Soft X-ray ARPES for three-dimensional crystals in the micrometre region.

An endstation dedicated to angle-resolved photoemission spectroscopy (ARPES) using a soft X-ray microbeam has been developed at the beamline BL25SU of SPring-8. To obtain a high photoemission intensity, this endstation is optimized for measurements under the condition of grazing beam incidence to a sample surface, where the glancing angle is 5° or smaller. A Wolter mirror is used for focusing the soft X-rays. Even at the glancing angle of 5°, the smallest beam spot still having a sufficient photon flux for ARPES is almost round on the sample surface and the FWHM diameter is ∼5 µm. There is no need to change the sample orientation for performing kx - ky mapping by virtue of the electron lens with a deflector of the photoelectron analyzer, which makes it possible to keep the irradiation area unchanged. A partially cleaved surface area as small as ∼20 µm was made on an Si(111) wafer and ARPES measurements were performed. The results are presented.