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 sampl es exhibit metallic behavior. However, the effective Debye temperature characterizing the resistivity variation is found to decrease drastic ally as the particle size is reduced from 6.0 to 4.0 nm. This arises d ue to a larger fraction of atoms residing at the surface of the partic les. Nanoparticles of silver, copper, and iron, respectively, with dia meters 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 re sistivity indicates a temperature dependent activation energy. The dat a cannot, however, be fitted to either a T--1/2 or T-(1/4) law. The ac tivation energy in the temperature range 200 to 300 K is controlled by an electron tunneling mechanism between the metal grains. In the lowe r temperature range a quantum size effect appears to be operative givi ng rise to a very low activation energy of the order of a few meV.