Quasi-1D TiS3 Nanoribbons: Mechanical Exfoliation and Thickness-Dependent Raman Spectroscopy

Alexey Lipatov; Michael J Loes; Haidong Lu; Jun Dai; Piotr Patoka; Nataliia S Vorobeva; Dmitry S Muratov; Georg Ulrich; Bernd Kästner; Arne Hoehl; Gerhard Ulm; Xiao Cheng Zeng; Eckart Rühl; Alexei Gruverman; Peter A Dowben; Alexander Sinitskii

doi:10.1021/acsnano.8b07703

Quasi-1D TiS₃ Nanoribbons: Mechanical Exfoliation and Thickness-Dependent Raman Spectroscopy

ACS Nano. 2018 Dec 26;12(12):12713-12720. doi: 10.1021/acsnano.8b07703. Epub 2018 Nov 30.

Authors

Alexey Lipatov¹, Michael J Loes¹, Haidong Lu², Jun Dai¹, Piotr Patoka³, Nataliia S Vorobeva¹, Dmitry S Muratov^{1

4}, Georg Ulrich^{3

5}, Bernd Kästner⁵, Arne Hoehl⁵, Gerhard Ulm⁵, Xiao Cheng Zeng^{1

6}, Eckart Rühl³, Alexei Gruverman^{2

6}, Peter A Dowben^{2

6}, Alexander Sinitskii^{1

6}

Affiliations

¹ Department of Chemistry , University of Nebraska , Lincoln , Nebraska 68588 , United States.
² Department of Physics and Astronomy , University of Nebraska , Lincoln , Nebraska 68588 , United States.
³ Physical Chemistry, Institut für Chemie und Biochemie , Freie Universität Berlin , 14195 Berlin , Germany.
⁴ National University of Science and Technology "MISIS" , Moscow 119991 , Russia.
⁵ Physikalisch-Technische Bundesanstalt (PTB) , Abbestraße 2-12 , 10587 Berlin , Germany.
⁶ Nebraska Center for Materials and Nanoscience , University of Nebraska , Lincoln , Nebraska 68588 , United States.

PMID: 30499656
DOI: 10.1021/acsnano.8b07703

Abstract

Quasi-one-dimensional (quasi-1D) materials enjoy growing interest due to their unusual physical properties and promise for miniature electronic devices. However, the mechanical exfoliation of quasi-1D materials into thin flakes and nanoribbons received considerably less attention from researchers than the exfoliation of conventional layered crystals. In this study, we investigated the micromechanical exfoliation of representative quasi-1D crystals, TiS₃ whiskers, and demonstrate that they typically split into narrow nanoribbons with very smooth, straight edges and clear signatures of 1D TiS₃ chains. Theoretical calculations show that the energies required for breaking weak interactions between the two-dimensional (2D) layers and between 1D chains within the layers are comparable and, in turn, are considerably lower than those required for breaking the covalent bonds within the chains. We also emulated macroscopic exfoliation experiments on the nanoscale by applying a local shear force to TiS₃ crystals in different crystallographic directions using a tip of an atomic force microscopy (AFM) probe. In the AFM experiments, it was possible to slide the 2D TiS₃ layers relative to each other as well as to remove selected 1D chains from the layers. We systematically studied the exfoliated TiS₃ crystals by Raman spectroscopy and identified the Raman peaks whose spectral positions were most dependent on the crystals' thickness. These results could be used to distinguish between TiS₃ crystals with thickness ranging from one to about seven monolayers. The conclusions established in this study for the exfoliated TiS₃ crystals can be extended to a variety of transition metal trichalcogenide materials as well as other quasi-1D crystals. The possibility of exfoliation of TiS₃ into narrow (few-nm wide) crystals with smooth edges could be important for the future realization of miniature device channels with reduced edge scattering of charge carriers.

Keywords: Raman spectroscopy; mechanical exfoliation; quasi-one-dimensional materials; scanning near-field optical microscopy; transition metal trichalcogenides.