Subscriber access provided by KEAN UNIV
C: Surfaces, Interfaces, Porous Materials, and Catalysis
Well-Ordered Monolayer Growth of Crown-Ether Ring Molecules on Cu(111) in Ultra-High Vacuum: A STM, UPS, and DFT Study Ryohei Nemoto, Peter Krueger, Ayu Novita Putri Hartini, Takuya Hosokai, Masaki Horie, Satoshi Kera, and Toyo Kazu Yamada J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.9b03335 • Publication Date (Web): 15 Jul 2019 Downloaded from pubs.acs.org on July 20, 2019
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
The Journal of Physical Chemistry
Well-Ordered Monolayer Growth of Crown-Ether Ring Molecules on Cu(111) in Ultra-High Vacuum: A STM, UPS, and DFT Study Ryohei Nemoto1, Peter Krüger1,2, Ayu Novita Putri Hartini1, Takuya Hosokai3, Masaki Horie4, Satoshi Kera1,5, and Toyo Kazu Yamada1,2* 1. Department of Materials Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan. 2. Molecular Chirality Research Center, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan. 3. National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan. 4. Department of Chemical Engineering, National Tsing Hua University, 101, Sec. 2, Kuang-Fu Road, Hsinchu, 30013, Taiwan. 5. Institute for Molecular Science, Myodaiji, Okazaki 444-8585 Japan.
ABSTRACT: Crown-ether (CR) ring molecules are known as host molecules for capturing guest species inside the ring. So far CR molecular films have only been grown by drop-casting a CR solution on an inert substrate in air which offers little control over the molecular structure. Here we report the successful growth of a well-ordered CR molecular array on an atomically-flat and clean noble metal Cu(111) substrate at 300 K in UHV, using 4,4’,5,5’-tetrabromodibenzo[18] crown-6 ether (BrCR). The adsorption, self-assembly and electronic structures of Br-CR were studied by means of UHV lowtemperature scanning tunneling microscopy (STM) and spectroscopy (STS), low electron energy diffraction (LEED), and angle-resolved ultraviolet photoemission spectroscopy (UPS). We find that (1) the Br-CR ring, which is bent both in the crystal and gas phase, flattens upon adsorption on Cu(111). Density functional theory (DFT) reveals that the two benzene groups of the molecule lie flat on the surface such as to maximize the substrate-molecule interaction. (2) The moderate molecule-substrate interaction allows thermal diffusion of the Br-CR molecules, resulting in the formation of self-assembled monolayer islands with 7×4 superstructure. (3) While the deposition of 0.05 ML Br-CR forms multi-domain islands with disordered defects, a drastic improvement occurred at 0.25 ML, where only atomically flat single-domain islands were grown. This Br-CR flat ring cavity array could become a template for designing novel two-dimensional arrays of desired guest atoms, ions, or functionalized molecules.
1. Introduction The growth of organic films by molecular evaporation and deposition on atomically clean substrates in ultrahigh vacuum (UHV) has been studied intensively in the last decades.1-16 UHV growth has several advantages with respect to chemical growth methods such as drop-casting a molecular solution on the substrate in air.1720
First, contamination of the film with solvent residue, a common problem with solution-based processes,
is excluded in UHV. Second, the formation of well-ordered molecular arrays can be controlled more easily
ACS Paragon Plus Environment
The Journal of Physical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 2 of 28
in molecular beam epitaxy under UHV conditions, because of the cleanliness of the substrate and control of deposition rate and substrate temperature. As a consequence, molecular films grown in UHV contain much less defects due to impurities, improving the molecular crystallinity, electronic properties and thus the device quality.21 Since atomically-flat and clean (impurity
