A new apparatus for surface x-ray absorption and diffraction studies using synchrotron radiation

Abstract

A new apparatus for structural studies of surfaces and buried interfaces using synchrotron radiation was built and tested at the 27-pole wiggler station BL13B of the Photon Factory. The apparatus was designed to combine x-ray absorption fine structure (XAFS), x-ray standing wave (XSW), and surface x-ray diffraction techniques in the same ultrahigh vacuum (UHV) chamber. The apparatus features a seven-element Si(Li) solid-state detector array for a fluorescence yield measurement and a high precision eight-axis goniometer in the UHV chamber with a base pressure of 1×10−10 Torr. For the same sample mounted on the in-vacuum goniometer, vertically or horizontally polarized surface-sensitive XAFS, surface x-ray diffraction, and XSW can be measured. As a performance test, the structure of Ge overlayers on Si(001) was studied by polarized surface-sensitive XAFS. The results show that the apparatus can probe the local structure of adatoms with ∼0.1 monolayer sensitivity.