Electronic structure of biphenyl on Si(100)

Abstract

We report the study of both occupied and unoccupied electronic states of biphenyl adsorbed on Si͑100͒ by using synchrotron radiation ultraviolet photoemission spectroscopy, x-ray photoemission spectroscopy, and near-edge x-ray absorption fine structure spectroscopy. The results are compared with calculations of the occupied densities of states. Evidence is given of two main effects: ͑i͒ a down shift in energy of the second highest occupied molecular orbital of the strongly chemisorbed configuration at room temperature compared to the weakly chemisorbed configuration at low temperatures and ͑ii͒ an energy splitting of some of the occupied and unoccupied states due to the different interactions of the two phenyl rings of the molecule. The electronic structure of biphenyl on Si͑100͒ appears to be an appropriate test for state of the art experimental and theoretical methods.

Chemical manipulation of multifunctional hydrocarbons on silicon surfaces

“…A manuscript by Cranney et al reports on a detailed experimental and theoretical investigation of biphenyl on Si(100), a continuation of the work reported in this review [477]. The continuation of work on large molecules, such as 1,4 -paratriphenyldimethylacetone molecule (trima) [478] as well as an investigation of cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene (CMTE), a photochromic dye, on Si(100)-2×1 [479] is also now available.…”

Adsorption of Water and Ammonia on Graphene: Evidence for Chemisorption from X-ray Absorption Spectra

“…We use near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to examine the unoccupied region of the electronic structure . Whereas in previous NEXAFS investigations of adsorption processes − only the adsorbate electronic states were probed, we are able to study both partners in the adsorption complex, that is, the electronic structure rearrangement upon adsorption in both the adsorbate and the substrate, through K edge absorption from the carbon atoms of graphene. In X-ray absorption studies of adsorption on bulk substrates, the signal from the surface region of the substrate is generally masked by emission from deeper layers not involved in the adsorption process; here, however, the single-atom thickness of graphene (“all surface and no bulk”) permits one to identify changes induced in the substrate electronic states.…”

Uniaxial Strain in Molecular Nanowires: A Case Study of β-phase Polyfluorenes

“…The Si(100) substrate consists of a surface layer of rows of buckled Si dimers, in which the upper dimer atom has a slight negative charge and the lower atom a slight positive charge . Since the first demonstration that the unsaturated hydrocarbon molecule ethylene could adsorb via a cycloaddition reaction in which two Si−C σ bonds are formed, , other small unsaturated hydrocarbons have been attached to the Si(100) substrate. , In the case of aromatic molecules, at low coverages, experimental and computational studies show that they can adsorb intact with the molecular plane parallel to the surface plane, and distortions of the planar aromatic molecules occur as Si−C bonds are formed, breaking the aromaticity of the molecules. − In particular, one of the stable configurations of pentacene adsorbed on a Si(100) substrate has its molecular axis parallel to the Si dimer rows. − We propose the adsorption of β-phase polyfluorene with its molecular plane parallel to a silicon dimer row as a model system for inducing uniaxial strain in the backbone. The flexibility permitted in the backbone, resulting from the C−C bonds linking fluorene units, could potentially enable bonding over the extent of the polymer.…”

“…14,15 In the case of aromatic molecules, at low coverages, experimental and computational studies show that they can adsorb intact with the molecular plane parallel to the surface plane, and distortions of the planar aromatic molecules occur as Si-C bonds are formed, breaking the aromaticity of the molecules. [16][17][18][19][20][21][22][23][24] In particular, one of the stable configurations of pentacene adsorbed on a Si(100) substrate has its molecular axis parallel to the Si dimer rows. [22][23][24] We propose the adsorption of β-phase polyfluorene with its molecular plane parallel to a silicon dimer row as a model system for inducing uniaxial strain in the backbone.…”