Effects of graphene defect on electronic structures of its interface with organic semiconductor

Abstract

Electronic structures of copper hexadecafluorophthalocyanine (F16CuPc)/graphene with different defect density were studied with ultra-violet photoelectron spectroscopy. We showed that the charge transfer interaction and charge flow direction can be interestingly tuned by controlling the defect density of graphene through time-controlled H2 plasma treatment. By increasing the treatment time of H2 plasma from 30 s to 5 min, both the interface surface dipole and the electron transporting barrier at F16CuPc/graphene interface are significantly reduced from 0.86 to 0.56 eV and 0.71 to 0.29 eV, respectively. These results suggested that graphene's defect control is a simple approach for tuning electronic properties of organic/graphene interfaces.

Impact of Graphene Work Function on the Electronic Structures at the Interface between Graphene and Organic Molecules

“…The UPS spectra for graphene on NH 2 -SAM, SiO 2 , and F-SAM are shown in Figure 2. Without surface modification using SAMs, the WF of graphene is ~4.40 eV, showing good consistency with previous reports [45]. In the case of graphene on the NH 2 -SAM, the WF decreases to ~3.90 eV, which is evidenced by the shift of secondary electron cutoff toward the lower kinetic energy part.…”

Plasma engineering of graphene

“…They determined that hydrogenation opened up a band gap transforming graphene from highly conductive semimetal to insulator. 118 This indicates that tuning the defect density in graphene by hydrogen plasma is a suitable for controlling electronic transport characteristics and performance of organic electronic devices with graphene electrodes. Figure 16 shows the band alignment between graphene and F 16 CuPc with plasma treatment.…”

Transition-Metal Phthalocyanines on Transition-Metal Oxides: Iron and Cobalt Phthalocyanine on Epitaxial MnO and TiOx Films

“…2,10,11 Comparable interactions occur at the interface between FePc and metals such as silver, 12−14 gold, 15 or nickel. 16 Such interactions can be tuned by the introduction of graphene as an intermediate layer, e.g., between the TMPc and a nickel or iridium substrate 3,17,18 For gold and silver substrates, a change of the molecular spin of TMPc after adsorption on the substrate was reported. 4,6,9 Furthermore, recent studies investigating magnetic couplings revealed a strong intermolecular antiferromagnetic coupling of CoPc in the form of powder and thin films 19 and, in the case of MnPc, a ferromagnetic coupling between cobalt substrate and the first layer of the organic material.…”

“…For instance, for CoPc at the interface to metals such as gold, − silver, ,− or nickel, a local charge transfer into empty Co states was observed, which can be accompanied by a back-donation via the ligands resulting in a positive charge accumulation at the ligands. ,, Comparable interactions occur at the interface between FePc and metals such as silver, − gold, or nickel . Such interactions can be tuned by the introduction of graphene as an intermediate layer, e.g., between the TMPc and a nickel or iridium substrate ,, For gold and silver substrates, a change of the molecular spin of TMPc after adsorption on the substrate was reported. ,, Furthermore, recent studies investigating magnetic couplings revealed a strong intermolecular antiferromagnetic coupling of CoPc in the form of powder and thin films and, in the case of MnPc, a ferromagnetic coupling between cobalt substrate and the first layer of the organic material . In view of applications such as spintronic devices or solar cells, transition-metal oxides (TMO) might be promising substrates.…”