Formation and evolution of Au-SiOx Heterostructures: From nanoflowers to nanosprouts

• Published in: Materials & design Vol. 209; p. 109956
• Main Authors: Li, Feitao, Oliva-Ramírez, Manuel, Wang, Dong, Schaaf, Peter
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2021; Elsevier
• Subjects: Au silicide; Dewetting; Si active oxidation; SiO2 decomposition; Vapor–liquid–solid; SiO2 decomposition; Au silicide; Vapor–liquid–solid; Si active oxidation; Dewetting
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2021.109956

[Display omitted] •Novel sprout-like structure was produced by rapid annealing in a reducing atmosphere.•Two Si sources contribute to the formation of SiOx nanowires.•Volatile SiO moves to the surface by defect-mediated diffusing along the SiO2 layer.•Direction change of the main Si source relative to structures splits the particles. This work reports the formation of circular cavities and Au-SiOx nanoflowers after annealing of thin Au film deposited on SiO2/Si substrates, and the transformation of nanoflowers to nanosprouts with increasing the annealing time. Two reference experiments indicate that both H2 and Si are indispensable for the above structures. The formation of cavities can be attributed to the SiO2 layer decomposition and the product, volatile SiO, provides a Si source for the formation of nanoflowers at the early stage. A model is proposed to indicate that SiO gas produced at the Si/SiO2 interface can diffuse to the surface assisted by the defects in the SiO2 layer before the decomposed cavities are exposed. Then the exposing of those cavities introduces another volatile SiO from the active oxidation of Si substrate, provoking a change in the direction of the main Si source, which in turn makes the one nanoparticle of the nanoflower split in two and finally form the nanosprout. The model about the escape of SiO further details SiO2 decomposition process, and the transformation mechanism from nanoflowers to nanosprout sheds light on a feasible nanofabrication method to design tunable size and shape of nanoparticles.