The Bloch beamline is dedicated to high resolution angle-resolved photoelectron spectroscopy (ARPES) for studying the electronic structure of surfaces and 2D materials. Bloch is optimized for a photon energy range of 10-200eV, and features a spot size down to 10μm x  10μm. Both linear and circular polarized light can be provided, and with substantially reduced flux the beamline can source photon energies up to 1000eV, enabling core level spectroscopy of most elements.

Branchline 1 has an endstation comprehensively configured for ‘standard’ ARPES experiments. Six ultra-high vacuum coupled chambers provide ample opportunities for sample preparation and offline characterization with LEED and STM. The analysis chamber is equipped with a fully motorized six-axis manipulator, with a closed-cycle cryostat capable of arbitrary sample temperatures down to 20K. The electron analyzer is a high performance DA30 hemispherical analyzer from ScientaOmicron. Here the electronic deflection mode enables Fermi surface mapping without needing to rotate the sample, which combined with the small spot size is highly advantageous for studying small or inhomogeneous samples.

The branchline 2 endstation is currently in the installation and commissioning stage, and is expected to be available to general users by early 2022. This branchline will be dedicated to spin-resolved ARPES measurements, using a high efficiency VLEED detector and spin rotator from SPECS capable of resolving all three spin components.

Techniques

Available forTechnique description
General UsersHigh-resolution angle resolved photoelectron spectroscopy (ARPES), using deflection based analyzer or 6-axis manipulator.
General UsersLinear vertical or horizontal polarised light from EPU, with energy range 10-1000eV (peak flux and resolution 15-200eV).
General UsersOnline Scanning tunneling microscopy (STM), 50K - 300K.
Commissioning expertsSpin-resolved ARPES with a 3D-VLEED detector

2021-10-25

Zigzag graphene nanoribbons’ surface state hints at spin-polarized channels’ potential practical applications

An international team of researchers confirmed that epitaxial zigzag graphene nanoribbons grown on mesa-structured silicon carbide form protected spin-polarized transport channels at room temperature with very weak spin–orbit interaction. They discovered that while the zigzag graphene nanoribbon monolayer sank almost completely into a silicon carbide facet, its lower edge dissolved and mixed with the silicon

Image: Empa