The Molecular Orientation of para‐Sexiphenyl on Cu(110) and Cu(110) p(2×1)O

Abstract

Controlling the molecular growth of organic semiconductors is an important issue to optimize the performance of organic devices. Conjugated molecules, used as building blocks, have an anisotropic shape and also anisotropic physical properties like charge transport or luminescence. The main challenge is to grow highly crystalline layers with molecules of defined orientation. The higher the crystallinity, the closer these properties reach their full intrinsic potential, while the orientation determines the physical properties of the film. Herein we show that the molecular orientation and growth can be steered by the surface chemistry, which tunes the molecule-substrate interaction. In addition, the oxygen reconstruction of the surface, demonstrates the flexibility of the organic molecules to adopt a given surface corrugation and their unique possibility to release stress by tilting.

Epitaxial growth of sexithiophene on (110)

“…Our growth model is that initially adsorbed molecules are adsorbed edge-on, aligned along the oxygen rows, which is a manner similar to that of 6T and 6P on Cu-O and 5T on TiO 2 [11,33,12]. This type of alignment is already promoting the contact plane 6T{0 1 0}.…”

Uniform π‐System Alignment in Thin Films of Template‐Grown Dicarbonitrile‐Oligophenyls

“…A uniform azimuthal orientation can be imposed on the thin fi lm by rubbing a precursor layer linearly [ 8 ] or by growth on anisotropic substrates. [9][10][11] In contrast, no effi cient ways to control the rotation of the molecular plane (defi ned as the reference plane later on in the text) around the long molecular axis are known. In the bulk, the planes of two neighboring molecules include an angle of 66 ° , [12][13][14] an arrangement further referred to as the herringbone ordering.…”

“…[ 22 , 23 ] For molecules with stronger intermolecular forces due to functional groups like perylenetetracarboxylic-dianhydride [ 24 ] or biphenyl-oxalic amide, [ 25 ] the transition to the bulk ordering takes place even faster. The use of strongly corrugated substrates such as Cu(110) and its oxygen-covered variant allowed controlling the azimuthal alignment of sexithiophene [ 26 ] and the afore mentioned sexiphenyl, [ 9 ] but in both cases only minor changes to the bulk-like ordering could be achieved in the thin fi lms. Only in rare cases did the substrate-induced ordering persist in multilayer fi lms.…”

Two-Dimensional Nanotemplates as Surface Cues for the Controlled Assembly of Organic Molecules

“…The same system has been used to study the electronic properties and the Reprinted with permission from [132]. © (2004) Wiley self assembly of oligophenylenes by means of ultraviolet photoelectron spectroscopy (UPS) [137] STM and NEXAFS [138] and, in a different context, to study adsorbate-induced surface stress [139].…”