Nanostructured film deposition

Baia, M., Baia, L., and Astilean, S. (2005) Gold nanostructured films deposited on polystyrene colloidal crystal templates for surface-enhanced Raman spectroscopy. Chemical Physics Letters, 404, 3-8. 

In order to take advantage of nanometer-sized semiconductor clusters, one must provide an electron pathway for conduction between the particles. This has been achieved by sintering colloidal solutions deposited on conductive glasses. The resulting material is a porous nanostructured film, like that shown in Fig. 1, which retains many of the characteristics of colloidal solutions, but is in a more manageable form and may be produced in a transparent state. Furthermore, the Fermi level within each semiconductor particle can be controlled potentiostati-cally, a feature which is fundamental for the functioning of the electrochromic devices described in Section III. 

Thin semiconductor films (and other nanostructured materials) are widely used in many applications and, especially, in microelectronics. Current technological trends toward ultimate miniaturization of microelectronic devices require films as thin as less than 5 nm, that is, containing only several atomic layers [1]. Experimental deposition methods have been described in detail in recent reviews [2-7]. Common thin-film deposition techniques are subdivided into two main categories physical deposition and chemical deposition. Physical deposition techniques, such as evaporation, molecular beam epitaxy, or sputtering, involve no chemical surface reactions. In chemical deposition techniques, such as chemical vapor deposition (CVD) and its most important version, atomic layer deposition (ALD), chemical precursors are used to obtain chemical substances or their components deposited on the surface. 

For free-clusters, the cluster size distribution can be measured by the time-of-flight mass spectrometer for cluster films deposited on substrate by the cluster beam, the measurement of size distribution and observation of nanostructure are mostly done using transmission electron microscopy (TEM). In this section we will focus on the latter and pay special attention to FePt, CoPt clusters which have high anisotropy Tl0 phase after annealing [43-45]. For the TEM observations, FePt, CoPt nanoclusters, produced in a gas-aggregation chamber, in which high pressure Ar gas ( 0.5-lTorr) was applied and cooled by LN2, were directly deposited onto carbon-coated films supported by Cu grids. 

FePt-based hard nanostructures have been obtained by film deposition techniques and severe cold deformation. 

This scale effect indicates that the electrical conductivity is nearly constant for the films varying in thickness from 60 to 2,000 nm. The measured resistance, however, decreased when the film thickness further reduced. Both DC and AC conductivity measurements indicated that there was an enhanced conductivity for film thickness of <60 nm. They further proposed three orders of magnitude larger conductivity in 1.6-nm-thick films than lattice conductivity. Since the grain size was not provided, it is unknown whether only the grain size plays a role when a film s thickness is less than 60 nm. Guo et al. deposited YSZ thin films by pulsed laser deposition on MgO substrates with thicknesses of 12 and 25 nm. The electrical conductivity was measured in both dry and humid O2. The electrical conductivity in thin films, however, was found to be four times lower than ionic conductivity in microcrystalline specimens, as shown in figure 10.8. Furthermore, they found that there is not any remarkable proton conduction in the nanostructured films when annealed in water vapor. 

Wet Chemical Deposition of Metal Nanoparticles and Metal Oxide Nanostructured Films on Electrode Surfaces for Bioelectroanalysis... 

On the other hand, liquid phase deposition (LPD) has been demonstrated as a flexible wet chemical method for preparing metal oxide nanostructured films on electrode surfaces. By the LPD process, electroactive titanium dioxide (Ti02) films were prepared on graphite, glassy carbon and ITO. The electrochemical properties of such LPD Ti02 films were dependent upon the film thickness controlled by the deposition time. The LPD technique was easily combined with other techniques, e.g., seed-mediated growth, which could provide metal/metal oxide composite nanomaterials. Moreover, hybrid nanostructured films were facilely obtained by doping dyes, surfactants and other... 

In this chapter, we would like to introduce two wet chemical methods, namely a seed-mediated growth approach and a liquid phase deposition process, which have been successfully utilized to modify electrode surfaces with gold nanoparticles or Ti02 nanostructured films. Because both methods are soft , the particle size or film thickness is... 

Nanostructured metal oxide film deposition can also be prepared by hydrothermal decomposition, film casting method (sonication of nanoparticles in aqueous solution (H20) or preparation of aqueous suspension of nanoparticles for spread on conducting glass plate) and nanosized metal nanoparticles prepared by controlled hydrolysis [16,18,19,21,26],... 

Raman spectroscopy was used to characterise the microstructure of ta C films deposited by filtered arc, accelerated at different energies.310 Similar data were used to examine a C films incorporating Si, Ge and N 311 and ta C films (showing an amorphous sp3 skeleton containing sp2 clusters (sizes < 1 nm.).312 Raman spectra were used to follow the nanostructuring of ta C films induced by ion-beam C implantation.313... 

Lu et al. [172] used a template assembled from uniform silica spheres to produce both an ordered macroporous Au-Ag nanostructure and an ordered hollow Au-Ag nanostructured film by electroless deposition. Both films showed SERS activity but were rather rough on the nanoscale and the authors attributed the surface enhancement to the presence of interconnected nanostructured aggregates and nanoscale roughness. 

In the following we present a Raman spectroscopy characterization of sp carbon chains embedded in a nanostructured carbon thin film deposited by SCBD. The evolution of sp carbon chains when exposed to different inert or reactive atmospheres (He, Ni, H2 and dry air), or when annealed in vacuum at various temperatures up to 200°C, has been followed by monitoring the variation of the Raman peaks associated with polyynes and polycumulenes in order to achieve detailed information about the chemical and thermodynamic stability of these species. 

Konenkamp R., Chu V., Conde J. and Dloczik L. (2001), Silicon thin film deposition on nanostructured ZnO substrates , Proc. MRS Spring Meeting, San Francisco 2001, pp. A 24-25. 

In this paper we present research on SILD technology for deposition of the mentioned above porous nanostructured SnOz layers. Last years the SILD technology excites high interest, because this method of metal oxide deposition is simple, inexpensive, and gives possibility to deposit thin nanostructured films on rough surfaces [1]. 

In this chapter we report on properties of nanometer-sized semiconductor particles in solution and in thin films and thereby concentrate on the photochemical, photophysical, and photoelectrochemical behavior of these particles. We shall, very briefly, describe the energetic levels in semiconductors and the size quantization effect. The bottleneck in small-particle research is the preparation of well-defined samples. As many preparative aspects are already reviewed in several actual assays, we present here only the preparative highlights of the last two years. In Section IV we describe the fluorescence properties of the particles. We report on different models for the description of the very complex fluorescence mechanism and we show how fluorescence can be utilized as a tool to learn about surface chemistry. Moreover, we present complex nanostructures consisting of either linked particles or multiple shells of different nanosized materials. The other large paragraph describes experiments with particles that are deposited on conductive substrates. We show how the combination of photoelectrochemistry and optical spectroscopy provides important information on the electronic levels as well as on charge transport properties in quantized particle films. We report on efficient charge separation processes in nanostructured films and discuss the results with respect to possible applications as new materials for optoelectronics and photovoltaics. 

Hybrid nanostructured films on the surface of AA2024 (A1 alloy) plates were deposited from the prepared sols by the dip coating method described in details in [3]. After coating deposition, the samples were dried at room temperature for 1 h and then heated at 120 °C for 80 min in air. 

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