Atomic Layer Restructuring of Gold Surfaces by N-Heterocyclic Carbenes over Large Surface Areas

Even highly planar, polished metal surfaces display varying levels of roughness that can affect their optical and electronic properties, impacting performance in state-of-the-art microelectronics. Current methods for smoothing rough metallic surfaces require either the removal or addition of substantial amounts of material using complex processes that are incompatible with 3-dimensional nanoscale features needed for state-of-the-art applications. We present a vapor-phase process that results in up to a 60% smoothing of nanometer-scale rough gold surfaces through a single exposure to a class of ligands called N-heterocyclic carbenes. This process does not require removal or addition of metal from the surface and provides smoothing at the Ångström scale. Smoothing occurs in a single deposition, giving quantifiable differences in the adsorption behavior of the resulting surfaces. The process takes place through an adatom-extraction-driven destabilization and restructuring of the surface in a self-limiting manner. This process is achieved without the use of harsh chemical etchants or mechanical intervention, takes only minutes, and can easily be integrated with vapor-phase processing in situ in microfabrication workflows. Our observations demonstrate atomic layer restructuring, a technique that compliments atomic layer deposition and atomic layer etching in the fabrication and processing of high-precision materials.