Combined electrical and Raman characterization of C60-based organic field effect transistors

摘要

Raman spectroscopy is capable of distinguishing neutral and charged states of organic molecules due to its sensitivity for charge induced changes in the molecular geometry and the bond strength.Combined with in situ electrical measurements it provides a powerful tool for characterizing charged molecules in the channel of organic field effect transistors OFETs. The active 3nm C60 layer in an OFET structure with bottom gate con figuration was characterized by in situ Raman spectroscopy using the 514.5 nm (2.41 eV)Ar~+ laser line as a function of the drain source (V_(ds)) voltage. The Raman spectra show pronounced changes upon application of a drain source Vds voltage. The experimental findings are compared to the vibrational spectra calculated for molecules under external bias fields. Complementary to the Raman characterization,the I_d-V_(ds) and I_d-V_(gs) characteristics were recorded and the mobility value of 0.1 cm~2/V s was derived from these measurements.