A compact ultrahigh vacuum x-ray diffractometer for surface glancing scattering using a rotating-anode source

Abstract

A compact ultrahigh vacuum (UHV) x-ray diffractometer was designed and constructed using a small rotating-anode x-ray source of 18 kW. Its UHV specimen chamber is 200 mm high and 140 mm in diameter and can be evacuated up to 3×10−8 Pa. The x ray is incident into the chamber through a thin Be window, 0.2 mm thick and 30 mm in diameter. Diffracted and scattered x rays are taken out through another Be window, 0.4 mm thick and 60 mm in diameter. All the equipment, a rotating-anode x-ray source, an incident monochromator, and a two-circle diffractometer onto which an UHV specimen chamber and a conventional scintillation counter are mounted, are arranged on only one optical table, 70 cm wide and 90 cm in length. Configuration of the specimen holder in the chamber, which is designed for the surface glancing angle scatterings at present, can be controlled from outside of the vacuum. The apparatus is the best suited to in situ observations of growing crystal surfaces during the deposition. A preliminary experiment of the glancing angle scattering of mechanically polished silver polycrystal surfaces gave an order of 103 count s−1 of scattered x-ray intensity at its specular reflection angle, which is enough to derive a significant interpretation of the surface structure.