Surface confined heterostructures

Fig. 3. The lattice-matched double heterostructure, where the waves shown in the conduction band and the valence band are wave functions, T(x), representing probability density distributions of carriers confined by the barriers. The chemical bonds, shown as short horizontal stripes at the AlAs—GaAs interfaces, match up almost perfecdy. The wave functions, sandwiched in by the 2.2 eV potential barrier of AlAs, never see the defective bonds of an external surface. When the GaAs layer is made so narrow that a single wave barely fits into the allotted space, the potential well is called a quantum well. Because of the match in the atomic spacings between GaAs and AlAs, 99.999% of the interfacial chemical bonds are saturated.

Nano-confinement of metal and semi-conductor materials can lead to marked changes in their electronic behaviour. Their unique properties resulted in an increased interest in using these nanoparticles (NPs) in materials science. Furthermore, with the discovery of the symbiotic nature of metal/semi-conductor heterostructures, the use of NPs in applications such as photocatalysis and opto-electric devices, like photovoltaic cells, has increased. The exceptional properties of carbon nanotubes (CNTs), as well as their unique structure, have led to increased investigation into their behavior in such hetero-structured complexes. Large surface-to-volume ratios, chemical inertness, and lack of porosity make CNTs prime candidates as catalyst supports. In more complex systems, the electrical properties of the CNTs increase the yield of catalyzed reactions due to the electronic interactions of certain NPs and CNTs. Based on the fact that charge transfer between quantum dots and CNTs has been reported, certain semi-conducting NPs have been covalently linked to CNTs to make hetero-junction electronic devices. ... 

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