A COMPACT UHV X-RAY DIFFRACTOMETER FOR STUDYING SURFACES AND INTERFACES

A compact ultra-high-vacuum (UHV) X-ray diffractometer for surface gla ncing X-ray scattering has been constructed. All the equipment, includ ing a rotating-anode source of 18 kW and a UHV specimen chamber, is ar ranged on one optical table of dimensions 70 x 90cm. The specimen cham ber is 14cm in diameter and 20 cm high and can be evacuated up to 3 x 10(-8) Pa. It is equipped with two Be windows of thicknesses 0.2 and 0 .4 mm. Specimen orientation in the vacuum is controlled from the outsi de. The specimen can be heated up to 773 K. The chamber has two evapor ation cells and can be used for in situ observations of growing crysta l surfaces. Using this instrument, we observed a mechanically polished Ag surface and successfully made an in situ observation of the layer- by-layer growth of a PbSe(111) surface. The instrument will be useful for preliminary experiments using laboratory sources, prior to final m easurements at synchrotron radiation facilities.