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Title: Orientation-dependent energy level alignment and film growth of 2,7-diocty[1]benzothieno[3,2-b]benzothiophene (C8-BTBT) on HOPG

Combining ultraviolet photoemission spectroscopy, X-ray photoemission spectroscopy, atomic force microscopy, and X-ray diffraction measurements, we performed a systematic investigation on the correlation of energy level alignment, film growth, and molecular orientation of 2,7-diocty[1]benzothieno[3,2-b]benzothiophene (C8-BTBT) on highly oriented pyrolytic graphite. The molecules lie down in the first layer and then stand up from the second layer. The ionization potential shows a sharp decrease from the lying down region to the standing up region. When C8-BTBT molecules start standing up, unconventional energy level band-bending-like shifts are observed as the film thickness increases. These shifts are ascribed to gradual decreasing of the molecular tilt angle about the substrate normal with the increasing film thickness.
Authors:
; ; ; ; ; ;  [1] ;  [2] ;  [1] ;  [2] ;  [3]
  1. Institute of Super-Microstructure and Ultrafast Process in Advanced Materials, School of Physics and Electronics, Central South University, No. 605 Lushan South Road, Changsha, Hunan 410012 (China)
  2. (China)
  3. (United States)
Publication Date:
OSTI Identifier:
22493670
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 144; Journal Issue: 3; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ATOMIC FORCE MICROSCOPY; CORRELATIONS; ENERGY LEVELS; FILMS; GRAPHITE; LAYERS; MOLECULES; ORIENTATION; PHOTOELECTRON SPECTROSCOPY; POTENTIALS; SUBSTRATES; THIONAPHTHENES; THIOPHENE; ULTRAVIOLET RADIATION; X-RAY DIFFRACTION