Thickness-dependent spontaneous dewetting morphology of ultrathin Ag films

Abstract

We show here that the morphological pathway of spontaneous dewetting of ultrathin Ag films on SiO 2 under nanosecond laser melting is found to be film thickness dependent. For films with thickness h between 2 ≤ h ≤ 9.5 nm, the morphology during the intermediate stages of dewetting consisted of bicontinuous structures. For films 11.5 ≤ h ≤ 20 nm, the intermediate stages consisted of regularly-sized holes. Measurement of the characteristic length scales for different stages of dewetting as a function of film thickness showed a systematic increase, which is consistent with the spinodal dewetting instability over the entire thickness range investigated. This change in morphology with thickness is consistent with observations made previously for polymer films [A. Sharma et al, Phys. Rev. Lett., v81, pp3463 (1998); R. Seemann et al, J. Phys. Cond. Matt., v13, pp4925, (2001)]. Based on the behavior of free * Corresponding author, ramki@utk.edu 1 energy curvature that incorporates intermolecular forces, we have estimated the morphological transition thickness for the intermolecular forces for Ag on SiO 2 . The theory predictions agree well with observations for Ag. These results show that it is possible to form a variety of complex Ag nanomorphologies in a consistent manner, which could be useful in optical applications of Ag surfaces, such as in surface enhanced Raman sensing.

Formation and morphological evolution of self-similar 3D nanostructures on weakly interacting substrates

“…Currently, the most detailed atomistic * kostas.sarakinos@liu.se description of far-from-equilibrium 3D island formation is based on homoepitaxial systems in which 3D islands (mounds) form by deposition onto existing small islands, followed by atomic-step descent limited by the Ehlrich-Schwöbel barrier [15][16][17][18][19]. However, for weakly interacting film/substrate systems-including Ag/SiO 2 [20][21][22][23][24], Pd/TiO 2 [25], Cu/ZnO [26,27], and Dy/graphene [4,28]-3D islands develop before the initially formed one-atom-high islands are large enough to efficiently capture vapor-phase deposition flux. Moreover, 3D island formation is also known to occur in the absence of deposition flux due to surface restructuring via dewetting [29].…”

Transparent electrode of nanoscale metal film for optoelectronic devices

“…76 This dewetting tendency of pure Ag becomes more obvious at elevated temperatures. 57,77 Zhang et al 48 and Gu et al 49 used Al doping to fabricating ultrathin (3 nm) Ag-based thin films with high thermal stability on SiO 2 ∕Si (100) substrates. Al doping yielded smaller and denser nuclei [ Fig.…”

Morphology transitions in bilayer spinodal dewetting systems

“…Irradiation was at normal incidence with an unfocused laser beam of area 1 × 1 mm 2 at a repetition rate of 50 Hz. The laser energy density was typically between 80 to 100 mJ/cm 2 , and chosen such that the entire bilayer could be melted for all the thickness combinations, as evidenced by a visible morphology change 17,30 . The morphology was studied as a function of the individual and combined film thickness of the bi-layer systems.…”

“…The underlying physical reasoning for this behavior is attributed to the role of the free energy curvature in the dynamical equations that determine the transport of matter, much like the case of spinodal phase segregating systems 14 . While the general validity of this observation has been verified in single-layer polymer 15,16 and metal films 17,18 , its applicability to describing the behavior of more complex bi-layer films or higher order spinodal dewetting systems, has not been evaluated thus far.…”