Surface layer analysis of Si spheres both in vacuum and in air by an improved ellipsometer

For the new definition of the kilogram, surface analysis of Si spheres is essential to determine the Avogadro constant by using the x-ray crystal density method. In this work, to investigate surface characteristics of Si spheres both in vacuum and in air, a new ellipsometer having a vacuum chamber was developed. This ellipsometer enables accurate determination of the density of ²⁸Si-enriched spheres.