Early stages of collapsing pentacene crystal by Au

Abstract

The characteristic feature of metal contacts with gold on organics is deterioration of the organic crystals during the contact formation. The unveiled key challenge is to probe dynamic details of the microscopic evolution of the organic crystal when the atomic Au is introduced. Here, we report how the collapse of the pentacene crystal is initiated even by a few Au atoms. Our results indicate that the gentle decoupling of intra and intermolecular π-π interactions causes the localization of the lowest unoccupied molecular orbital as well as the removal of cohesive forces between molecules, leading to the subsequent crystal collapse.

The Electrode's Effect on the Stability of Organic Transistors and Circuits

“…In view of the electrical, morphology, and spectral measurements, it can be deduced that some chemical or physical changes, such as disordering, and/or morphology modification, may occur pronouncedly at the Au/semiconductor interface and in its vicinity during the device operation and/or storage,31–38 which causes or accelerates the device degradation. It has been demonstrated that: i) Au can induce the modification of the molecular orbitals of pentacene, which may further lead to the breakdown of the delocalized molecular orbitals and ordered structure of the pentacene crystal film;31 ii) in actual metal/organic‐semiconductor contact systems, a substantial dipole layer may form at the interface, which will lead to a shift of the molecular energy levels and a change in the energy difference between the metal Fermi level and highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) of the semiconductor;32, 33 (iii) dewetting and molecular reorganization may occur in organic thin films on the Au surface;34–36 and iv) Au atoms can react with p‐type (pentacene) and n‐type (PTDCA) semiconductors to form covalent metal‐organic complexes 37, 38. These phenomena may provide some clues (but maybe not the real reasons yet) to understanding the influence of Au electrodes on the device stability.…”

Sub-molecular structural relaxation at a physisorbed interface with monolayer organic single-crystal semiconductors

“…5a) [33][34][35] . Conventional vacuumevaporated contacts usually cause structural disorder at the interface owing to thermal damage and/or metal penetration into the organic film, leading to fatal damage particularly in ultra-thin films [36][37][38] . It is expected that 1L crystals without any buffer layers are especially susceptible to contact deterioration.…”

Patterning of Self-Assembled Pentacene Nanolayers by Extreme Ultraviolet-Induced Three-Dimensional Polymerization

“…Previous X-ray absorption spectroscopy and X-ray diffraction studies show that a pentacene layer on silicon oxide has a good crystalline structure, as illustrated in the left side of Figure 2b. 22,24 The molecular layer of pentacene is linked together in both the lateral and vertical directions upon EUV irradiation. If the sample exposed selectively to EUV radiation is annealed up to 500 K, the physisorbed pentacene desorbs completely, but the cross-linked molecules remain on the surface, resulting in fine molecular patterns on the surface, as displayed in Figures 1c and 2a.…”

“…The EUV exposure time was increased from the bottom to the top (0−60 min). Four structures appeared at ∼0.94, 1.29, 2.14, and 2.71 eV in the expanded view of the spectrum because of intermolecular π−π interactions from the pentacene/SiO 2 layer. The two structures at ∼0.94 and 1.29 eV originate from the highest occupied molecular orbital (HOMO) and the others correspond to HOMO-1 .…”

“…In the case of direct writing, EUV radiation ( ϭ 1.9 nm) was focused into a beam with a diameter of ϳ1 m to pattern one pixel at a time. The EUV-IL exposures were performed at the XIL beamline of the Swiss light source, 22 where fully coherent EUV radiation could be utilized.…”