Electronic structure of undoped and potassium-doped coronene investigated by electron energy-loss spectroscopy

Abstract

We performed electron energy-loss spectroscopy studies in transmission in order to obtain insight into the electronic properties of potassium intercalated coronene, a recently discovered superconductor with a rather high transition temperature of about 15 K. A comparison of the loss function of undoped and potassium intercalated coronene shows the appearance of several new peaks in the optical gap upon potassium addition. Furthermore, our core level excitation data clearly signal filling of the conduction bands with electrons.

Electronic excitation spectrum of doped organic thin films investigated using electron energy-loss spectroscopy

“…In a first step, we have always characterized the structure of the films using in-situ electron diffraction. This demonstrated a polycrystalline structure of the films [23,41], which in the case of K doped picene agrees well with data from x-ray diffraction [18]. In other words, the films consist of crystalline grains that are larger than the wave-length of the studied plasmons.…”

Properties of crystalline coronene: Dispersion forces leading to a larger van der Waals radius for carbon

“…The Kohn–Sham bandgap E gap = 2.51 eV. The experimental values, known to us, equals 2.91 eV from fluorescence emission experimental data 53 and an optical gap of 2.8 eV 54. The calculated E gap value is understated.…”

Loss spectroscopy of molecular solids: combining experiment and theory

“…For the present work, large thin films of organic compounds have also been produced by thermal evaporation under high vacuum onto single crystalline substrates (e.g. KBr) kept at room temperature (for details of this procedure and an overview over the parameters used see [23][24][25]). These thin films were floated off in distilled water, mounted onto standard electron microscopy grids and transferred into the spectrometer.…”