A NEW APPARATUS FOR SURFACE X-RAY-ABSORPTION AND DIFFRACTION STUDIES USING SYNCHROTRON-RADIATION

A new apparatus for structural studies of surfaces and buried interfac es using synchrotron radiation was built and tested at the 27-pole wig gler station BL13B of the Photon Factory. The apparatus was designed t o 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) so lid-state detector array for a fluorescence yield measurement and a hi gh precision eight-axis goniometer in the UHV chamber with a base pres sure of 1X10(-10) Torr. For the same sample mounted on the in-vacuum g oniometer, 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 polari zed surface-sensitive XAFS. The results show that the apparatus can pr obe the local structure of adatoms with similar to 0.1 monolayer sensi tivity. (C) 1995 American Institute of Physics.