PdSe<sub>2</sub>: Pentagonal Two-Dimensional Layers with High Air Stability for Electronics Akinola D. Oyedele Shize Yang Liangbo Liang Alexander A. Puretzky Kai Wang Jingjie Zhang Peng Yu Pushpa R. Pudasaini Avik W. Ghosh Zheng Liu Christopher M. Rouleau Bobby G. Sumpter Matthew F. Chisholm Wu Zhou Philip D. Rack David B. Geohegan Kai Xiao 10.1021/jacs.7b04865.s001 https://acs.figshare.com/articles/journal_contribution/PdSe_sub_2_sub_Pentagonal_Two-Dimensional_Layers_with_High_Air_Stability_for_Electronics/5445187 Most studied two-dimensional (2D) materials exhibit isotropic behavior due to high lattice symmetry; however, lower-symmetry 2D materials such as phosphorene and other elemental 2D materials exhibit very interesting anisotropic properties. In this work, we report the atomic structure, electronic properties, and vibrational modes of few-layered PdSe<sub>2</sub> exfoliated from bulk crystals, a pentagonal 2D layered noble transition metal dichalcogenide with a puckered morphology that is air-stable. Micro-absorption optical spectroscopy and first-principles calculations reveal a wide band gap variation in this material from 0 (bulk) to 1.3 eV (monolayer). The Raman-active vibrational modes of PdSe<sub>2</sub> were identified using polarized Raman spectroscopy, and a strong interlayer interaction was revealed from large, thickness-dependent Raman peak shifts, agreeing with first-principles Raman simulations. Field-effect transistors made from the few-layer PdSe<sub>2</sub> display tunable ambipolar charge carrier conduction with a high electron field-effect mobility of ∼158 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>, indicating the promise of this anisotropic, air-stable, pentagonal 2D material for 2D electronics. 2017-09-05 00:00:00 2 D materials exhibit transition metal dichalcogenide thickness-dependent Raman peak shifts lower-symmetry 2 D materials band gap variation few-layer PdSe 2 display tunable ambipolar charge carrier conduction 2 D electronics few-layered PdSe 2 exfoliated first-principles Raman simulations anisotropic High Air Stability air-stable bulk electron field-effect mobility Raman-active vibrational modes spectroscopy pentagonal 2 D pentagonal 2 D material Pentagonal Two-Dimensional Layers PdSe 2