Electrical properties of glass-metal nanocomposites synthesized by electrodeposition and ion exchange/reduction techniques

Glass-metal nanocomposites involving silver have been grown within ion-exchanged lithia silicate glasses by an electrodeposition technique. The silver particle diameters range from 4.0 to 12.0 nm, depending on the alkali ion concentration in the precursor glass. Most of the samples exhibit metallic behavior. However, the effective Debye temperature characterizing the resistivity variation is found to decrease drastically as the particle size is reduced from 6.0 to 4.0 nm. This arises due to a larger fraction of atoms residing at the surface of the particles. Nanoparticles of silver, copper, and iron, respectively, with diameters ranging from 6.6 to 11.6 nm have also been grown within a glass-ceramic by an ion exchange and reduction technique. The electrical resistivity indicates a temperature dependent activation energy. The data cannot, however, be fitted to either a T~mor T~mlaw. The activation energy in the temperature range 200 to 300 K is controlled by an electron tunneling mechanism between the metal grains. In the lower temperature range a quantum size effect appears to be operative giving rise to a very low activation energy of the order of a few meV.