Coalescence aspects of cobalt nanoparticles during in situ high-temperature annealing

Abstract

Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. In this work we investigate the coalescence aspects of Co nanoparticles. It was observed that nanoparticles in contact with the substrate are relatively immobile, whereas those on top of other Co particles can rearrange themselves during high-temperature annealing and further coalesce. Indeed, similar size particles prior to coalescence come at close proximity forming an arc-shaped area, which leads to finite-size necking and thereafter to coalescence towards a single partially spherical particle. This is in contrast to the theoretical predictions where necking occurs following an initial pathway of a point contact. Moreover, it was shown that after necking a transient period of relatively fast coalescence occurs followed by a slower coalescence rate at constant speed towards a single particle with partial spherical shape. In addition, the coalescence is faster with decreasing particle size, where in the case of unequal size the smallest particle is mainly absorbed by an adjacent large one in an Ostwald ripening process.

Quantitative analysis for in situ sintering of 3% yttria-stablized zirconia in the transmission electron microscope

“…Rankin et al have monitored zirconia nanoparticles during in situ heating and observed particle reorientation and neck growth [8,9]. Direct observations of coalescing particles have also been used to calculate the maximum distance between particles and their displacement during sintering [7,10].…”

Effect of island coalescence on structural and electrical properties of InN thin films

“…1). This shape occurs since it leads to surface energy minimization for nuclei formed at equilibrium, and because of kinetics where the shape is determined by the rate at which different crystal faces grow [21]. However, the combination of factors such as temperature, kinetics, impurities, and surface energy effects could lead to unusual nanoparticle size-shape distributions, which influences the particle coalescence.…”

“…On the other side, observed flat-top InN pyramids indicate a significant lateral growth rate. Such a shape favours a rapid coalescence and a flatter morphology of the thicker films [21]. The presented estimations, however, assume a serious simplification of the real processes.…”

“…Adatoms diffuse on the island surface from the regions of high curvature (fewer neighbours and therefore less strongly bound) towards the regions of lower curvature (e.g. facets) providing lateral growth of the initial nuclei [21]. Macroscopic theories of coalescence via atomic surface diffusion predict a coalescence time [22]:…”

“…The presence of various structural features (i.e. steps, kinks, and facets) [20,23] and Ostwald ripening [21,24] has to be taken into account.…”