Coalescence dynamics of size-selected gold clusters studied by time-resolved transmission electron microscopy

Abstract

Abstract. Coalescence dynamics of size-selected gold (Au) clusters (each with nominal 923 atoms), on amorphous Si 3 N 4 substrate at room temperature, has been studied via time-resolved transmission electron microscopy (TEM). We found that the clusters approached each other in two stages. In the first stage, the drift velocity was independent of the particle separation and could be attributed to beam-induced random motion. In the second stage, the clusters were found to jump into contact with a much higher final averaged speed. This is independent of beam dose rates and is attributed to the van der Waal attraction. IntroductionCoalescence of supported metal nanoparticles/clusters is a common phenomenon in the field of catalysis, whose process is known to relate to many factors, such as size, structure, orientation, temperature, support and environment [1,2]. It is critical to quantify these factors for understanding the physical mechanism of the coalescence if one wants to rationally design a catalyst system. Previous experimental studies of nanoparticle coalescence are mainly on particles of different sizes [1,3], thus it is difficult to differentiate the effect of size as to other factors such as temperature, structure, etc. Here we utilised the unique capability of an atomically size-controlled cluster source in our group, together with a fast acquisition feature of a microscope camera, to study the coalescence phenomena between gold (Au) clusters. Specifically, we reported the effects of the cluster size and electron dose on the coalescence of Au clusters.

Oxidation behavior and atomic structural transition of size-selected coalescence-resistant tantalum nanoclusters

“…Additionally, the sintering behavior of clusters at elevated temperatures is interesting from a fundamental perspective and coalescence of clusters serves as a promising starting point for investigating film structure. There have been some MD studies investigating the coalescence of various clusters [41][42][43], which consistently produced similar or complementary findings regarding the physical processes involved in cluster sintering. The primary driving force behind this phenomenon is identified as the minimization of surface energy, followed by atomic diffusion.…”