Correlating growth mechanism and morphology in Cu-TCNQ organometallic complex: A microscopic study

The structure-property correlation in the Cu-TCNQ organometallic complex is very important for explaining its unusual electrical, optical and magnetic properties. Consequently several morphological studies and their correlation with the properties of these materials can be found in the literature, although no systematic study of various morphologies with growth conditions and their correlation has been reported to the best of our knowledge. Therefore in this manuscript the interconversion of various morphologies is reported using electron and probe microscopies. A conventional Cu TEM grid acted as the copper source to form a Cu-TCNQ complex and the complex, which formed at the surface of the TEM grid. The complex thus prepared was characterized by FTIR and Raman spectroscopic techniques. The shifting of ̵-CN from 2221 cm^-1 (TCNQ) to 2201 cm^-1 indicates formation of a complex and the identical nature of IR spectra in two phases indicates that they are polymorphs. The morphologies of Cu-TCNQ were followed through FE-SEM and TEM studies. Various morphologies such as needle, square tube, platelet etc. were observed as a function of time. A distinct transition from needle to platelet morphology was observed as the complex grew. The conductance of various morphologies in phase-I as well as phase-II were also measured and compared by Spreading Resistance Imaging (SRI) at different bias voltage i.e. 1 V, 3 V and 5 V.