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 nano-scale 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 new class of ligand called N-heterocyclic carbenes (NHCs). 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 novel 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. It offers a promising avenue for subnanometer smoothing in microfabrication workflows. Our observations pave the way for atomic layer restructuring (ALR), a technique that compliments atomic layer deposition (ALD) and atomic layer etching (ALE) in the fabrication and processing high precision materials.