Molecular interactions on epitaxial graphene

Face-on stacking and enhanced out-of-plane hole mobility in graphene-templated copper phthalocyanine

“…Face-on packing occurs when molecule-substrate interactions dominate over molecule-molecule interactions, and is common for planar aromatic molecules deposited on graphite due to p interactions between the molecules and graphite. 1,10,11 Ordered monolayers of planar molecules on graphite, deposited from vacuum 1,12 and solution, 13 have been resolved by scanning tunnelling microscopy, and in some cases, face-on stacking has been shown to persist in multilayer films. 1,14 Graphene, having a comparable surface chemistry to graphite, exhibits a similar templating effect on organic semiconductor overlayers.…”

“…1,14 Graphene, having a comparable surface chemistry to graphite, exhibits a similar templating effect on organic semiconductor overlayers. 11,[15][16][17] A distinct advantage of graphene over graphite, however, is that the former can readily be transferred to arbitrary substrates for surface functionalization and integration into organic electronic devices. 18 Surface functionalization is a versatile means of manipulating molecular organization and electrical function in organic semiconductor thin films.…”

Self-Assembled Two-Dimensional Heteromolecular Nanoporous Molecular Arrays on Epitaxial Graphene

“…For example, noncovalent chemical interactions available between many organic molecules promote the formation of self-assembled adlayers with highly ordered 2D structures. − The resulting structure of the organic adlayers depends on three primary factors, (1) the size parameters and symmetry that characterize the molecules and the substrate; (2) the degree of mismatch between the lattice constants that define the organic film and the surface reconstruction; and (3) the relative strengths of the adsorbate–adsorbate and adsorbate–substrate interactions. Under favorable conditions, it is possible to rationally select organic molecules with the appropriate intermolecular and molecule–substrate interactions to form highly ordered 2D crystals on graphene …”

F4-TCNQ on Epitaxial Bi-Layer Graphene: Concentration- and Orientation-Dependent Charge Transfer at the Interface

“…Understanding and regulating molecular orientation have a significant impact on the molecules’ physical characteristics, such as their charge transport properties, and their corresponding performance in optoelectronic devices. − In device application, for example, in organic light-emitting diodes, , the tetrafluoro-tetra cyano quinodimethane (F4TCNQ) molecule, a strong molecular electron acceptor, has been utilized effectively as the p-type dopant in the relevant materials. − In the application of carbon-based nano-electronics, owing to its unique properties, graphene is known as an excellent candidate, where particularly epitaxial graphene grown on silicon carbide (EG/SiC) presents viable opportunities for large-scale graphene samples, which is important for the practical applications. , However, epitaxial graphene (EG) on SiC(0001) is affected by strong intrinsic n-type doping because of the graphene/SiC interface properties, which causes the Fermi energy, E F , to be shifted away from the Dirac point energy, E D , where the pi bands cross, preventing the novel ambipolar properties of graphene from being utilized. It has been already demonstrated that a complete compensation for the excess negative charge can be achieved by functionalizing graphene with the strong electron acceptor, F4-TCNQ. − …”

“…In this report, we studied the F4-TCNQ-deposited bi-layer epitaxial graphene (BLG) on 6H–SiC (0001), where F4-TCNQ has been used successfully for controlled non-destructive hole doping in the graphene system, − which allows the Fermi level to shift into the energy band gap of bi-layer graphene. , Here, we explore the concentration-dependent orientation of F4-TCNQ molecules on BLG/SiC system (EG/SiC), which is coupled with the charge transfer process at the interface between the molecular electron acceptor and BLG. Molecular beam epitaxy (MBE) has been utilized to deposit the F4-TCNQ molecules on EG/SiC templates.…”