Ordered Ag nanocluster structures by vapor deposition on pre-patterned SiO₂

Abstract

Highly ordered Ag nanocluster structures have been grown on pre-patterned amorphous SiO(2) surfaces by oblique angle physical vapor deposition at room temperature. Despite the small undulation of the rippled surface, the stripe-like Ag nanoclusters are very pronounced, reproducible and well separated. Computer modeling of the growth has been performed with a lattice-based kinetic Monte Carlo (KMC) method using a combination of a simplified inter-atomic potential and experimental transition barriers taken from the literature. An effective transition event classification method is introduced which allows a boost factor of several thousand compared to a traditional KMC approach, thus allowing experimental time scales to be modeled. The simulation predicts a low sticking probability for the arriving atoms, millisecond order lifetimes for single Ag adatoms and ≈1 nm square surface migration ranges of Ag adatoms. It is also shown that metal nucleations can trigger even on defect free surfaces. The simulations give excellent reproduction of the experimentally observed nanocluster growth patterns.

Sub-monolayer growth of Ag on flat and nanorippled SiO2 surfaces

“…We chose two sets of parameters that gave average binding energies of 0.2 and 0.6 eV. The former value is consistent with previous lattice-based KMC simulations 8 .…”

“…Recently, studies were undertaken using lattice-based Kinetic Monte Carlo (KMC) to model the growth of Ag nanoparticles on a rippled SiO 2 surface 8 . The model used simplified assumptions such as no reflection of Ag, no cluster migration and no energy nor angle of incidence dependence of the incident Ag 8,9 . In addition the underlying lattice was assumed to be face-centred cubic (fcc) so it was not clear if the predicted growth patterns were affected by this.…”

Thermal dynamics of silver clusters grown on rippled silica surfaces

“…References 13 and 14 consider the ripening process in detail after the deposition of individual atoms whereas reference 15 investigates the impact of clusters themselves onto a surface. Only few studies have focussed to understand the atomic interaction of silver with silica [16][17][18] . In a previous paper 19 we parametrised an interatomic potential function for the Ag-SiO 2 interaction, based on matching sticking probabilities to Rutherford backscattering data.…”

“…Recently, a study based on the Kinetic Monte Carlo (KMC) method was undertaken to understand the mechanisms of the growth of silver nanoparticles on the patterned surfaces 17 . The reported study has limitations in some of the assumptions of the model such as no reflection of the Ag atom from the surface and no cluster migration on the surface.…”

“…The reported study has limitations in some of the assumptions of the model such as no reflection of the Ag atom from the surface and no cluster migration on the surface. In addition, the energy and the angle of incidence (AOI) of the incoming atom were not parameters of the model 17 .…”