Published online by Cambridge University Press: 21 February 2011
Microwave investigations on sub-pm (“mesoscopic”) metal crystals revealed a size-induced metal-insulator transition (SIMIT). The microwaves were applied to determine the sizedependent quasi-static conductivity of metal crystals dispersed in an insulating matrix. Choosing an indium colloid for a model system allowed an in-situ particle size variation from 10 nm up to about 1μm. The experiments were carried out in a microwave bridge at 10 GHz, a frequency where the oscillation time is much longer than the elastic scattering time of electrons in a metal (quasi-static limit). The conductivity of metal crystals was found to decrease approximately with their volumes in the above size range. The 3-dimensional confinement of the electron wave packets gives rise to quantum-mechanical interference effects leading to the SIMIT as the crystals become smaller than 1μm. Experimental details and results including the sizeaffected temperature dependence of the conductivity are presented. The universal significance of the SIMIT and its consequences for the engineering of novel materials and the ultimate size-reduction in microelectronic devices are discussed as well.,