Ultrahigh-spatial-resolution chemical and magnetic imaging by laser-based photoemission electron microscopy

Abstract

We report the first experiments carried out on a new chemical and magnetic imaging system, which combines the high spatial resolution of a photoemission electron microscope (PEEM) with a continuous-wave deep-ultraviolet laser. Threshold photoemission is sensitive to the chemical and magnetic structures of the surface of materials. The spatial resolution of PEEM is limited by space charging when using pulsed photon sources as well as aberrations in the electron optics. We show that the use of a continuous-wave laser enabled us to overcome such a limit by suppressing the space-charge effect, allowing us to obtain a resolution of approximately 2.6 nm. With this system, we demonstrated the imaging of surface reconstruction domains on Si(001) by linear dichroism with normal incidence of the laser beam. We also succeeded in magnetic imaging of thin films with the use of magnetic circular dichroism near the Fermi level. The unique features of the ultraviolet laser will give us fast switching of the incident angles and polarizations of the photon source, which will be useful for the characterization of antiferromagnetic materials as well as ferromagnetic materials.

Selective Formation of Zigzag Edges in Graphene Cracks

“…40 Raman spectra were acquired using a micro-Raman spectroscope (Renishaw, inVia) with an excitation laser operating at 532 nm. Prior to observations, the graphene was transferred to In the numerical simulations, the model consisted of linearly-distributed particles connected with springs and having free ends.…”

HERMES: a soft X-ray beamline dedicated to X-ray microscopy

“…This is almost true in all fields of science such as material and nanoscience, biology and medicine, chemistry, earth and environmental science etc. In turn, the advent of ultra-bright third-generation synchrotron radiation sources has opened the route to X-ray microscopy and imaging with resolution in the 10 nm ranges (Chao et al, 2005;Tromp et al, 2013;Schmidt et al, 2005Schmidt et al, , 2013Taniuchi et al, 2015). In particular, soft X-ray microscopy is probably among the most suitable methods to respond to that demand.…”

New developments in laser-based photoemission spectroscopy and its scientific applications: a key issues review

“…To overcome the space charge effect, it is desirable to increase the repetition rate of the laser light sources in order to reduce the number of photons in one pulse. Development of continuous-wave laser light will be most ideal because in principle it does not produce space charge effect[37,55,183]. The continuous-wave laser light may become particularly useful for spin-resolved ARPES where high photon flux is necessary in order to compensate the low efficiency of spin detectors which will inevitably causes strong space charge effect if it is a pulsed laser light source.Spatially-resolved ARPES will play an important role in studying inhomogeneous systems.…”