Angular and Momentum Resolution of the ASTRAIOS 190 2D-CMOS
During the acceptance tests at customer's site, our ASTRAIOS 190 2D CMOS analyser has proven its superior electron imaging quality. The ARPES data show perfect parallel lines of 0.18° width. The angular resolution is better than 0.07°.
In todays blog post we are proud to share some recent experimental results demonstrating the superior electron imaging quality of the ASTRAIOS 190 2D-CMOS analyzer. The ASTRAIOS combines a wide acceptance angle lens with a single shifting electrode, that accepts electrons within an emissions cone of up to ± 30°, in an angular resolved mode, with an excellent angular and momentum resolution. This unique combination makes it the perfect tool for the most demanding angular-resolved photoemission spectroscopy (ARPES) experiments.
The first figure contains data taken from a test aperture generating a distinct emission pattern of electrons emitted by a Mo wire once illuminated by an electron gun. The test aperature is shown at the bottom of the figure. Considering the small but finite size of the emission spot and the size of the test slits, a pattern of 15 parallel stripes with an angular width of 0.17° each and a maximum emission angle of ±16° is generated. The corresponding ARPES data (left panel of the figure) show perfectly parallel lines with a width of 0.18°, leading to an angular resolution of the ASTRAIOS being better than 0.07°.
Such experiments are essential to specify the analyzer performance. But finally experiments resulting in band structure measurements like those performed in laboratories and synchrotrons all over the world are of real scientific interest to customers and users of such analyzers.
Thus here, we demonstrate the excellent imaging properties of the ASTRAIOS demonstrated using ARPES data taken on Graphene/SiC at room temperature with a small spot lab-based UV source operated at He II excitation energy (40.81eV). Different cuts through a 4-dimensional data set are shown. In the left panel we see a constant energy cut slightly below the Fermi level of the sample and above its Dirac energy. We measure a FWHM of the Graphene bands of 0.005 Å-1. Assuming that the momentum width of this band is on the order of the analyzer k-resolution, we get a real-life k-space resolution of <0.003 Å-1. This data has been taken at a customer site during the site acceptance test experiments.
More exciting data have been taken and will be posted as news during the following weeks. Stay tuned.