Scaling of elongation transition thickness during thin-film growth on weakly interacting substrates

Abstract

The elongation transition thickness (hElong) is a central concept in the theoretical description of thin-film growth dynamics on weakly interacting substrates via scaling relations of hElong with respect to rates of key atomistic film-forming processes. To date, these scaling laws have only been confirmed quantitatively by simulations, while experimental proof has been left ambiguous as it has not been possible to measure hElong. Here, we present a method for determining experimentally hElong for Ag films growing on amorphous SiO2: an archetypical weakly interacting film/substrate system. Our results confirm the theoretically predicted hElong scaling behavior, which then allow us to calculate the rates of adatom diffusion and island coalescence completion, in good agreement with the literature. The methodology presented herein casts the foundation for studying growth dynamics and cataloging atomistic-process rates for a wide range of weakly interacting film/substrate systems. This may provide insights into directed growth of metal films with a well-controlled morphology and interfacial structure on 2D crystals-including graphene and MoS2-for catalytic and nanoelectronic applications. Published by AIP Publishing.<p>Funding Agencies|Linkoping University (LiU) [Dnr-LiU-2015-01510]; Swedish research council [VR-2011-5312, VR-2015-04630]; Swedish National Infrastructure for Computing (SNIC) at the National Supercomputer Centre (NSC)</p

Coalescence dynamics of 3D islands on weakly-interacting substrates

“…The fact that Q/Q 0 ≤ 1 for F ≤ 0.5 ML/s means that the coalescing cluster contracts upon reshaping; this is because atoms that are initially in contact with the substrate are redistributed on the sidewall facets when island (2) is absorbed by island (1). The cluster contraction is consistent with the experimentally-observed island area depletion during film growth on weakly-interacting substrates at conditions which favor island coalescence 12,13 and lead to a pronounced 3D morphology and surface roughness built up 2,[12][13][14][15][16][17][18]27 . Conversely, the Q/Q 0 values in Fig.…”

“…Our findings explain experimental results which show a transition from 3D to 2D film growth morphology on weakly-interacting substrates when rate of coalescence is suppressed, as well as the origin of changes in thin www.nature.com/scientificreports www.nature.com/scientificreports/ film roughness and grain boundary number densities when varying the magnitude of vapor flux arrival rate 2,[12][13][14][15][16][17][18] . In addition, our results point out that disagreement between theoretical works predicting different scaling behavior for the percolation transition thickness than that observed experimentally might be due to the effect of deposition rate in the coalescence of island pairs.…”

“…Combining this scaling dependency with the droplet growth theory 13,29 , Carrey and Maurice 30,31 showed that the nominal film thickness at which a film that grows in 3D fashion (e.g., during metal film deposition on weakly-interacting substrates) reaches percolation θ perc scales with the vapor arrival rate as θ perc~ F −1/3 . Experimentally, the scaling law θ perc ~ F −1/3 is only partially validated with reported scaling exponents ranging between −0.33 and −0.25 12,14,17,27 . It has been suggested that the disparity between experiments and theory is the result of islands being faceted, which leads to equilibration times scaling as ~ R a , with a > 0.…”

“…www.nature.com/scientificreports www.nature.com/scientificreports/ dynamics may be relevant for understanding disparities between experimental data for the scaling behavior of the percolation transition thickness during film growth on weakly-interacting substrates and predictions based on the sintering and droplet growth theories 2,6,[10][11][12][13][14][15][16][17][18] . The overall results of this study provide insights for enabling controlled growth of metal films and supported nanostructures on weakly-interacting substrates 19 , including oxides and 2D materials, which is a key step in fabrication of high-performance nanoelectronic, optoelectronic, catalytic and sensing devices 5,[20][21][22] .…”

Thin metal films on weakly-interacting substrates : Nanoscale growth dynamics, stress generation, and morphology manipulation

“…[48][49][50] While is readily obtainable in simulations (i.e., thickness at which the average island cluster consists of two islands), experimental determination is difficult, as it does not have implications to measurable physical properties. While visual observation of film surfaces close to , e.g., with scanning tunnel microscopy, [51,52] is one option to study this transition, an indirect approach has been proposed by Lü et al, [53] who determine by changing the adatom arrival rate during deposition and thus activating/freezing island coalescence.…”