Abstract
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 PdSe2 isolated 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 ~0.2 eV (bulk) to ~1.3 eV (monolayer). The Raman active vibrational modes of PdSe2 were identified using polarized Raman spectroscopy and the strong interlayer interaction was revealed from the large thickness-dependent Raman peak shifts, which agree with first-principles Raman simulations. Field-effect transistors made from the few-layer PdSe2 display tunable ambipolar charge carrier conduction with high electron mobility of ~ 158 cm2V-1s-1, indicating the promise of this anisotropic, air-stable, pentagonal 2D material for 2D electronics.
