Atomic-scale diffusion rates during growth of thin metal films on weakly-interacting substrates

Abstract

We use a combined experimental and theoretical approach to study the rates of surface diffusion processes that govern early stages of thin Ag and Cu film morphological evolution on weakly-interacting amorphous carbon substrates. Films are deposited by magnetron sputtering, at temperatures T S between 298 and 413 K , and vapor arrival rates F in the range 0.08 to 5.38 monolayers / s . By employing in situ and real-time sheet-resistance and wafer-curvature measurements, we determine the nominal film thickness Θ at percolation (Θ perc ) and continuous film formation (Θ cont ) transition. Subsequently, we use the scaling behavior of Θ perc and Θ cont as a function of F and T s , to estimate, experimentally, the temperature-dependent diffusivity on the substrate surface, from which we calculate Ag and Cu surface migration energy barriers and attempt frequencies . By critically comparing and with literature data, as well as with results from our ab initio molecular dynamics simulations for single Ag and Cu adatom diffusion on graphite surfaces, we suggest that: (i) and correspond to diffusion of multiatomic clusters, rather than to diffusion of monomers; and (ii) the mean size of mobile clusters during Ag growth is larger compared to that of Cu. The overall results of this work pave the way for studying growth dynamics in a wide range of technologically-relevant weakly-interacting film/substrate systems—including metals on 2D materials and oxides—which are building blocks in next-generation nanoelectronic, optoelectronic, and catalytic devices.

Manipulation of thin silver film growth on weakly interacting silicon dioxide substrates using oxygen as a surfactant

“…Multiple studies 42,49,[53][54][55][56] Ag-layer synthesis conditions, which is in very good agreement with the thicknesses obtained from spectroscopic ellipsometry. Moreover, ρ m is very close to the bulk Ag mass density (10.49 g/cm 3 ) 57 as expected for magnetron-sputter-deposited high mobility (i.e., low melting point) metal films 58,59 . We also find that w a-C Ag ⁄ = 1.8 nm for the Argrown film, while addition of O 2 to the sputtering atmosphere leads to w a-C Ag ⁄ =1.5 nm.…”

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.…”

“…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] .…”

Ultrathin sputter-deposited plasmonic silver nanostructures

“…The reported large diffusivity of Ag on various weakly interacting substrates supports this argument. 46,47 In any case, it seems that the silver growth on AZO is improved by the presence of the structure, making stable nanostructured Ag lms as thin as 6 nm possible. The formation of Ag grains on the side walls of the nanostructures was further investigated by change of the geometry of the nanostructured resist, prior to deposition of 10 nm AZO and 6 nm Ag.…”