Thermo-controllable self-assembled structures of single-layer 4, 4"-diamino-p-terphenyl molecules on Au (110)

Here we report the thermo-controllable self-assembled structures of single-layer 4, 4"-diamino-p-terphenyl (DAT) molecules on Au (110), which are investigated by scanning tunneling microscopy (STM) combined with density functional theory (DFT) based calculations. With the deposition of monolayer DAT molecules on Au (110) and subsequent annealing at 100 ℃, all DAT molecules adsorb on a (1×5) reconstructed surface with a ladder-like structure. After annealing the sample at about 200 ℃, STM images show three distinct domains, including DAT molecules on a (1×3) reconstructed surface, dehydrogenated molecules with two hydrogen atoms detached from one amino group (-2H-DAT) on a (1×5) reconstructed surface and dehydrogenated molecules with four hydrogen atoms detached from two amino groups (-4H-DAT) on a (1×3) reconstructed surface through N-Au bonds. Furthermore, after annealing the sample to 350 ℃, STM image shows only one self-assembled structure with -4H-DAT molecules on a (1×3) reconstructed surface. Relative STM simulations of different self-assembled structures show excellent agreements with the experimental STM images at different annealing temperatures. Further DFT calculations on the dehydrogenation process of DAT molecule prove that the dehydrogenation barrier on a (1×5) reconstructed surface is lower than that on (1×3) one, which demonstrate the experimental results that the formation temperature of a (1×3) reconstructed surface is higher than that of a (1×5) one.