Synthesis of yttrium clusters

Abstract

We report on the synthesis of Y nanoclusters and a particular chemical solid-state reaction of these clusters YH 2⇔YH 3, which has recently received increasing interest in the case of continuous thin films. We used a novel type of laser ablation cluster source to synthesize Y-clusters of about 25–30 nm average size at different Ar background gas pressures to hydrogenize them in situ. The clusters were characterized by electron microscopy and optical spectroscopy. It was found that clusters prepared in higher Ar gas pressure consist of Y-core and Y 2O 3-shell contrary to Y-clusters synthesized at low Ar gas conditions. Analysis of corresponding extinction spectra were made by Mie theory calculations. Reaction with hydrogen was observed only for deposited Y-clusters which were hydrogenated at room temperature by adding atomic H. In a first step the metallic dihydride (YH 2) is formed. In a second step, additional H can form YH 3− x ( x<1 to x⪡1). The latter compound is electrically isolating. The fascinating properties of the last reaction are its reversibility at room temperature and the combination of a structural phase transition and a metal/non-metal transition. The reversible phase transition was monitored by the optical spectra which exhibit several strong and selective Mie resonances.