Nucleation and Growth of Recrystallized Grains in Supported Metal Nanoparticles

Abstract We employed solid state dewetting to fabricate faceted single crystalline Pt nanoparticles on sapphire substrates. The as-fabricated particles exhibited (111) out-of-plane orientations. The particles were compressed by a flat diamond wafer to various plastic strains and annealed at temperatures between 900 °C and 1000 °C. Plastic deformation caused a systematic drift of the out-of-plane orientation away from (111) toward (112) and (101) orientations. The grains with original (111) orientations re-appeared after annealing, and the microstructural evidence pointed at the nucleation of recrystallized grains at the center of deformed particles. Particles subjected to the highest strains developed multiple holes to the substrate near their edge after recrystallization. We discussed the nucleation of both recrystallized grains and annealing-induced holes in a unified framework that attributes these phenomena to non-equilibrium state of grain boundaries and the Pt-sapphire interface generated by plastic deformation and subsequent thermal annealing.