PdSe₂: Pentagonal Two-Dimensional Layers with High Air Stability for Electronics

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 PdSe 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 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 display tunable ambipolar charge carrier conduction with a high electron field-effect mobility of ∼158 cm V s, indicating the promise of this anisotropic, air-stable, pentagonal 2D material for 2D electronics.

Layer-dependent band engineering of Pd dichalcogenides: a first-principles study

“…Moreover, we are also able to observe a shift in the lowest point of CBM from S point to in-between S and Y points, and highest point of VBM from near Γ region to in-between Γ and X, during the transition from 1L to 2L. For comparison with experimental studies [12,19,35], the calculated band gaps (table S1) of the corresponding pyrite thin film structures are relatively in good agreement with experimental findings. Figure 4(b) shows the calculated band structures of 1T PdSe 2 from 1L to 5L thickness.…”

“…1T, 2H, and 3R [11]. Moreover, recent studies [12][13][14][15][16][17][18][19][20] have shown that some TMDs can also exhibit orthorhombic structures, specifically pyrite and marcasite structures.…”

“…Up until recently, fabrication techniques have been limited to mechanical exfoliation [12,34] and molecular beam epitaxy (MBE) [35]. These methods, however, lead to low yield and quality, and were not fit for practical applications.…”

“…These methods, however, lead to low yield and quality, and were not fit for practical applications. With the development of highly efficient fabrication techniques to synthesize TMDs by employing post-chalcogenization through sulfurization [16] or selenization [19,36], as well as the discovery of its new 2D pentagonal crystal structure [12,14], the fascination to explore Pd-based TMDs has been reawakened.…”

Striated 2D Lattice with Sub‐nm 1D Etch Channels by Controlled Thermally Induced Phase Transformations of PdSe2

“…[16][17][18][19][20] Among them, palladium diselenide (PdSe 2 ) is attracting attention due to its interesting electronic properties and atomic structure. [24,25] In contrast to the frequently reported hexagonal phases in TMDs, PdSe 2 has a unique structure, Figure 1a. [24,25] In contrast to the frequently reported hexagonal phases in TMDs, PdSe 2 has a unique structure, Figure 1a.…”