The SGM4 beamline on ASTRID2
End-station for angle-resolved photoemission (nanoARPES).
The UV focussing optic used in the SGM4 end station is a hollow glass capillary lined with platinum, manufactured by Sigray. This elliptical optic demagnifies the intermediate focus by a factor of 40 onto the sample, for a measured focal spot size of around 4 x 4 µm2. Piezoelectric stick-slip positioners of the capillary and sample holder allows for precise positioning of the beam on the sample with better than 100 nm repeatability.
Schematic of the optical layout of the post focussing optics and nanoARPES endstation.
Photoemission spectra are acquired using a SPECS Phoibos 150 SAL analyser. This analyser is equipped with electron deflector lenses which allow for scanning +/- 15 degrees perpendicular to the entrance slit without moving the sample. This is invaluable as the small spot size precludes rotation of the sample to collect this angular component, as is typically done in ARPES measurement. Such deflector scanning modes are highly versatile and available in all of the analyser lens modes.
The SGM4 end station incorporates turbomolecular and ion pumps to achieve base pressures of 2x10-10 mbar. A micro channel plate (MCP) 150 mm behind the chamber focus allows for characterisation of the capillary beam spot. Samples are held at room temperature for ARPES acquisition. A fast entry load lock with two garage slots allows for annealing of samples using a heating filament, and cleaving of top-posted or taped samples at pressures of 1x10-8 mbar. Samples may also be loaded into the end station via a vacuum suitcase.
Internally, the 6-axis sample holder and 5-axis capillary optic stages are mounted on a pedestal which is mechanically decoupled from the outer chamber, directly mounted onto a zanite block for vibration isolation. This allows for the analyser to be rotated around the sample up to 45 degrees on a rotatable vacuum feedthrough without disturbing the alignment of the beam on the sample. Rotation of the analyser about its axis up to 90 degrees is also available to change the orientation of the analyser entrance slit relative to the sample from horizontal to vertical.
3D model drawing of the 11-axis sample and optics stage.
Both Aarhus style slotted sample plates and a custom designed chip-holding sample plate are compatible with the system. The latter can make up to 4 separate connections for the application of voltages using two Keithley 2450 sourcemeters.
Photo showing the inside of the SGM4 nanoARPES end station.
For further information please contact:
Søren Ulstrup
Jill Miwa
Last Modified 23 October 2023