Cluster deposition techniques

The size of the deposit depends on the size of the hole and not on polarization time, denoting a certain balance between electrochemical energy and the surface energy of the cluster. This technique has been also employed to study the filling of Au cavities by Bi and Ag. In the latter work, the behavior of Bi is contrasted with that of Ag. While the holes are filled at underpotentials in the first... 

Palladium clusters deposited on amorphous carbon have been studied by XPS and UPS [28] and both techniques show broadening of the d-band peak as cluster size increases. The d-threshold shifts towards Ep as cluster size increases. In UPS studies the d-emission of the single atom has its peak at 3.0 eV below Ep, whereas the d-threshold is 2eV below Ep. Palladium clusters evaporated onto Si02 have been studied by UPS [38]. At large coverages of the Pd metal evaporated (> 10 atoms/cm ), a high emission intensity at Ep excited with photons of 21.2 eV (He(I)) or 40.8 eV (He(II)) as excitation source, is observed. This feature is characteristic in the spectra from bulk Pd samples. At the lowest metal coverage (3 x 10 atoms/cm ),... 

The talk will briefly review some of these developments ranging from high temperature equilibrium plasmas to cool plasmas, PECVD, ion implantation, ion beam mixing and ion assisted etching and deposition. Brief consideration will also be given to sputtering and ionised cluster beam deposition techniques in inorganic synthesis. 

CoO-coated Co cluster and oxide-coated Fe cluster assemblies were prepared by a plasma-gas-aggregation cluster-beam-deposition technique [37-39]. For preparation of CoO-coated Co cluster assembly, oxygen gas was introduced through a nozzle near the skimmer into the deposition chamber. The Co clusters with CoO shells were formed before deposition onto the substrate [37], Figure 8 shows a TEM image of the clusters produced at oxygen gas flow rate R(02) = 1 seem. Clusters are almost monodispersed, with the mean diameter of about 13 nm. Electron diffraction pattern indicated the coexistence of Co and CoO phases. The cluster assemblies were formed on a polyimide film with a thickness of about 100 nm. 

Figure 17 gives two examples of cluster film structure (a) clusters are embedded in matrix by co-deposition or, (b) isolated by a matrix via multilayering. The ability of the deposition technique to independently control these parameters makes it ideal for systematic studies of magnetic clusters. In this section, some recent work on FePt Ag and FePt C cluster films from our laboratory are reviewed. 

Nanoparticle systems can be prepared by various deposition techniques (sputtering, cluster deposition) and in particular, serve as model systems to study magnetisation processes at the nanoscale. In addition, the magnetic... 

The synthesis of large clusters such as [A Ris]3- (Chapters 2 and 3) proceeds by A1 atom cluster-core build up. Cluster-core growth is terminated at some point by external ligands. The method of Schnockel is a variation of metal-atom vapor-deposition techniques and relies on (a) the reversibility of the equilibrium between the liquid metal, e.g., Al, and gaseous metal halide, e.g., AICI3, with gaseous subhalide, e.g., A1C1 (b) the shift in equilibrium position with temperature and (c) competitive rates at similar temperatures of subhalide disproportionation to metal... 

This technique gives atomically flat facets on the surface of the sphere. STM scans of the substrates before cluster deposition showed them to be free from any debris that resembled clusters. After deposition the Au clusters were found uniformly distributed on the flat facets of Au substrates but only at steps on the Pt surface. 

The ordered P AA back-side and structured Al surface were used to produce self-organized metal nanoparticles. We used Au or amorphous carbon as add-layer for deposition of Ti or Fe nanostmctures. Both these metals have a weak wetting of the add-layer. The deposition was performed by a laser induced plasma deposition technique. In this process the energy of ions was about 20 eV. The highly ordered curved substrate surface defined position of the deposited clusters providing formation of highly ordered arrays of metal nanoclusters. A perspective application of such structures for terabit memory was demonstrated. For example, Ti nanoclusters covered by native oxide demonstrated irreversible transformation of I-V characteristics from barrier-like to the ohmic behavior after the action of current supplied by a tip of conductive AFM. 

Abstract Hybrid metal/metal oxide-poly-/>ara-xylylene (PPX) nanocomposites have attracted great interest, because of a broad spectrum of applications. A simple, low-cost preparation technique has been developed and comprises a cold-wall vacuum co-deposition technique. This co-deposition technique has been applied to synthesize nanocomposites, containing PPX and nanoparticles of Al, Sn, Zn, Ti and their oxides. Important is the oxidation kinetics of the metal clusters to their oxides in relation to the percolation threshold. 

In addition to its role as a surface analytical technique, STM has proven to be a unique tool for the synthesis of novel structures ranging from cluster deposition to positioning of single atoms. In vacuum studies, tip-sample interactions have generally been attributed to the influence of atomic forces, the electric field and/or the tunneling current [99]. In addition to these physical interactions, the tip may also be used to alter the local electrochemical conditions within the tunnel junction. Three... 

Several techniques have been applied for the production of preformed clusters in the gas phase, prior to their deposition onto a substrate. The low-energy cluster beam deposition technique was developed especially for the deposition of small clusters of transition metals (Ni, Fe, Co, etc.) [3.152]. An extensive review of this vast subject can be found in [3.153]. 

Beckel et al. [8] summarized thin-film deposition techniques in a slightly different grouping clustering the techniques mainly under vacuum deposition and liquid precursor-based thin-film deposition, and mentioned some interesting methods that were not included by Menzler et al. [7], such as polymeric precursors and impregnation. Table 10.3 gives their deposition method groupings. 

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