We experimentally investigate the flow of hydrolyzed polyacrylamide (HPAM) solution with and without salt in model porous media at high Weissenberg numbers (Wi > 1.0). The effect of pore shapes on the flow pattern and pressure drop is explored by using periodic arrays of circular and square pillars in aligned and staggered layouts. In the apparent shear-thinning regime, we observe stationary dead zones upstream of the pillars. In addition, we confirm that the size of stationary dead zones correlates with the level of shear-thinning, by varying the amount of salt in HPAM solution. At higher shear rates (or Wi), these dead zones are periodically washed away. We present the mechanism of this elastic instability and characterize it based on the pressure drop fluctuation spectral density.

consisting of two or more alternating self-limiting surface reactions. These selflimiting surface reactions enable thin-film deposition with thickness uniformity over large-area substrates, (sub-) monolayer thickness control, and conformal deposition in 3D structures. [1] During the first ALD cycles the precursors mainly react with the substrate rather than with the ALD-grown material. The surface termination of the substrate can therefore strongly affect the growth behavior during this initial period. [1][2][3] Depending on the nature of the ALD-grown material, the substrate, and the process conditions, ALD can lead to different growth regimes, resulting, for instance, in the deposition of ultrathin continuous films, deposition of highly dispersed nanoparticles, or area-selective deposition. [4] Continuous thin films have a wide variety of applications including nanoelectronics, coatings, and optical components, and their deposition requires either 2D growth or high particle density to achieve fast film closure. Nanoparticles dispersed on a surface are desired for heterogeneous catalysis, and their production requires island-type deposition with a well-defined particle size and particle density. Area-selective deposition can enable nanoscale bottom-up patterning, which allows accurate self-alignment between small features which is difficult to achieve in conventional top-down patterning. [5] To enable area-selective deposition, the growth behavior should be surface-dependent such that the deposition is at the same time favored on designated areas of the substrate and inhibited on others. For each of the aforementioned applications, an understanding of the surface dependence of the initial stages of growth can inform the tailoring of the ALD process to the desired application. [6] ALD of noble metals has received considerable attention because of its potential in applications such as catalysis [7] and nanoelectronic devices. [8] Ruthenium is considered an ideal candidate for novel nanoscale catalysts [9,10] as well as for replacing copper as a conductor in future low-level nano-interconnect structures for integrated circuits. [8] ALD of Ru however presents application-specific challenges. On one hand, nanoparticles of a specific size are desired for high catalytic activity. [10] On Understanding the growth mechanisms during the early stages of atomic layer deposition (ALD) is of interest for several applications including thin film deposition, catalysis, and area-selective deposition. The surface dependence and growth mechanism of (ethylbenzyl)(1-ethyl-1,4-cyclohexadienyl) ruthenium and O 2 ALD at 325 °C on HfO 2 , Al 2 O 3 , OH, and SiOSi terminated SiO 2 , and organosilicate glass (OSG) are investigated. The experimental results show that precursor adsorption is strongly affected by the surface termination of the dielectric, and proceeds most rapidly on OH terminated dielectrics, followed by SiOSi and finally SiCH 3 terminated dielectrics. The initial stages of growth are characterized by the formation a...

Area-selective deposition (ASD) enables the growth of materials on target regions of patterned substrates for applications in fields ranging from microelectronics to catalysis. Selectivity is often achieved through surface modifications aimed at suppressing or promoting the adsorption of precursor molecules. Here, we show instead that varying the surface composition can enable ASD by affecting surface diffusion rather than adsorption. Ru deposition from (carbonyl)-(alkylcyclohexadienyl)Ru and H 2 produces smooth films on metal nitrides, and nanoparticles on SiO 2 . The latter form by surface diffusion and aggregation of Ru adspecies. Kinetic modeling shows that changing the surface termination of SiO 2 from −OH to −CH 3 , and thus its surface energy, leads to larger and fewer nanoparticles because of a 1000fold increase in surface diffusion rates. Kinetic Monte Carlo simulations show that even surface diffusion alone can enable ASD because adspecies tend to migrate from high-to low-diffusivity regions. This is corroborated by deposition experiments on threedimensional (3D) TiN−SiO 2 nanopatterns, which are consistent with Ru migrating from SiO 2 to TiN. Such insights not only have implications for the interpretation of experimental results but may also inform new ASD protocols, based on chemical vapor and atomic layer deposition, that take advantage of surface diffusion.

<div> <div> <p>Area-selective deposition (ASD) enables the growth of materials on target regions of patterned substrates for applications in fields ranging from microelectronics to catalysis. Selectivity is often achieved through surface modifications aimed at suppressing or promoting the adsorption of precursor molecules. Here we show, instead, that varying the surface composition can enable ASD by affecting surface diffusion rather than adsorption. Ru deposition from (carbonyl)- (alkylcyclohexadienyl)Ru and H₂ produces smooth films on metal nitrides and nanoparticles on SiO₂. The latter form by surface diffusion and aggregation of Ru adspecies. Kinetic modeling shows that changing the surface termination of SiO₂ from -OH to -CH₃, and thus its surface energy, leads to larger and fewer nanoparticles because of a 1000-fold increase in surface diffusion rates. Kinetic Monte Carlo simulations show that even surface diffusion alone can enable ASD because adspecies tend to migrate from high- to low-diffusivity regions. This is corroborated by deposition experiments on 3D TiN-SiO₂ nanopatterns, which are consistent with Ru migrating from SiO₂ to TiN. Such insights not only have implications for the interpretation of experimental results but may also inform new ASD protocols, based on chemical vapor and atomic layer deposition, that take advantage of surface diffusion.</p></div></div>