Molecular machine semiconductor

The selected examples in this chapter demonstrate the success of the development of photoswitchable molecular materials through the rational designs based on the coupling of photochromic moieties into molecules with different functions, such as luminescence, nonlinear optics, liquid crystal, molecular machine, receptor, electrical con-ductor/semiconductor, and many others. It is important to emphasize that photoswitchable materials are not confined only to the selected areas in these examples. With the understanding of both the photoswitching processes and the functional properties at the molecular levels, materials that possess different varieties of photoswitchable functional properties can be readily designed and synthesized. 

Merkle (5) conveniently divided molecular- and nano-scale simulations into two categories - those which rely on force-field based molecular-mechanics methods (no explicit electronic information) which are utilized for modeling nano-machines, and those that are quantum based, which are suitable for nano-electronic components and devices. Force field methods have been enq)loyed to simulate numerous nano-mechanical phenomena and conq)onents including Drexler-Merkle gears and neon pumps (6), carbon nanotube based gears (7), atomic-scale friction (8) and semiconductor nanostructures (9). 

Electrodeposition of semiconductors is a low-cost process. The most expensive equipment used in the process is a computerized potentiostat which may cost up to 5,000 compared to techniques like molecular beam epitaxy (MBE) or metal organic vapor phase epitaxy (MOVPE) in which the cost of the machines is in the order of 1 million. In addition, electrodeposition is versatile in application in the sense that many semiconductor materials can be electrodeposited using the same equipment. The only change required is basically the replacement of the deposition electrolyte by the desired one at any time. Evidence of a variety of electrodeposited semiconductors includes CdTe [32-42], CdS [10,32], ZnSe [11], ZnTe [12-14], SnS [17], CuInSea [18-22], CuInGaSe2 [23-27], and nitrides [9,43]. 

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