Formation Mechanism of Well-Ordered Densely Packed Nanoparticle Superlattices Deposited from Gas Phase on Template-Free Surfaces
Abstract Superlattices of nanoparticles are generally produced based on solution chemistry processes. In this paper, we demonstrate that self-assembled monolayer structures of nanoparticles with superlattice periodicities can also be produced on template-free surfaces in the gas phase cluster beam deposition process. It is found the packing of Fe nanoparticles corresponds to an average two-dimensional densely-packed lattice with a hexagonal summary. By controlling the nanoparticle coverage, the two-dimensional densely-packed monolayer morphology can spread to the whole substrate surface being deposited. A formation mechanism of the ordered monolayers is proposed by considering the balance between the diffusion rate of the nanoparticles and their filling speed on the substrate surface determined by the deposition rate, and the ordering driven by the inter-particle attractive forces. The model is strongly supported by a serial of carefully designed cluster deposition experiments.