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Visualization of molecular packing and tilting domains and interface effects in tetracene thin films on H/Si(001)
Author(s) -
Tersigni Andrew,
Sadowski Jerzy T.,
Qin XiaoRong
Publication year - 2017
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201600777
Subject(s) - tetracene , materials science , monolayer , thin film , condensed matter physics , anisotropy , crystallography , low energy electron microscopy , chemical physics , lattice (music) , nanotechnology , molecule , electron microscope , chemistry , optics , physics , organic chemistry , acoustics
Visualizing molecular crystalline domains and influence of substrate defects are important in understanding the charge transport in organic thin film devices. Vacuum evaporated tetracene films of four monolayers on hydrogen‐terminated Si(001)‐2 × 1 substrate, as a prototypical system, have been studied with ex situ atomic force microscopy (AFM), transverse shear microscopy (TSM), friction force microscopy (FFM), and low‐energy electron microscopy (LEEM). Two differently oriented in‐plane lattice domains are found due to the symmetry of the substrate lattice, with no visible azimuthal twist between adjacent molecular layers in surface islands, indicating significant bulk‐like crystallization in the film. Meanwhile, two types of subdomains are observed inside of each in‐plane lattice domain. The subdomains are anisotropic in shape, and their sizes and distribution are highly influenced by the substrate atomic steps. TSM and FFM measurements indicate that these subdomains result from molecule‐tilt orderings within the bulk‐like lattice domains. TSM evidently shows a sensitivity to probe vertical molecule‐tilt anisotropy for the molecular crystals, in addition to its known ability to map the lateral lattice orientations.