Fabrication of Nanostructures in the Templates

In this case one can get templates with sizes of the order of a micron. 

Making templates of ordered nanopores is the starting point for template based nanolithography. The next step involves filling the pores of the membrane with different materials of interest using one or more available methods. The methods include electrochemical deposition (ED), vapor phase deposition such as chemical vapor deposition (CVD), pressure injection of molten metals and sol-gel methods. In this section we describe some of the methods of deposition in the nanopores. 

Spin coat and heat above Tg of both polymers 

The chemical routes that are follotved depend on the material to be deposited. In the case of metals or oxides that can be made easily by oxidizing the metal, the most popular route is electrochemical deposition. For more complex materials like functional oxides a sol-gel method is often used. For materials like GaN or carbon nanotubes the preferred method is CVD. In the subsequent subsections ve give some details of the methods with examples. 

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Sasaki, M., Osada, M., Sugimoto, N., Inagaki, S., Fukushima, Y., Fukuoka, A. and Ichikawa, M. (1998) Novel templating fabrication of nanostructured Pt clusters and wires in the ordered cylindrical mesopores of FSM-16 and their unique properties in catalysis and magnetism. Microporous and Mesoporous Materials, 21, 597. 

In addition to chemical or physical properties, a fascinating aspect of fullerene related materials is their central empty space, where atoms, molecules or particles can be enclosed. The enclosed particles are then protected by the robust graphitic layers from chemical or mechanical effects. The very long cavities of CNTs have a special potential due to their high aspect ratio and they can be used as templates to fabricate elongated nanostructures. 

The formation of nanostructures such as nanodot arrays has drawn a great attention due to the feasible applications in a variety of functional structures and nanodevices containing optoelectronic device, information storage, and sensing media [1-3]. The various methods such as self-assembled nanodots from solution onto substrate, strain-induced growth, and template-based methods have been proposed for the fabrication of nanodot arrays on a large area, [4-6]. However, most of these works can be applied to the small scale systems due to the limited material systems. 

Nucleic acids, DNA and RNA, are attractive biopolymers that can be used for biomedical applications [175,176], nanostructure fabrication [177,178], computing [179,180], and materials for electron-conduction [181,182]. Immobilization of DNA and RNA in well-defined nanostructures would be one of the most unique subjects in current nanotechnology. Unfortunately, a silica surface cannot usually adsorb duplex DNA in aqueous solution due to the electrostatic repulsion between the silica surface and polyanionic DNA. However, Fujiwara et al. recently found that duplex DNA in protonated phosphoric acid form can adsorb on mesoporous silicates, even in low-salt aqueous solution [183]. The DNA adsorption behavior depended much on the pore size of the mesoporous silica. Plausible models of DNA accommodation in mesopore silica channels are depicted in Figure 4.20. Inclusion of duplex DNA in mesoporous silicates with larger pores, around 3.8 nm diameter, would be accompanied by the formation of four water monolayers on the silica surface of the mesoporous inner channel (Figure 4.20A), where sufficient quantities of Si—OH groups remained after solvent extraction of the template (not by calcination). 

The use of block copolymers to form a variety of different nanosized periodic patterns continues to be an active area of research. Whether in bulk, thin film, or solution micelle states, block copolymers present seemingly unlimited opportunities for fabricating and patterning nanostructures. The wealth of microstructures and the tunability of structural dimensions make them a favorable choice for scientists in a variety of research fields. As reviewed here, they can function as nano devices themselves, or act as templates or scaffolds for the fabrication of functional nanopatterns composed of almost all types of materials. However, there are still two obvious areas which require more work control of the long-range 3D nanostructure via more user-friendly processes and the identification of new materials with different functional properties. 

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