Adsorption of 1,3,5-Triphenylbenzene Molecules and Growth of Graphene Nanoflakes on Cu(100)Surface

Adsorption of 1,3,5-triphenylbenzene(TPB) molecules on Cu( 100) surface is studied using ultraviolet photoelectron spectroscopy(UPS) and density functional theory(DFT) calculations. Researches on the bottom-up fabrication of graphene nanoflakes(GNFs) with TPB as a precursor on the Cu(100) surface are carried out based on UPS and DFT calculations. Three emission features d, e and f originating from the TPB molecules are located at 3.095, 7.326 and 9.349 eV below the Fermi level, respectively. With the increase of TPB coverage on the Cu(100) substrate, the work function decreases due to the formation of inter facial dipoles and charge(electron)rearrangement at the TPB/Cu(100) interface. Upon the formation of GNFs, five emission characteristic peaks of g, h, i, j and k originating from the GNFs are located at 1.100, 3.529, 6.984, 8.465 and 9.606 eV below the Fermi level, respectively. Angle resolved ultraviolet photoelectron spectroscopy(ARUPS) and DFT calculations indicate that TPB molecules adopt a lying-down configuration with their molecular plane nearly parallel to the Cu(100) substrate at the monolayer stage. At the same time, the lying-down configuration for the GNFs on the Cu(100) surface is also unveiled by ARUPS and DFT calculations.

Adsorption behavior of triphenylene on Ru(0001) investigated by scanning tunneling microscopy

As a representative of small aromatic molecules, triphenylene(TP) has markedly high carrier mobility and is an ideal precursor for building graphene nanostructures. We mainly investigated the adsorption behavior of TP molecules on Ru(0001) by using scanning tunneling microscopy(STM). In submonolayer regime, TP molecules are randomly dispersed on Ru(0001) and the TP overlayer can be thoroughly dehydrogenated and converted into graphene islands at 700 K. Due to weak interaction between TP molecules and graphene, the grooves formed among graphene islands have confinement effect on TP molecules. TP adopts a flat-lying adsorption mode and has two adsorption configurations with the 3-fold molecular axis aligned almost parallel or antiparallel to the ■ direction of the substrate. At TP coverages of 0.6 monolayer(ML)and 0.8 ML, the orientational distributions of the two adsorption configurations are equal. At about 1.0 ML, we find the coexistence of locally ordered and disordered phases. The ordered phase includes two sets of different superstructures with the symmetries of ■R23.41° and p(4 × 4), respectively. The adsorption behavior of TP on Ru(0001) can be attributed to the delicate balance between molecule–substrate and molecule–molecule interactions.

Triphenylene adsorption on Cu(111) and relevant graphene self-assembly

Investigations on adsorption behavior of triphenylene(TP)and subsequent graphene self-assembly on Cu(111)were carried out mainly by using scanning tunneling microscopy(STM).At monolayer coverage,TP molecules formed a long-range ordered adsorption structure on Cu(111)with an uniform orientation.Graphene self-assembly on the Cu(111)substrate with TP molecules as precursor was achieved by annealing the sample,and a large-scale graphene overlayer was successfully captured after the sample annealing up to 1000 K.Three different Moirépatterns generated from relative rotational disorders between the graphene overlayer and the Cu(111)substrate were observed,one with 4°rotation between the graphene overlayer and the Cu(111)substrate with a periodicity of 2.93 nm,another with 7°rotation and 2.15 nm of the size of the Moirésupercell,and the third with 10°rotation with a periodicity of 1.35 nm.