Nanostructures deposition techniques

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. 

All the metallic nanostructures deposited by laser electrodispersion on both types of silicon substrates were found to be exceedingly active in the above processes. The activity was orders of magnitude higher than that of typical supported catalysts prepared by the standard techniques. Such a high activity is presumably due not only to the small size and amorphous state of nanoparticles, but also to the influence exerted by the charge effects discussed above. 

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

The technique of layer deposition and coating has a variety of industrial applications, such as protective layers, sensors, resistive films and catalyzers. We will briefly present the different deposition techniques as a function of the nanostructures obtained for ... 

Thin film devices can be fabricated by an electrophoretic deposition technique. In the electrophoretic deposition method, the materials are applied as colloidal particles in a non-solvent. By subjecting the particles to an electrophoretic force, a nanostructured film is formed. Drying of the film is done under non-solvent conditions in order to keep the structure. 

Next, the template-assisted nanostructured deposition of NiO was tried, following the experimental method of Sonavane et al. for the electrodeposition of nontemplated coatings [62]. For this purpose a 0.5M aqueous NiCl bath containing 0.1 M KCl was prepared, which was complexed using EDTA and pH-adjusted to 8 by addition of KOH. Electrodeposition was conducted in a three-electrode cell at a potential of -1.1 V versus Ag/AgCl for lOOmin. The obtained DG-structure NiO film of about 1 ttm thickness is presented in Fig. 5.5. This preparation technique has two major disadvantages firstly, the very slow deposition rate, and secondly, the transparency of the deposit complicates the anyway difficult preparation route. In Chap. 6, a more elegant approach for nanostructured NiO deposition is presented that overcomes these issues. 

The planar order of nanostructures deposited by chemical routes has become an important issue, because of the competition with solid-state nanotechnology cap>able of the fabrication of fine two-dimensional structures. The main concern is with the layers of nanopartides produced by chemical self-assembly, because methods of electrostatic self-assembly and LB is not capable of producing two-dimensional ordered arrays of nanopartides. The features of the lateral arrangement of particles, which are buried under layers of either closely packed amphiphilic compounds or polymers, are usually smeared and difficult to observe. In the case of relatively thick (quasi-3D) films, produced by electrodeposition and sol-gel techniques, the morphology study usually reveals polycrystallites. Therefore, the quality of these materials can be assessed by the size of the crystallites and by the presence of preferential orientation, which may cause anisotropy of the electrical and optical prop>erties of materials. 

The principle and the research progress in the electrophoretic sol-gel deposition technique, which is combined sol-gel method for particle preparation and electrophoretic deposition of the sol-gel derived particles, have been described. In the principal, (1) preparation of particles by the sol-gel method, (2) deposition of particles by electrophoresis, (3) constant-voltage and constant-current deposition, and (4) solvent and electrification are introduced, hi the practical application, (1) silica thickfihns, (2) titania thick films, (3) polysilsesquioxane thick films, and (4) template-based oxide nanorods are illustrated. The electrophoretic sol-gel deposition technique offers the advantages of functional coatings in various research fields such as chemically and mechanically protective, electrically conductive, photocatalytic and bioactive materials, and it expands the possibility of fabricating optical components and ahgned micro- and nanostructures. 

NSL—often called colloidal lithography (CL)— is an effective technique using self-assemblies of polystyrene (PS) micro- or nano-particles on solid surfaces as 2-or 3-dimensional masks for metal deposition (Zhang et al. 2010). The size and shapes of the close-packed nanospheres and the holes between them, in addition to the metal deposition conditions, such as evaporation angle or specific deposition technique (e.g., sputtering, thermal deposition), influence the achieved metallic patterns. A different kinds of metallic nanostructures can he obtained (Fig. 3.10) ... 

Over recent years, substantial progress has been made in the development of methods to synthesise new anatase nanostructures such as nanoparticles, nanorods, nanowires, nanobowls, nanosheets and nanotubes, and mesoporous materials such as aerogels, opals, and photonic materials.These methods include sol and sol-gel, micelle and inverse micelle, hydrothermal, solvothermal, sonochemical, microwave deposition techniques, direct oxidation, chemical vapour deposition, physical vapour deposition, and electrodeposition. For DSSC, the most common deposition technique is the sol-gel method from hydrolysis... 

The length scale plays a vital role in heterogeneous catalysis to control the structure, active phase and overall framework of the catalyst system. In the CMR, catalysis by nano-scale materials will improve the physico-chemical properties of the catalytic membrane. A uniform nanostructured catalytic membrane was prepared using AAO and atomic layer deposition techniques and tested in oxidative dehydrogenation of cyclohexane. Nanostructured CMs have excellent properties, such as uniform pores, contact time control, uniform diffusion paths and active site isolation (no sintering), compared... 

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