ISISS

Innovative Station for In Situ Spectroscopy

ISISS (Innovative Station for In Situ Spectroscopy) is a project of the Inorganic Chemistry department of the Fritz-Haber-Institut der Max-Planck-Gesellschaft (FHI), Max Planck Institute for Chemical Energy Conversion (MPI-CEC), and HZB/BESSY II in Berlin. The scientific aim at ISISS – an instrument dedicated to near ambient pressure XPS (NAP-XPS) experiments - is to study the electronic surface/near surface structure of functional materials in the presence of a reactive environment. This includes both gas/solid interfaces (e.g. heterogeneous catalysis) and liquid/solid interfaces (e.g. catalytic water splitting).

The working area of the facility is material science in general and catalysis in particular. Our approach includes 3 units that have to complement on another: a state of the art soft X-ray beamline, an endstation for ambient pressure X-ray photoelectron (NAP-XPS) and X-ray absorption spectroscopy (XAS), and an infrastructure on site to perform experiments with a chemical background. In contrast to standard vacuum surface science experiments, in situ experiments require the installation of a complex gas feed and an elaborated gas analytic to follow the conversion of the gas phase during the reaction.

Selected Applications:
  • X-ray photoelectron spectroscopy (XPS) under high vacuum (p=10^(-8) mbar) and near ambient pressure conditions (typically 1 mbar)
  • X-ray aborption spectroscopy (XAS) at pressure up to 10 mbar with NAP-HE-XPS endstation
Fig. 1: picture of NAP-HE-XPS (courtesy of SPECS GmbH, Berlin) <br><br><br>

Fig. 1: picture of NAP-HE-XPS (courtesy of SPECS GmbH, Berlin)



Methods

NAP-XPS, XPS, NEXAFS, Time-resolved absorption, Mass Spectrometry

Remote access

not possible

Instrument data
Phone (~49 30 8062-) 14905, 14906
Beam availability 24h/d
Source D41 (Dipole)
Monochromator PGM
Energy range (at experiment) tbd
Energy resolution >15,000 at 400eV
Flux 6x1e10 photons/s/0.1A with 111µm exit slit
Polarisation linear horizontal
Focus size (hor. x vert.) 100x80 µm2
Temperature range room temperature up to 1000 K
Pressure range Maximum pressure: 20 mbar
Minimum pressure: 10-8 mbar
Typical pressure: 1 mbar

For more details contact the instrument scientist.
Detector 2D delay line detector (2D DLD) (SURFACE CONCEPT, Mainz)
Manipulators various, exchangeable with optimised for sample environments
Sample holder compatibility Homemade concept. Check text below. For more details contact the station manager.
Additional equipment
Additional information Further details: beamline ISISS
Fig. 2: Scheme of the NAP-HE-XPS endstation installed at the ISISS beamline. <br>The spectrometer (right site) is displayed retracted from the XPS cell module (left side). <br><br><br>

Fig. 2: Scheme of the NAP-HE-XPS endstation installed at the ISISS beamline.
The spectrometer (right site) is displayed retracted from the XPS cell module (left side).


Table 1: Gas analytics<br><br><br>

Table 1: Gas analytics


Table 2: Laboratory facilities at ISISS<br><br><br>

Table 2: Laboratory facilities at ISISS



The beamline has to accommodate for a variety of user requirements resulting from the scientific approach as outlined above. The basic design considerations are as follows: 

  • A variety of materials with a large diversity in composition should be characterised and diverse scientific problems should be tackled. This requires a beamline that is adaptable to the needs of the users. This comprises a high flexibility concerning the provided photon energy range and spectral resolution.
  • Due to the compounds usually studied in catalyst research, the available photon flux at energies between 400 eV and 1200 eV is the main concern covering e.g. the C1s, N1s, O1s and transition metal 2p core levels.
  • The X-ray spot size at the sample position is optimised for a best fit to the electrostatic lens system of the in situ apparatus and the electron analyser.
  • The beamline should be easy to handle to allow for multi-user operation without elaborated knowledge of technical details.
  • An accurate and reliable energy calibration should be feasible as an essential part of high quality XPS studies.

The design considerations resulted in the selection of a plane grating monochromator (PGM). This PGM design is a development based on the Petersen type monochromator at BESSY at which the light is colliminated in the dispersive plane in front of the grating by the mirror M1. In this design, the fix focus constant c = (cos β / cos α) (α: angle of incidence, β: angle of diffraction relative to the grating normal, respectively) is kept constant during the scanning of the photon energy. This allows the free adjustment of the fix-focus constant without movement of the exit slit which can be used to easily optimise the monochromator to the requirements of the users.