Sequential adsorption/deposition

Scanning probe microscopies are now able to study in situ the growth of metal clusters. These studies are performed sequentially after deposition. On metal/metal systems it has been possible to follow the nucleation kinetics and to derive the elementary energies like adsorption and diffusion energies (see the excellent review by Brune [68]). On oxide surfaces only recently such studies have been undertaken. STM can be only used on conducting samples, however it is possible to use as a support an ultrathin film of oxide grown on a metal. By this way it has been possible to study the nucleation of several... 

Prussian Blue was tentatively deposited onto isolated polycations by the well-known layer-by-layer (or multiple sequential adsorption) technique. The stepwise adsorption of hexacyanoferrate anions and ferric (or ferrous) cations was actually effective in fabricating PB films [12], In this work, the first adsorption step of hexacyanoferrate anions along positively charged PMB chains were successful as confirmed by the increase of the chain thickness by approximately 0.7 nm (Fig. la). 

Multilayer assemblies using monothiols are generally fragile. Multilayer deposition of nanocrystals is best achieved by the sequential adsorption of dithiol... 

FIGURE 15.6 Excluded interfacial area for deposition of molecules that adsorb according to the random sequential adsorption model. 

The polyelectrolyte multilayer films were prepared using the layer-by-layer (LbL) technique of electrostatically driven sequential adsorption of polyions from their solutions. The technique is described in details elsewhere [1,17]. Adsorption of polyelectrolytes was performed from solutions of NaCl in H2O of concentration 0.15 M at PE concentration of 0.5 g/1. Each deposition step lasted 20 min and rinsing in between the steps was done 3 times for 2 min in water. Always ultra pure water with Milli-Q quality was used. Ready samples were rinsed with D2O before the NR experiments. 

Figure 6 LbL deposition on particies by (a) centrifuge/redispersion steps, and (b) sequential adsorption, (c) Preliminary setup for continuous LbL assembly on gold nanoparticles by ultrafiltration.

Summary. The underpotential deposition (UPD) of metal sub-monolayers and monolayers on metal substrates for the systems Ag/Au(100), Au/Ag(100), Ag/Pt(100), Pt/Ag(100), Au/Pt(100), Pt/Au(100), Au/Pd(100), and Pd/Au(100) is studied by means of lattice Monte Carlo simulations. Interaction energies among different metal atoms are evaluated by using the embedded-atom method. A wide variety of physical situations are found and discussed, including systems exhibiting the sequential adsorption of atoms on kink and step sites, prior to the completion of the monolayer. On the other hand, for other systems, we observe the formation of 2D alloys... 

Successive Ionic Layer Adsorption and Reaction (SILAR) and Related Sequential Solution-Phase Deposition Techniques... 

Electrodeposition is by its nature a condensed phase process, whereas most studies of ALE have been performed using gas phase or vacuum methodologies, CVD or MBE. A solution phase deposition methodology related to ALE has been developed in France by Nicolau et al. [27-32] (Fig. 2), in which adsorbed layers of elements are formed by rinsing a substrate in aqueous solutions containing ionic precursor for the desired elements, sequentially, in a cycle. After exposure to each precursor, the substrate is copiously rinsed and then transferred to a solution containing the precursor for the next element. The method is referred to as successive ionic layer adsorption and reaction (SILAR). Reactivity in SILAR appears to be controlled by the rinsing procedure, solution composition, pH, and specifically... 

As pointed out earlier, CVD is a steady-state, but rarely equilibrium, process. It can thus be rate-limited by either mass transport (steps 2, 4, and 7) or chemical kinetics (steps 1 and 5 also steps 3 and 6, which can be described with kinetic-like expressions). What we seek from this model is an expression for the deposition rate, or growth rate of the thin film, on the substrate. The ideal deposition expression would be derived via analysis of all possible sequential and competing reactions in the reaction mechanism. This is typically not possible, however, due to the lack of activation or adsorption energies and preexponential factors. The most practical approach is to obtain deposition rate data as a function of deposition conditions such as temperature, concentration, and flow rate and fit these to suspected rate-limiting reactions. 

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