文章基本信息

标题：Reduced GeO2 Nanoparticles: Electronic Structure of a Nominal GeOx Complex and Its Stability under H2 Annealing
本地全文：下载
作者：Jia Zhao ; Linju Yang ; John A. McLeod 等
期刊名称：Scientific Reports
电子版ISSN：2045-2322
出版年度：2015
卷号：5
期号：1
DOI：10.1038/srep17779
语种：English
出版社：Springer Nature
摘要：A nominal GeO_x (x ≤ 2) compound contains mixtures of Ge, Ge suboxides, and GeO₂, but the detailed composition and crystallinity could vary from material to material. In this study, we synthesize GeO_x nanoparticles by chemical reduction of GeO₂, and comparatively investigate the freshly prepared sample and the sample exposed to ambient conditions. Although both compounds are nominally GeO_x, they exhibit different X-ray diffraction patterns. X-ray absorption fine structure (XAFS) is utilized to analyse the detailed structure of GeO_x. We find that the two initial GeO_x compounds have entirely different compositions: the fresh GeO_x contains large amorphous Ge clusters connected by GeO_x, while after air exposure; the Ge clusters are replaced by a GeO₂-GeO_x composite. In addition, the two GeO_x products undergo different structural rearrangement under H₂ annealing, producing different intermediate phases before ultimately turning into metallic Ge. In the fresh GeO_x, the amorphous Ge remains stable, with the GeO_x being gradually reduced to Ge, leading to a final structure of crystalline Ge grains connected by GeO_x. The air-exposed GeO_x on the other hand, undergoes a GeO₂→GeO_x→Ge transition, in which H₂ induces the creation of oxygen vacancies at intermediate stage. A complete removal of oxides occurs at high temperature.