REVERSIBLE METAL-INSULATOR-TRANSITION IN ORDERED METAL NANOCRYSTAL MONOLAYERS OBSERVED BY IMPEDANCE SPECTROSCOPY

Low frequency impedance spectroscopy was applied on a Langmuir monolay er of alkylthiol passivated 35 Angstrom diameter silver quantum dots, as a function of interparticle separation distance. As interparticle s pacing decreases below 30% of particle diameter, a reduction in interp article charge tunneling time is observed. On further compression, the complex impedance of the films undergoes a transition from a parallel RC equivalent circuit to an inductive circuit. Optical reflectance ch anges in the films are consistent with the deduced metal-insulator tra nsition.