Near Edge X-ray Absorption Spectroscopy (NEXAFS) in the following modes:

  • Total Electron Yield (TEY)
  • Partial Electron Yield (PEY)
  • Total Fluoresence Yield (TFY)

Instrument control

  • FMB Beamline Software and EPICS Qt framework (beamline control and NEXAFS measurement)
  • SPECSlab Prodigy (X-ray Photoelectron Spectroscopy measurement)
  • LabVIEW (ARPES measurements)

Energy range

In order to achieve an x-ray beam of adequate stability and energy resolution, the energy range of the SXR beamline is restricted to 90-2500 eV.

The insertion device is a variable polarisation undulator, called an AppleII undulator, capable of supplying linear vertical, linear horizontal, left and right circularly polarised light. The device works in the 1st, 3rd and 5th harmonics. Elliptically polarising undulators are currently the most advanced general-purpose insertion devices. The provision of circularly polarised light ensures that the beamline is sufficiently flexible to cater for future developments in the scientific areas of interest to the Australian user community.

The resolving power of the SXR monochromator is 10,000, which is relatively easy to achieve with modern monochromators.

Beamline specifications

Source

Elliptically polarised undulator

Energy range

 81 -2500 eV

Optimal Energy range

85 – 2000 eV

Resolution deltaE/E

Between 5000 and 10,000

Nominal beam size at sample (horizontal x vertical)

Spectroscopy

High throughput NEXAFS

 

 

0.15 mm by 0.05 mm

1 mm by 1 mm

Flux at 400 keV 

Between 3x1012 and 5 x1011 Photons/s/200mA at the sample

 

Photon Source Specifications 

 

 SourceElliptically Polarised Undulator
Full polarisation of the source
 
 Period  75mm
 Length 2.012 m
 K 4.8

The soft x-ray spectroscopy end stations

A soft x-ray beamline and end-station must be maintained under a clean, ultra high vacuum (UHV).

There must be vacuum continuity between the analysis chamber and the synchrotron ring. Therefore, the vacuum in the beamline and end-station must be comparable with that in the ring, in terms of both pressure and quality. It is important that the UHV in both the beamline and end-station be as carbon-free as possible, not only to maintain the reflectivity of the optical components at higher photon energies, but also to facilitate XAS at the carbon K-edge.

The necessity to work under clean UHV conditions means that synchrotron soft x-ray spectroscopy is more demanding and time-consuming than hard x-ray spectroscopy. As a consequence, typical beam access periods are longer, and fewer users can be accommodated.

 

Prevac Endstation

The Prevac soft x-ray spectroscopy end-station was built in Germany at a cost of ~$A1m and completed in 2004. It was used at the NSRRC in Taiwan until the Australian Synchrotron became operational. This end-station has been designed and constructed to meet the stringent vacuum requirements noted above. In particular, the vacuum system is as carbon-free as possible. The end-station is comprised of multiple connected UHV chambers allowing for the preparation and subsequent analysis of samples without exposure to air. In addition the end-station allows for investigation of specimens that must be maintained at a low temperature while they are under vacuum, in order to retain moderately volatile material that might otherwise sublime or desorb.

Detectors
  • SPECS Phoibos 150 Hemispherical Analyser
  • Retarding Grid Analysers (Partial Electron Yield and Fluoresence Yield modes)
  • Drain Current
  • Photodiode
Samples
Environment

Ultra High Vacuum (UHV) environment, base pressure 1 × 10-10 mbar

Preparation facilities
  • Sample cooling to approximately 130K (using LN2)
  • Flood gun
  • Ability to transfer samples hot and cold
  • Rotary distribution chamber
  • Fast sample entry load-lock
  • Sample fracture chamber and sample parking chamber
  • Preparation chamber featuring: electron beam evaporator source, Argon ion sputtering, Quartz crystal monitor, Low Energy Electron Diffraction (LEED), gas handling and introduction system, 4 point probe, Kelvin probe

Click here for information on safe transport and handling of samples.

Data analysis
Data formats
  • NEXAFS data from beamline software: *.mda, ASCII
  • XPS data from SPECSlab Prodigy: Delimited text, VAMAS
Analysis software
  • CasaXPS
  • Qant

 

Toroidal Analyser

The toroidal analyser endstation is a custom spectrometer built by La Trobe University, for performing ARPES measurements. The unique toroidal electrode geometry allows for rapid and wide momentum space mapping. The system is moved onto the Spectroscopy Branchline during beamtimes, and in between beamtimes is able to perform offline ARPES measurements using a high intensity vacuum ultraviolet lamp. Recent addition to the system include a scanning tunnelling microscope (STM) and 2D delayline detector. The system features a dedicated chamber for sample growth, preparation cleaning, cleaving. Sample can be cooled to cryogenic temperature for measurement. The toroidal analyser is an advanced instrument, and requires users with UHV experience to be able to run properly.

Detectors
  • Angel resolving electron energy analyser
Samples
Environment

Ultra High Vacuum (UHV) environment, base pressure 1 × 10-10 mbar

Preparation facilities
  • STM
  • LN and LHe cooling capabilities
  • LEED
  • Ar sputter gun

Click here for information on safe transport and handling of samples.

Data analysis
Data formats
  • Custom format
Analysis software
  • Igor Pro

 

High throughput NEXAFS chamber

A high throughput NEXAFS chamber has recently been constructed inline upstream on the Imaging branchline. This chamber allows for batching of multiple samples for automatic scanning. The system is built for samples that are not compatible with ultra-high vacuum (samples can be scanned at a pressure of 10-6 mbar) and is ideal for beam sensitive samples.

Detectors
  • Hemispherical Analyser (Auger Electron Yield mode)
  • Retarding Grid Analysers (Partial Electron Yield and Fluoresence Yield modes)
  • Drain Current
  • Photodiode
Samples
Environment

High Vacuum (HV) environment, base pressure 1 × 10-7 mbar. Room temperature samples only

Preparation facilities
  • Flood gun
  • Sample transfer carousel
  • Easy sample loading
  • Batch scanning

Click here for information on safe transport and handling of samples.

Data analysis
Data formats
  • NEXAFS data from beamline software: *.mda, ASCII
Analysis software
  • Qant