Investigations of long-chain hydrocarbon and substituted hydrocarbon materials physisorbed at the liquid−solid interface have provided a particularly fruitful area of investigation for the scanning tunneling microscope (STM). Studies of this kind provide considerable information concerning surface−adsorbate interactions, the nature of the STM contrast mechanism for molecules adsorbed on surfaces, the effect of the chemical nature of the liquid solvent on the rearrangement and bonding of adsorbates, and the role played by the underlying structure of the surface itself (defects, domains, etc.) in determining the molecular arrangement of these adsorbates. All of these studies are aimed at the elucidation and control of surface and adsorbate structures and their relationship to the electronic and chemical properties of materials. The successful imaging of numerous physisorbed organic films at the solution−solid interface has demonstrated that the STM is sensitive enough to differentiate chemical functional gr...

STM Investigations of Organic Molecules Physisorbed at the Liquid−Solid Interface

Thin and ultra-thin films of nickel phthalocyanine grown on highly oriented pyrolitic graphite: an XPS, UHV-AFM and air tapping-mode AFM study

A series of alkyl- and alkoxy-substituted rhombic-shaped bisDBA derivatives 1a−d, 2a, and 2b were synthesized for the purpose of the formation of porous networks at the 1,2,4-trichlorobenzene (TCB)/graphite interface Depending on the alkyl-chain length and the solute concentration, bisDBAs exhibit five network structures, three porous structures (porous A, B, and C), and two nonporous structures (nonporous D and E), which are attributed to their rhombic core shape and the position of the substituents BisDBAs 1a and 1b with the shorter alkyl chains favorably form a porous structure, whereas bisDBAs 1c and 1d with the longer alkyl chains are prone to form nonporous structures However, upon dilution, nonporous structures are typically transformed into porous ones, a trend that can be understood by the effect of surface coverage, molecular density, and intermolecular interactions on the system’s enthalpy Furthermore, porous structures are stabilized by the coadsorption of solvent molecules The most intri

2D networks of rhombic-shaped fused dehydrobenzo[12]annulenes: structural variations under concentration control.

Resonance and Environmental Fluctuation Effects in STM Currents through Large Adsorbed Molecules

STM and STS investigation of ultrathin tin phthalocyanine layers adsorbed on HOPG(0001) and Au(111)

Adsorbed molecules of copper phthalocyanine (CuPc) and liquid crystals on graphite were measured by scanning tunneling microscopy (STM) and spectroscopy (STS) in air. The islands of molecules of CuPc were detected by STM. Tunneling spectra taken simultaneously with STM showed characteristic peaks correlated with local topographic features. In the observation of a nematic liquid crystal on graphite, one reproducible molecular pattern was found, for which a model of molecular ordering is proposed. Ordinary spectroscopy was found to be difficult due to a large polarization current caused by the liquid surrounding the tip. Bias voltage dependent images of the molecules which demonstrate electronic structure effects were obtained.

S. Tanishima

Papers

Scanning tunneling spectroscopy study of adsorbed molecules