Surface-Enhanced Raman Spectroscopic Studies of Metal-Semiconductor Interfaces in Organic Field-Effect Transistors

The performance of organic field-effect transistors (OFETs) largely depends on the nature of interfaces of dissimilar materials. Metal-semiconductor interfaces, in particular, play a critical role in the charge injection process. This work demonstrates the unique potential of Raman and surface-enhanced Raman scattering (SERS) for the investigation of physical phenomena at the nanoscale in pentacene-metal interfaces in OFETs. A large enhancement in the Raman intensity (SERS) is observed from pentacene films under thermally evaporated Au films. Comparing experiments with density functional theoretical calculations of the Raman spectrum of pentacene indicates the presence of disordered sp(2) carbons. Changes in the Raman spectra are further tracked after biasing the devices. Raman maps across the pentacene Au interface provide a powerful visualization tool for correlating the device performance with structural changes of the molecule.