| AVS 65th International Symposium & Exhibition | |
| 2D Materials Focus Topic | Monday Sessions |
| Session 2D+MI+NS-MoA |
| Session: | 2D Materials Characterization including Microscopy and Spectroscopy |
| Presenter: | Kazu Suenaga, National Institute of Advanced Industrial Science and Technology (AIST), Japan |
| Correspondent: | Click to Email |
Two-dimensional transition metal dichalcogenides (TMDs), consisting of an atomic plane of a transition metal (M: Ti, Nb, Mo, Re, etc.) sandwiched between two chalcogen atomic planes (X: S, Se, Te). This crystalline structure combined with a wide variety of constituent elements give rise to diverse electronic properties, strongly governed by the number of its d-orbital electrons. MoS2 and WS2 are the most representative “group 6” TMDs featuring trigonal prismatic (H) phase semiconductor with a direct band gap. The TMDs can exhibit various polymorphs and present different electronic properties as the atomic arrangement changes originating from charge transfer. A metallic octahedral (T) phase has been reportedly stabilized by alkali metal intercalation [1], and another distorted octahedral phase zigzag-shape phase (Z) with clusterization of metal atoms into zigzag chains by using solvent-based exfoliation. Some simulations indicate that the Z phase may undergo the Peierls distortion and be transformed into a diamond-shape (DS) phase where atoms reconstruct in a way that four metal atom appear as a diamond (rhombus) in the plane [2]. We show in this talk the experimental evidences for these polymorphic structures and diversified properties found in a family of 2D TMDs.
These monolayer forms in TMDs are typically the same as a single layer of the bulk material. However, PdSe2 presents a puzzle. Its monolayer form has been theoretically shown to be stable, but there have been no reports that monolayer PdSe2 was fabricated. Here, we demonstrate that the preferred monolayer form of this material amounts to a melding of two bulk monolayers accompanied by the emission of Se atoms so that the resulting stoichiometry is Pd2Se3[3].
[1] Y.-C. Lin, D. O. Dumcenco, Y.-S. Huang and K. Suenaga, Nature Nanotechnology, 9 (2014) pp.391-396
[2] Y.-C. Lin, H.-P. Komsa, C.-H. Yeh, T. Bjorkman, Z.-Y. Liang, C.-H. Ho, Y.-S. Huang, P.-W. Chiu, A. V. Krasheninnikov, and K. Suenaga, ACS Nano 9 (2015) pp.11249-11257
[3] J. Lin, S. Zuluaga, P. Yu, Z. Liu, S. T. Pantelides, and K. Suenaga Phys. Rev. Lett., 119 (2017) 016101
[4] This research was supported by JSPS KAKENHI (JP16H06333 and JP25107003).