HE-SGM

NEXAFS/XPS spectroscopy /HE-SGM

The instrument HE-SGM at the HE-SGM beamline is optimized for NEXAFS and XPS spectroscopy in the VUV range. It is designed to cover the light elements (C, N, O and F) K-edges which contain important spectroscopic information in soft matter samples, carbon (nano) materials and molecules adsorbed on catalytically relevant surfaces. Oxygen plasma cleaning has removed carbon contamination from the beamline’s optical elements resulting in a crucial decrease of parasitic contributions to the experimental data and hence allowing proper measurements of organic molecular thin films with a thickness down to 0.1 monolayer.

The beamline monochromator allows for fast scanning over the energy range (155 - 750 eV).

• Metal-organic frameworks and their loading with gases and metal nanoparticles
• Novel carbon-based materials (including their functionalization)
• Dipole control at surfaces and interfaces using monomolecular films
• Development of NEXAFS and XPS methods for the characterization of bio-sensing platforms
• Ultra-thin molecular and polymeric membranes

Fig.1 HE-SGM experimental station

Methods

XPS, NEXAFS

Remote access

not possible

The NEXAFS/XPS experimental station is a multi-chamber UHV system produced by PREVAC (Poland) and consists of the following chambers:

1. Two load-locks: the first one is used for fast sample exchange with a storage facility of up to six samples; the second one is used for sample exchange with a storage facility for two sample holders and with an opportunity to install a special vacuum transfer box allowing to transport samples under UHV conditions. Moreover, the park station connected to the distribution chamber allows the storage of six additional sample holders under UHV conditions.

2. The unique sample transfer system including the distribution chamber of the carrousel-type (a base pressure better than 10^-10 mbar) and manipulators allow fast (less than 1 minute) transfer of samples from one chamber to another. It was established that during the sample transfer in the cold state (~100 K) the temperature doesn't increase by more than 20 K.

3. A versatile preparation chamber operated at a base pressure of better tha 5x10^-10 mbar accepting up to 3 evaporators for metals or organics and/or other sources (for example, atomic H source, etc.), two sputter guns, gas dosing systems, as well as an LEED system for control of sample quality. One of the evaporators is permanently installed and available to all HE-SGM users. A special receiving station of the manipulator allows for cooling with liquid nitrogen to 100 K and for heating up to 2000 K.

4. A main chamber with base pressure of better than 10^-10 mbar is equipped with a hemispheric electron energy analyser (Scienta SES 3000), a sputter gun, and a home-built double channel plane detector enabling NEXAFS spectroscopy in partial electron yield (PEY) or total electron yield (TEY) mode. The energy analyser and the MCP-NEXAFS detector can be read out at the same time thus allowing simultaneous recording of integrated secondary electrons (PEY or TEY) and energy-resolved Auger electrons. For the measurements the sample is transferred to a 5-axes manipulator with three translational and two rotational (polar and azimuthal) degrees of freedom. A continuous-flow liquid He cryostat installed in the chamer allows sample cooling down to 30 K, while samples can be heated up to 2000 K (depending on the sample holder).

Further instrument applications:

• Adsorption of organic molecules on metal oxides
• SR-XPS and NEXAFS investigation of ionic liquids
• Charge transfer dynamics in molecular films
• Optically controlled molecular switches
• Novel molecular functional films
• Lithography with a monomolecular resist
• Metallo-organic oligomeric films: design and applications