Volmer-Weber growth stages of polycrystalline metal films probed by in situ and real-time optical diagnostics

Abstract

The Volmer-Weber growth of high-mobility metal films is associated with the development of a complex compressive-tensile-compressive stress behavior as the film deposition proceeds through nucleation of islands, coalescence, and formation of a continuous layer. The tensile force maximum has been attributed to the end of the islands coalescence stage, based on ex situ morphological observations. However, microstructural rearrangements are likely to occur in such films during post-deposition, somewhat biasing interpretations solely based on ex situ analysis. Here, by combining two simultaneous in situ and real-time optical sensing techniques, based on surface differential reflectance spectroscopy (SDRS) and change in wafer curvature probed by multibeam optical stress sensor (MOSS), we provide direct evidence that film continuity does coincide with tensile stress maximum during sputter deposition of a series of metal (Ag, Au, and Pd) films on amorphous SiOx. Stress relaxation after growth interruption was testified from MOSS, whose magnitude scaled with adatom mobility, while no change in SDRS signal could be revealed, ruling out possible changes of the surface roughness at the micron scale.

Localized surface plasmon resonance of Au/TiO2(110): substrate and size influence from in situ optical and structural investigation

“…A continuous gold lm would rather give rise to a signal continuously increasing with the wavelength. 32 The plasmonic signature is clearly detected at $2 ML, corresponding to a NPs size of about 2 nm. This result agrees with ab initio TDDFT calculations, showing that the coupling with interband (IB) transitions from the d electrons induces LSPR damping with size decreasing up to the point to disappear almost completely at about 2 nm.…”

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

“…[3] A characteristic tensile film force maximum is found for both cases (at ~10 for Fe and ~18 for Cu); the thickness of this tensile peak has been shown to correspond to the continuous film formation thickness ℎ . [101] The tensile stress forming for mean film thickness ℎ < ℎ corresponds to stress owing to island coalescence, while the compressive stress observed for ℎ > ℎ is associated with atomic-scale processes occurring in continuous layers. We note that the magnitude of tensile stress for ℎ < ℎ is identical for low and high mobility conditions (300 vs. 520 for Fe and 110 vs. 300 for Cu), which indicates that the island nucleation and coalescence stages are similar (i.e., island number densities, island sizes).…”

Investigation of large enhancement of spin hall angle in heterostructures of Ag nanoparticles randomly grown in Pt

“…The growth of Ag occurs by following the Volmer-Weber mode as shown in Figure 1 e). [21][22][23] This growth mode is characterized by the two-dimensional formation of 3D nanosized islands that further grow until reach the coalescence regime where it forms a continuous layer. Note that the sizes of Ag islands grown on top of the Pt layer are quite large.…”