Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) ere performed on monolayer film of NiTPP supported on Au(111) under ultrahigh vacuum (UHV) conditions. The constant current STM images show remarkable bias dependence. High resolution STM data clearly show the individual NiTPP molecules and allow easy differentiation between NiTPP and CoTPP reported before. Scanning tunneling spectra, as a function of molecule-tip separation, were acquired over a range of tip motion of 0.42 nm. Spectra do not show the variation in band splitting with tip distance. It appears for molecules such as NiTPP that the average potential at the molecule is essentially the same at the same metal substrate. For molecules of the height of NiTPP, the scanning tunneling spectra should give reliable occupied and unoccupied orbital energies over a wide range of tipmolecule distances.

Orbital-mediated tunneling spectra obtained in the STM environment are reported for nickel(II) tetra-phenylporphyrin, NiTPP, as a function of molecule-tip separation. Spectra were acquired over a range of tip motion of 0.42 nm. Spectra did not show the variation in band splitting with tip distance predicted by several models. It appears for molecules such as NiTPP that the average potential at the molecule is essentially the same as at the metal substrate, at least for gap resistance values greater than 500 M

An ultrahigh-vacuum scanning tunneling microscopy equipped with a conductive optical fiber tip and photon detector has been established to explore photon emission from a self-assembled monolayer (SAM) of Cu-tetra-[3,5-di-t-butylphenyl] porphyrin (Cu-TBPP) molecules on a Cu(100) surface. In a few nanometer scale areas, emitted photons from molecules induced by tunneling electrons were effectively collected within the near-field region through an apex of the conductive optical fiber tip. The photon emission can be attributed to the inelastic tunneling involving the optical fiber tip, the Cu-TBPP molecules, and the Cu~100! surface. We proposed two kinds of mechanisms in terms of the photon emission from a SAM of Cu-TBPP molecules on a Cu(100) surface. The quantum efficiency for molecular fluorescence induced by inelastic tunneling can be approximately estimated to be ;3.031026 photons per electron in the current experimental studies.

Double-ended alkanedithiols, 1,9-nonanedithiol and 1,5-pentanedithiol, formed self-assembled monolayers (SAMs) on Au(l11) substrates and were used to adsorb silver ions from an ethanolic solution of silver nitrate and formed Ag–dithiol–Au multilayer structures. Ellipsometry, contact angle measurement and X-ray photoelectron spectroscopy (XPS) confirmed that the alkanedithiol molecules formed SAMs with only one-ended thiol groups attached to the Au substrates, which was supported by molecular mechanics calculation. XPS and X-ray Auger electron spectroscopy (XAES) indicated that silver ions were deposited onto the SAMs from the solution by the chemical reaction of silver nitrate with another-ended thiol groups of the SAMs. Atomic force microscopy (AFM) was used to observe SAMs and multilayer structures.

Self-assembled monolayers (SAMs) of 1,5-pentanedithiol and 1,9-nonanedithiol on Au (111) surfaces were used to adsorb copper ions (Cu2C) from an ethanolic solution of cupric chloride (CuCl2) by chemical interaction of thiol groups and copper ions assembling multilayer structures. Ellipsometry, contact angle measurement and X-ray photoelectron spectroscopy (XPS) confirmed that the alkanedithiol molecules formed SAMs with only one-ended thiol groups attached to the gold surface, leaving the other-ended thiol groups free, which is supported by the molecular mechanics calculation. XPS and X-ray Auger electron spectroscopy (XAES) not only indicate that copper ions deposited onto SAMs from the solution by the chemical reaction of copper ions with ended free thiol groups of SAMs, but more importantly demonstrate that copper is present in the C1 oxidation state in the multilayer system. Atomic force microscopy (AFM) was used to observe SAMs and multilayer structures.