Surface characterization of silicon spheres by combined XRF and XPS analysis for determination of the avogadro constant

For the quantitative surface characterization of a monocrystalline silicon sphere PTB has constructed and taken into operation an analytical instrumentation, which combines X-ray fluorescence and X-ray photoelectron spectroscopy techniques. The main objective of this novel instrumentation is the characterization of the oxide layer and unintentional contaminations, e.g. from hydrocarbons. It is equipped with a ball manipulator allowing to measure at each point on the surface of ball-shaped sample with a diameter of about 93.6 mm. Monocrystalline silicon spheres with this diameter allow a realization of the SI-base unit of the mass.