Preventing Thin Film Dewetting via Graphene Capping

Abstract

A monolayer 2D capping layer with high Young's modulus is shown to be able to effectively suppress the dewetting of underlying thin films of small organic semiconductor molecule, polymer, and polycrystalline metal, respectively. To verify the universality of this capping layer approach, the dewetting experiments are performed for single-layer graphene transferred onto polystyrene (PS), semiconducting thienoazacoronene (EH-TAC), gold, and also MoS on PS. Thermodynamic modeling indicates that the exceptionally high Young's modulus and surface conformity of 2D capping layers such as graphene and MoS substantially suppress surface fluctuations and thus dewetting. As long as the uncovered area is smaller than the fluctuation wavelength of the thin film in a dewetting process via spinodal decomposition, the dewetting should be suppressed. The 2D monolayer-capping approach opens up exciting new possibilities to enhance the thermal stability and expands the processing parameters for thin film materials without significantly altering their physical properties.

Enabling remote quantum emission in 2D semiconductors via porous metallic networks

“…Unlike the full prevention of Au dewetting reported by Cao et al, 24 we find reduced dewetting under the graphene resulting in metal pores (dark regions, Fig. 1d) that range in diameter from approximately 100-1000 nm depending on annealing conditions.…”

“…In this example, a narrow exfoliated strip of few-layer graphene was deposited on a 25 nm thick Au film and the sample was annealed at 350 C for 30 min. As thermodynamic modeling suggests, 24 Au film dewetting is impeded beneath the graphene layer as compared with the Au-only region.…”

“…As mentioned earlier, the competing forces at play are the differences in surface energy between the metal and the substrate, and the metal and the 2DC layer, as well as the high Young's modulus of the 2DC, which reduces surface fluctuations that initiate dewetting. 24 Without the 2DC overlayer, the Au film completely dewets to form localized Au islands with randomly orientated in-plane crystal directions.…”

“…23 Despite being atomically thin, 2D materials significantly modify metal film dewetting due to their relatively high Young's Modulus, which suppresses surface fluctuations. 24 We show here that under appropriate annealing conditions, the metal underlayer becomes highly textured and in crystallographic alignment with the 2DC overlayer, analogous to a 'reverse epitaxy' process (or surface-templated epitaxy). As dewetting initiates, pores form in the metal film while the 2DC overlayer either remains suspended above or coats the inside of the pores.…”

Ag Thin Film Dewetting Prevention by Ion Implantation

“…Thin film processing tends to be restricted by interface dewetting due to unstable interfacial energy between film surface and matrix . Conventional methods in dewetting prevention emphasize on 1) intercalating new chemical species at film–matrix interface to minimize the interfacial energy and 2) depositing capping layers with superior mechanical strength upon original film to suppress its fluctuation and to enhance surface conformity . In other words, antidewetting is achieved either by chemical interfacial modification or by mechanical surface reinforcement.…”