Investigation of the novel charge transfer complex Cd-TCNQ

Abstract

A novel metal salt of TCNQ (tetracyanoquinodimethane) has been synthesized via an electrochemical process using cadmium as donor. Thin films of the same material have been obtained by evaporating under high vacuum the metal and the organic molecule. The electronic properties of a pellet of the powdered material have been investigated by means of standard UV-VIS-IR spectroscopy, x-ray photoelectron spectroscopy, and Auger electron spectroscopy. The complex shows two absorption structures at about 3.4 eV and 1.7 eV due to the in-plane intramolecular transitions and a shoulder at about 1.4 eV probably due to the bond with the metal. The infrared spectrum is dominated by a deep absorption structure distinctive of the charge transfer. The electrical conductivity of the sample shows a semiconductor behavior in the investigated temperature range; the best fit of the transport data provides an activation energy of about 0.12 eV and shows that at low temperature the electrical conductivity is mainly due to a hopping process among differently charged sites.