Interfacial Fluctuations of a Nanoparticle Superlattice*

We use liquid-phase transmission electron microscopy to image and understand interfacial fluctuations of a nanoparticle superlattice. With single particle resolution and hundreds of nanoscale building blocks in view, we are able to identify a phase boundary between self-assembled ordered lattice and disordered structure and visualize the kinetics of lattice growth front. By applying the capillary wave theory towards this nanoscale interface, we found that this interface is roughened by thermal energy and we can extract the surface stiffness, fluctuation width and other quantities from real-space imaging. Our experimental results demonstrate the potential of extending model study on collective systems to nanoscale with liquid-phase TEM and also provide insight into formation process self-assembled nanoscale architectures.