Time-of-Flight Momentum Microscope With Spin Imaging Option

Momentum microscopy and spectroscopy system: Time-of-Flight and parallel imaging spin analyzers based on the parallel working, patented, Ir or Ir/Au spin filter principle.

Time-of-Flight Momentum Microscope

The patented [patents DE102013005173C5 and DE102014018555B3] Time-Of-Flight Momentum Microscope images the full emission hemisphere (2πk²) k-space out of a selectable real space sample area down to a diameter of <1µm, a novel type of ARPES.

  • Momentum resolution <0,01Å-1
  • Spatial resolution <50nm
  • Energy resolution <20meV
  • L-He cooled sample stage available
  • Parallel spin imaging option available

The ToF Momentum Microscope works this way: The zoom optics 1 select a real-space sample area, the switching between real-space and k-space-image is done by the zoom optics 2.

[Medjanik et al., Nature Materials, 16(6):615-621(2017)]

The user can access the full space of the photoemission paraboloid from work function cut-off to Fermi edge during one measurement (approved for excitation energies up to 21.7eV). The optics is isogenic in k for a wide range of energies.

Technical specifications for a complete Momentum Microscope system including the hexapod sample stage.

ToF Momentum Microscope
Energy resolution < 20 meV (17 meV shown with Drift Voltage 10 V)
Simultaneously focused energy rangeUp to 10 eV
Momentum resolution< 0.01 Å-1
Momentum resolved range+- 3 Å-1
Lateral resolution< 50 nm
Real space field of view11....1000 μm
Piezo driven contrast aperture3 aperture sizes and a 200 mesh, x/y adjustable
Piezo driven field aperture9 aperture sizes (down to 10 μm possible and a 200 mesh, x/y adjustable
Motorized manipulator6 axis (Hexapod) which makes in situ sample tilt adjustment possible (e.g. for cleaved samples)
Temperature range< 15 K....400 K (9 K shown)

Constant-energy maps measured at various photon energies of Re (0001).

[H.J. Elmers et al. PhysRevResearch.2.013296]

Real space image of an Au on Si (Chessy) sample.
FoV 11 µm.

The EPICS (https://epics-controls. org) based software supports fully remote controlled measurements via PC. The server-client architecture enables customized, automatic measurement routines via user scripts.

You can integrate additional customer specific devices by implementing further EPICS modules.

Hexapods for Time-of-Flight Momentum Microscope

The Hexapod is a L-He cooled  6-axis sample stage, reaching temperatures < 15K (lowest value shown < 9K). It enables very precise sample positioning, including rotation and tilt up to ±5°. Each axis is equipped with a position readout. Therefore the user can store sample positions which can be recalled later on.

Imaging Spin Detector for Time-of-Flight Momentum Microscope

The Imaging Spin Filter is an upgrade for an existing ToF Momentum Microscope. The spin imaging is based on a parallel working, patented [patents DE102013005173C5 and DE102005045622B4], Au/Ir spin filter principle.

Working principle of the parallel spin analyzer. The instrument works either as a conventional ToF Momentum Microscope in the straight branch or the spin filter crystal deflects the image for spin analysis in the perpendicular branch (spin-filtered branch).

[H.J. Elmers et al., Phys. Rev. Research 2, 013296 (2020)]

Constant-energy maps of Re (0001) measured with photon energies of 18.5 eV. Left to right binding energies 0mV, 200 meV and 400 meV. The lower row displays the spin filtered measurements.

[H.J. Elmers et al., Phys. Rev. Research 2, 013296 (2020)]

An image with a FoV 450µm of a chessy sample with >9.000 pixels in the complete image. This demonstrates the image quality of the spin-filtered branch.