Monodisperse nanoparticles via metal induced crystallization

This paper discusses the self-assembled formation of monodisperse gold-rich nanoparticles and associated crystalline silicon nanostructures. Multilayer films comprising of amorphous Au25Si75 and amorphous silicon were grown via dc magnetron sputtering and subsequently annealed under varying thermal conditions. The films were characterized by electron microscopy before and after the thermal anneal. Thermal decomposition of the multilayer films results in the metal induced crystallization of amorphous silicon, as well as the formation of uniform Au-rich nanoparticles. Further annealing did not alter the size or position of the nanoparticles, indicating that the particles are too small to induce further silicon crystallization. Through thermodynamic modeling, two mechanisms are shown to be viable means for nanoscaled size selection. The first mechanism entails crystallization of Au25Si75 followed by metal induced crystallization of amorphous silicon, while the second utilizes spinodal decomposition of Au25Si75 to select a single nanoparticle radius.