Electronic, morphological and transport properties of 6,13-pentacenequinone thin films: Theory and experiments

We investigated the electronic, morphological and transport properties of 6,13-pentacenequinone thin films grown by vacuum thermal evaporation gram on silicon oxide (native and thermally grown) substrates at room temperature using X-ray photoemission spectroscopy, atomic force microscopy and in situ transport measurements. The chemical properties of the molecule have been characterized by high resolution C1s, O1s and Valence Band X-ray photoemission as a function of the thickness and the photoemission peaks were interpreted on the basis of density functional theory calculations. The photoemission analysis of the above mentioned regions reveals characteristic features (namely a double peak on C1s due to the six inequivalent carbon atoms, a single peak on O1s at binding energy of 531.3 eV and a feature centered at 3.7 eV assigned to a convolution of the highest occupied molecular orbitals). Atomic force microscopy measurements show an initial amorphous wetting layer with a subsequent island growth in two different crystalline phases, namely the bulk crystal phase and a metastable substrate induced phase. Finally, electrical measurements evidence the insulating character of 6,13-pentacenequinone films with a resistivity ρ ⩾ 5 × 106 Ω m.