Quantum wire structures, formed

Fig. 6.26. A strained quantum wire structure formed in the patterned surface of a substrate.

In a manner analogous to confining the movement of an electron to a two-dimensional plane as in a quantum well structure, additional confinement conditions can also be imposed to realize confinement in both one and zero dimensions, to generate quantum wire and quantum dot structures (see Fig. 7). These structures can be realized physically by having a semiconductor material take on the form of an ultrasmall rectangular-shaped wire or an ultrasmall box, where the surrounding material is another semiconductor material of wider bandgap. For the quantum wire structure, the wire acts as a potential well that... 

Superlattice and low-dimensional physics are some of the most interesting subjects in solid-state physics. A challenging problem in this field is the formation of quantum wire and quantum box structures by using ultra-high technology such as MBE, MOCVD (metallorganic chemical vapor deposition), and related frontier microprocessing. However, this problem has not yet been solved. Poly silane is probably a perfect quantum wire in itself The absorption spectrum of polysilane clearly shows the characteristics of a one-dimensional quantum wire. Even a quantum box or a one-dimensional superlattice can be formed by chemical polymerization, which may be the simplest way. 

In relation to the primary topic of this section, nanotubes are interesting structures to contemplate. In the semiconducting state, the gaps can range from 0.7 to 1.4 eV and hence could provide sufficient overlap with the solar spectrum for good collection efficiency. In the metallic state they could also serve as 1-D quantum wires forming a barrierless conduction path between donor and acceptor states and facilitate charge... 

Fig. 6.28. Part (a) shows a schematic illustration of a quantum wire in a V-groove formed by patterning a 100 surface of a cubic crystal substrate, with the glide dislocation on a 111 crystallographic plane within the structure. The conditions for formation of such a dislocation are considered in terms of a superposition of the stress fields of the configurations depicted in parts (b) and (c). The superposition scheme is described in the text.

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