Nanofabrication/nanostructure fabrication

Another benefit of creating an entire wafer of TEM windows is that arrays of windows (such as 3 x 3 matrices of windows or larger) can be used for further micro- or nanofabrication, which allows either the same nanostructure to be fabricated on all the windows in a parallel fashion or several different nanostructures to be fabricated on different windows at the same time in a serial fashion (as with EBL). The individual 5.76-mm windows can be cleaved... 

Electrochemical STM nanofabrication techniques usually involve either localized etching (dissolution), or plating (deposition) on the surface via a sharp STM tip. The first demonstration of nanostructuring was reported by Penner s group. They fabricated silver and copper nanoclusters of 20-50 nm wide and 1-7 nm high at predetennined position in the deposition process. In addition to metal clusters the deposition method was used to fabricate nano-sized polyaniline. The authors used a pulse voltage technique and fabricated polyaniline spots 10-60 run in diameter and 1-20 run in height. 

Compared to block copolymers, there have been relatively fewer examples of using homopolymers for nanofabrication. Nevertheless, some polymers with amphiphilic properties were also used in the fabrication of nanostructures with various metal salts/complexes. For example, polyaniline (PANI) emeraldine base formed self-organized mesomorphic structures when mixed with Zn(DBS)2 by the coordination between Zn2+ and the imine nitrogen atoms on the polymer main chain.100 The resulting supramolecule PANI[Zn(DBS)2]0.5 had a comb-shaped... 

There are several references reporting on template-assisted approaches for nanofabrication such as Hulteen and Martin. They are regarded as one of the pioneer groups for functional nanowire array fabrication. With the use of a periodic structured template, one-dimensional nanostructures can be prepared thanks to the confinement effect of the porous template. The templates can be prepared easily with anodization. Control of the aspect ratio and the area density of one-dimensional nanostructures can be achieved by changing the diameter and length of the template, and by changing the anodization voltage. 

Microphase separation (MPS) leading to regular patterns at nanometer levels formed by block copolymers in thin films has recently been a subject of intensive study. Such nanostructures allow for fabrication of even smaller feature sizes than those obtained by the conventional photolithography process, and have potentials for future nanofabrications (Lazzari et al., 2006). Attempts to create active and photocontrollable MPS systems are a fascinating challenge. 

The basic difference between conventional processing and nanofabrication is the dimension of the structures to be fabricated. There are basically two possible approaches top-down and bottom-up approaches. In the top-down approach, micro and nanostructures are achieved by controlled removal of extra amount of material by applying an external source of energy such as mechanical, thermal, chemical, and electrochemical energy. The top-down approach of micro and nanofabrication is schematically shown in Fig. 1.2. This approach is difficult to apply at nanoscale however at microscale, it has been utilized successfully by various means. In the bottom-up approach, positions of atoms or molecules are manipulated to build up the nanodevices or nanostmctures, as illustrated in Fig. 1.3. Various techniques of this approach are under development at the laboratory level and need further improvements. 

Chapter 12 focuses on recent advancements in EMM for micro and nanofabrication. It contains various emerging variants of EMM. Various interesting factors of surface structuring of aluminum, stainless steel, and titanium, etc., by EMM have been presented considering not only simple flat surfaces but also complex curved surfaces. EMM can also be successfully utilized for fabrication of three-dimensional nanostructures which has also been reported. 

D machining of electrochemically active materials, including the construction of unconventional island patterns on a surface with nanoscale resolution, was also realized by this method [95, 115-117]. Thus, electrochemical machining can be applied to microelectromechanical systems (MEMS] [118] and even in the nanoelectromechanical systems (NEMS]. Electrochemical methods can realize the nanofabrication in a selective place and make the complicated 3D nanostructures. Conducting polymers can also be fabricated in this way. Similar to the electrochemical machining, by application of short voltage pulses to the tool electrode in the vicinity of the workpiece electrode, the electropolymerization... 

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