Radial Structure of Free Yb/YbO Nanoparticles Created by Oxidation Before or After Aggregation with Divalent Instead of Trivalent Oxide

Abstract

Nanoparticles consisting of Yb and its divalent oxide YbO have been created by two different oxidation approaches based on the gas-aggregation method with magnetron sputtering. In one type of nanoparticles, the Yb oxide molecules, created by reactive sputtering before the aggregation, agglomerate predominantly in the interior of mixed-composition nanoparticles. In the other type, the oxide is formed by exposing the preformed metallic Yb nanoparticles to oxygen, which at certain conditions is believed to oxidize primarily the surface of such nanoparticles. Such segregated stoichiometry has been disclosed using Yb 4f core-level photoelectron spectroscopy at a series of oxidation conditions for each type of production. In contrast to a typical macroscopic case where Yb is trivalent, in both production cases, Yb is divalent in the oxide. By using the production methods suggested, it becomes possible to tailor the electronic and thus the physical and chemical properties of such nanoparticles, which are discussed in the literature as building blocks for photonic, electronic, and magnetic nanoscale devices.