Electronic transport through electron-doped Metal-Phthalocyanine Materials

TL;DR

This study investigates the insulator-metal-insulator transition in alkali-doped metal phthalocyanine films, revealing new crystalline phases and charge transfer phenomena similar to those in C60, with implications for molecular magnetism and electronic phases.

Contribution

It demonstrates a reversible insulator-metal-insulator transition in MPc films due to alkali doping, highlighting new crystalline phases and charge transfer mechanisms.

Findings

Doping induces a metallic state in MPc films.

Further doping reverts films to insulating state.

Structural studies confirm new crystalline phases.

Abstract

We report an insulator-metal-insulator transition in films of five metal phthalocyanines (MPc) doped with alkali atoms. Electrical conduction measurements demonstrate that increasing the alkali concentration results in the formation of a metallic state for all systems. Upon further doping, the films reenter the insulating state. Structural and Raman spectroscopy studies reveal the formation of new crystalline phases upon doping and are consistent with the phenomena originating from charge transfer between the intercalated alkali atoms and MPc, in a similar fashion to what has been so far observed only in C60. Due to the presence of a molecular spin, large exchange energy, and a two-fold orbital degeneracy in MPc, our findings are of interest in the study of controllable magnetism in molecular materials and in the investigation of new, recently predicted electronic phases.