Electron energy loss spectroscopy of ultrathin pentacene field effect transistors

Electron energy loss spectra of ultrathin pentacene field effect transistors were measured by applying gate bias voltages. Tailing and shouldering of the primary peak on the energy loss side was observed for 1.5 nm thick films when a negative gate bias was applied. The energy loss spectra obtained from the deconvolution of the primary electron profile showed peaks, and the peak energies increased as a function of the gate bias voltage. This is consistent with the behavior of two-dimensional plasmons of field-induced carriers. The thickness dependence is explained by the thickness of the accumulation layer and the probing depth of the spectroscopy.