6.1. SOLID DISORDERED NANOSTRUCTURES
145
Figure 6.15. Sketch of a model to explain the electrical conductivity in an ideal hexagonal array
of single-crystal gold clusters with uniform intercluster resistive linkage provided by resistors
connecting the molecules. (With permission from R. P. Andres et al., in Handbook of Nanostructured Materials and Nanotechnology, H. S. Nalwa, ed., Academic Press, San Diego, 2000,
Vol. 3, Chapter 4, p. 221 .)
conduction is electron tunneling from one metal cluster to the next. Section 9.5 (of
Chapter 9) discusses a similar case for smaller gold nanoparticles.
The tunneling process is a quantum-mechanical phenomenon where an electron
can pass through an energy barrier larger than the kinetic energy of the electron.
Thus, if a sandwich is constructed consisting of two similar metals separated by a
thin insulating material, as shown in Fig. 6.16a, under certain conditions an electron
can pass from one metal to the other. For the electron to tunnel from one side of the
junction to the other, there must be available unoccupied electronic states on the
other side. For two identical metals at T= 0 K, the Fermi energies will be at the same
level, and there will be no states available, as shown in Fig. 6.16b, and tunneling
cannot occur. The application of a voltage across the junction increases the
electronic energy of one metal with respect to the other by shifting one Fermi
level relative to the other. The number of electrons that can then move across the
145
Figure 6.15. Sketch of a model to explain the electrical conductivity in an ideal hexagonal array
of single-crystal gold clusters with uniform intercluster resistive linkage provided by resistors
connecting the molecules. (With permission from R. P. Andres et al., in Handbook of Nanostructured Materials and Nanotechnology, H. S. Nalwa, ed., Academic Press, San Diego, 2000,
Vol. 3, Chapter 4, p. 221 .)
conduction is electron tunneling from one metal cluster to the next. Section 9.5 (of
Chapter 9) discusses a similar case for smaller gold nanoparticles.
The tunneling process is a quantum-mechanical phenomenon where an electron
can pass through an energy barrier larger than the kinetic energy of the electron.
Thus, if a sandwich is constructed consisting of two similar metals separated by a
thin insulating material, as shown in Fig. 6.16a, under certain conditions an electron
can pass from one metal to the other. For the electron to tunnel from one side of the
junction to the other, there must be available unoccupied electronic states on the
other side. For two identical metals at T= 0 K, the Fermi energies will be at the same
level, and there will be no states available, as shown in Fig. 6.16b, and tunneling
cannot occur. The application of a voltage across the junction increases the
electronic energy of one metal with respect to the other by shifting one Fermi
level relative to the other. The number of electrons that can then move across the