The growth of sulfur adlayers on Au(100).

We have studied the growth of S layers adsorbed on Au(100) with low-energy electron diffraction (LEED), X-ray photoemission spectra (XPS), and scanning tunneling microscope (STM). Three phases of S/Au(100)-(2 × 2), trimer, and c(2 × 4)-are identified; the latter two are not previously reported. A dose of S2 at 300 K transformed Au(100)-(5 × 20) initially into the (2 × 2) phase and formed the c(2 × 4) phase at a saturation coverage. The STM results show that monolayer Au islands formed during the initial S dose and remained throughout the growth, resulting in a rough c(2 × 4) surface. We show that a highly ordered c(2 × 4) phase can be obtained with a flat (2 × 2) phase as an intermediate step during growth. Based on the evolution of XPS and STM images with varied S2 dose, the components of S 2p are assigned and structural models for the various S/Au(100) phases are proposed. In the (2 × 2) phase, one S atom resides on a four-fold hollow site in each (2 × 2) unit cell, corresponding to a S coverage of 0.25 ML; in the trimer phase, three S atoms form a trimer residing on a four-fold hollow site in each (2 × 2) unit cell, corresponding to a S coverage of 0.75 ML; in the c(2 × 4) phase, there are five S atoms in each primitive unit cell of c(2 × 4); three of them form a trimer residing on a four-fold hollow site, and the other two form a dimer located on the top of the trimer, corresponding to a nominal S coverage of 1.25 ML. With the proposed structural models, the growth of S on Au(100) at 300 K is described in detail.

Benzo[1,2-b:4,5-b']dithiophene-based cruciforms: syntheses, crystal structures, and charge transport properties.

Cruciform compound, 2,6-bis(phenylethynyl)-4,8-bis(phenylethynyl)benzo[1,2-b:4,5-b']dithiophene and its alkyl substituted derivatives, 1a-d, were designed and synthesized. Their physicochemical properties were studied by thermogravimetric analysis, absorption spectra, and cyclic voltammetry. Single crystal diffraction results revealed that 1a-d adopted different molecular packing in the solid state, which was caused by the introduction and the different orientations of alkyl chains. The single micrometer ribbon transistors of 1a displayed high mobility up to 0.81 cm(2) V(-1) s(-1). And the as-spun thin film transistors of 1c exhibited mobility as high as 0.106 cm(2) V(-1) s(-1), 2 orders of magnitude higher than those of 1b (0.006 cm(2) V(-1) s(-1)) and 1d (0.002 cm(2) V(-1) s(-1)).

N-acylation: an effective method for reducing the LUMO energy levels of conjugated polymers containing five-membered lactam units.

N-acylation was studied as a method for reducing the LUMO energy levels of benzodipyrrolidone-based polymers. The N-acylated polymers showed reduced LUMO levels and improved reversibility of reductive doping compared with N-alkylated polymers. This method may also apply in other conjugated polymers with lactam repeating units.