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Quasi-Layer-by-Layer Growth of Pentacene on HOPG and Au Surfaces
journal contribution
posted on 2017-10-19, 00:00 authored by Hongyan Yang, Lizhen Huang, Kewei Sun, Kaifeng Niu, Zequn Cui, Haiming Zhang, Zi Wang, Donghang Yan, Lifeng ChiHigh-resolution scanning
tunneling microscopy (STM) is a promising
method for characterizing organic semiconductors to obtain a deep
understanding of organic semiconductor physics. However, organic films
on conductive single-crystal substrates, which are required for STM,
usually present different growth behaviors than the films on inert
substrates such as SiO2. Here, we reported a simple modification
method for modulating the organic semiconductor film growth on the
highly oriented pyrolytic graphite (HOPG) and Au(111) substrates and
investigated the detailed morphology evolution. Self-assembled monolayers
(SAMs) fabricated from vacuum deposition and solution processing were
introduced on these conductive substrates. Pentacene, a prototypical
organic semiconductor, presented quasi-layer-by-layer growth on HOPG
or Au(111) sufaces modified with solution-processed alkane monolayer.
The pentacene film resembled the upright packing and terraced morphology
but with larger grain size than that of thin-film phase on SiO2. The introduced n-dotriacontane layer decreased
the interaction between pentacene adsorbates and the active substrate
and provided a lower surface energy which supported the upright orientation
of pentacene. Modification of the substrates with alkanes provides
a feasible approach to grow high-quality organic thin films that are
suitable for characterization down to the molecular level. Additionally,
this approach is effective for two-dimensional substrate materials
such as graphene and is not limited to single-crystal substrates.