Determination of Both Tilting and In-Plane Molecular Rotational Angles for Dinaphtho[2,3-b:2’,3’-f]thieno[3,2-b]thiophene Using Near Edge X-ray Absorption Fine Structure

[ABSTRACT] We demonstrate that both the in-plane molecular rotational and the tilting angles of the molecular orientation can be determined using the σ* resonance of sulfur (S) K-edge near edge X-ray absorption fine structure. We examined dinaphtho[2,3-b:2’,3’-f]thieno[3,2-b]thiophene (DNTT) thin films on silicon dioxide (SiO2) and copper oxide (CuOx) substrates which are relevant to the cost-effective organic field-effect transistors. In-plane directed transition moments were attributed to the electron excitation from S 1s to largely overlapped σ* orbital related to the C-S bonding at the thiophene site. Under the coexistence with a minor component of the amorphous region, it turned out that the DNTT domain with the single crystal structure with the c-axis normal to the substrates; the DNTT molecules on SiO2 orient at a tilting angle (β) of 85° and an in-plane rotational angle (ΦM) of 77° and 103°. In the case of the film on CuOx, values of 84° for β, 73° and 107° for ΦM are acquired. The amount of amorphous region in the film on CuOx was larger than that on SiO2. Our approach is applicable to other sulfur-containing molecules with a small population of the lowest unoccupied molecular orbital on the S atoms.

https://opac.ll.chiba-u.jp/da/curator/900120909/

https://opac.ll.chiba-u.jp/da/curator/900120909/Kazuaki_IWASAWA_JPCC_Manuscript_revision1.pdf

American Chemical Society

Journal Article

The Journal of Physical Chemistry C

124

26

14195

14201

2020

https://doi.org/10.1021/acs.jpcc.0c02180

eng

https://doi.org/10.1021/acs.jpcc.0c02180

author

This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry C, copyright (c) 2020 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.jpcc.0c02180.