Photoemission and Transport Studies of the Metal-Insulator Transition in Granular Palladium Films

Abstract

Photoemission and resistivity measurements of granular Pd samples are reported which exhibit a metal-insulator transition with decreasing metal fraction. As the net metallic concentration is reduced the resistivity passes through $\sqrt{T}$, $\ln T$, $\exp \{+{\left(\frac{A}{T}\right)}^{\frac{1}{4}}\}$, and insulating $\exp \{+{\left(\frac{B}{T}\right)}^{\frac{1}{2}}\}$ temperature dependences while the photoemission results show a continuous reduction in the Pd local density of states within 1 eV of the Fermi level. In the insulating regime a gap is observed in the photoemission spectrum.