Conformation, packing, defects, and molecular dynamics in monolayers of dialkyl-substituted benzenes

Journal Article · · Journal of Vacuum Science and Technology. B, Microelectronics Processing and Phenomena; (United States)

DOI:https://doi.org/10.1116/1.585230· OSTI ID:5228294

Buchholz, S; Rabe, J P ^[1]

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1. Max-Planck-Inst. fuer Polymerforschung, Mainz (Germany)

Monolayers of the two homologues dihexadecylbenzene and didodecylbenzene were adsorbed at the interface between highly oriented pyrolytic graphite (HOPG) and an organic solution. The derivatization of a small molecule, in this case benzene, with long alkyl sidechains is shown to be a method to immobilize various molecular entities at the interface between HOPG and an organic solution. This paper reports on in situ scanning tunneling microscopy (STM) studies at the internal interface revealing that the first adsorbed monolayer of the dialkyl-substituted benzenes exhibits a lamellar phase with the molecules extended and oriented parallel to the basal plane of graphite. Bias-dependent experiments allowed to either image preferentially the underlying substrate (at low bias) or the molecular adsorbate (at higher bias), without disrupting the adsorbate layer. From such experiments it was concluded that the alkane sidechains tend to orient parallel to a graphite lattice axis. High resolution images revealed different types of packing within a lamella, which were separated by sharp domain boundaries. Also packing defects involving individual molecules were observed. Most interesting, fast image recording on video tape allowed to directly follow the dynamics of such individual defects on the time scale between 100 ms and several minutes, i.e., the relevant timescale for the slow dynamics in crystalline organic phases.

• OSTI ID: 5228294
• Journal Information: Journal of Vacuum Science and Technology. B, Microelectronics Processing and Phenomena; (United States), Vol. 9:2; ISSN 0734-211X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BENZENE
ADSORPTION
CRYSTAL STRUCTURE
GRAPHITE
SORPTIVE PROPERTIES
DEFECTS
MICROSCOPY
MOLECULAR STRUCTURE
SUBSTRATES
AROMATICS
CARBON
ELEMENTAL MINERALS
ELEMENTS
HYDROCARBONS
MINERALS
NONMETALS
ORGANIC COMPOUNDS
SORPTION
SURFACE PROPERTIES
360602* - Other Materials- Structure & Phase Studies
360606 - Other Materials- Physical Properties- (1992-)