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This paper reports how the spectral linewidths of plasmon resonances can be narrowed down to a few nanometers by optimizing the morphology, surface roughness, and crystallinity of metal nanoparticles (NPs) in two-dimensional (2D) lattices. We developed thermal annealing procedures to achieve ultranarrow surface lattice resonances (SLRs) with full-width at half-maxima linewidths as narrow as 4 nm from arrays of Au, Ag, Al, and Cu NPs. Besides annealing, we developed a chemical vapor deposition process to use Cu NPs as catalytic substrates for graphene growth. Graphene-encapsulated Cu NPs showed the narrowest SLR linewidths (2 nm) and were stable for months. These ultranarrow SLR nanocavity modes supported even narrower lasing emission spectra and high nonlinearity in the input–output light–light curves.

Understanding the energetics of adhesion between two-dimensional nanomaterials and their supporting substrates is crucial for the design and fabrication of corrersponding structures with controlled interfacial effects that influence phononics, charge-carrier distribution, and electronic response. Here, we show a mechanical energy model that equates the adhesion energy of MoS on rigid and flat substrates (SiO and SiN) to the attributes of a single wrinkle in a MoS flake. The amplitude of the observed wrinkles was normalized for thickness (A/t) to select the wrinkles valid for the model. The adhesion energy values of 0.170 ± 0.033 J m for MoS on SiO and 0.252 ± 0.041 J m for MoS on SiN were determined. This mechanical energy model is consistent with the model based on the local equilibrium at the contact point in the Young's equation. We also propose a method to measure the plane-strain in wrinkled MoS. The geometrical properties (symmetry and normalized dimensions) of wrinkles and substrate effects are also discussed.