Top-down nanofabrication

In addition, traditional top-down nanofabrication methods such as focused ion beam (FIB], can be used to fabricate nanopore array electrodes [225], FIB milling thus represents a simple and convenient method for fabrication of prototype nanopore electrode arrays. These electrode nano-arrays can be used in electrochemical nanofabrication for applications in sensing and fundamental electrochemical studies. 

Top-Down Nanofabrication Manufacturing technique that removes portions of larger materials to create nano-sized materials. 

Top-Down Nanofabrication. Top-down nanofabrication is a process in which a larger amount of material is used at the start. The desired nanomaterial is created by removing, or carving away, the material that is not needed. This is less time-consuming than... 

The top-down nanofabrication has been used with obvious success by the semiconductor industry for several decades now, with physicists and engineers manipulating progressively smaller pieces of matter by photolithography and related techniques, but the top-down approach is quickly reaching its physical and economic limits. On the other hand, the bottom-up nanofabrication offers ultimate limits of miniaturization, opens virtually unlimited possibilities concerning the design and construction of functional nanostructured materials, and has the potential to be... 

We can peer into the future with reasonable confidence. We can be confident that we will witness many breakthroughs based on bottom-up approaches in the next decades, leading to nanostructured materials with novel and unique material properties and functionalities, and to increasingly sophisticated nanodevices. While cnrrent indications are that bottom-up nanofabrication methods will not completely replace top-down nanofabrication techniques, in the decades to come we will see more applications originating either from bottom-up techniques alone or from hybrid approaches combining the strengths of bottom-up and top-down methods. 

Table 2. Some Approaches in Reductive (Top Down) and Synthetic (Bottom Up) Nanofabrication...

In order to achieve improved nanofabrication performance, novel functional block copolymer systems are strongly desired. Many researchers have recognized this, and novel functional systems such as metal-containing block copolymer systems have significantly simplified and improved nanofabrication processes. The combination of top-down microscale patterns with the bottom-up nanopatterns are attractive for integrating functional nanostructures into multipurpose on-chip devices. However, in order to use these materials in real-time applications, further development is still needed. More ground-shaking discoveries are needed and are also fully expected. 

TABLE 2 SOME APPROACHES IN REDUCTIVE (TOP DOWN) AND SYNTHETIC (BOTTOM UPi NANOFABRICATION... 

These experiments demonstrate a peculiar crossover of two conceptually different approaches in nanofabrication, i.e. the top-down approach using lithographic techniques and the bottom-up approach using self-assembly of elementary building blocks. From one side, constructing things one-atom-at-a-time... 

Dimensions between the atomic/molecular and the bulk macroscopic scales are sometimes called mesoscopic. Because the mesoscopic scale corresponds roughly to the electron free path, unusual phenomena such as quantum effects can be observed, some of which could be used in the development of single-electron devices or quantum computers. Top-down-type nanofabrication techniques are now capable of producing structures in this size range, and research on this subject has received significant attention, especially in the held of semiconductor science and technology. 

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. 

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