Thickness dependent electronic properties of Pt dichalcogenides

Abstract

Platinum-based transition metal dichalcogenides have been gaining renewed interest because of the development of a new method to synthesize thin film structures. Here, using first-principles calculation, we explore the electronic properties of PtX 2 (X = S, Se, and Te) with respect to film thickness. For bulk and layered structures (1 to 10 layers), octahedral 1T is the most stable. Surprisingly, we also find that the 3R structure has comparable stability relative to the 1T, implying possible synthesis of 3R. For a bulk 1T structure, PtS 2 is semiconducting with an indirect band gap of 0.25 eV, while PtSe 2 and PtTe 2 are both semi-metallic. Still, all their corresponding monolayers exhibit an indirect semiconducting phase with band gaps of 1.68, 1.18, and 0.40 eV for PtS 2 , PtSe 2 , and PtTe 2 , respectively. For the band properties, we observe that all these materials manifest decreasing/closing of indirect band gap with increasing thickness, a consequence of quantum confinement and interlayer interaction. Moreover, we discover that controlling the thickness and applying strain can manipulate van Hove singularity resulting to high density of states at the maximum valence band. Our results exhibit the sensitivity and tunability of electronic properties of PtX 2 , paving a new path for future potential applications.

Interlayer dielectric function of a type-II van der Waals semiconductor: The HfS2/PtS2 heterobilayer

“…Such interaction produces large distortions of the valence band, which now presents two clear quasi-degenerate VBM near Γ along the Γ-M and Γ-K directions. In fact a closer inspection reveals that the VBM is formed by a set of kpoints arranged arranged along a hexagon at the edge of the 2D Brillouin zone, a fact already observed before [30].…”

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

“…The bands with the flat features in 1T PdTe 2 ( figure 6(d)), however, is positioned relatively below the Fermi level. Nevertheless, the location of the flat band can be manipulated through strain [21] to tune the vHs for monolayer 1T PdTe 2 . Focusing on PdS 2 and PdSe 2 , the flat peaks bands observed are within the VBM.…”

“…Studies have also demonstrated that the electronic properties of TMDs can easily be engineered and manipulated by tuning its thickness [21][22][23] or introduction of strain [21,[24][25][26][27], in which some of the observed phenomena were increasing and indirect-to-direct transition of band gap from bulk to monolayer, and tuning of van Hove singularity (vHs) [28] near the Fermi level. Because of these unique properties, TMDs are now one of the fascinating prospects in condensed matter research, especially in 2D materials.…”

Electronic and structural characterisation of polycrystalline platinum disulfide thin films

“…20,21 One member of the NTMD group is platinum disulde (PtS 2 ), of which ultrathin lms have recently been synthesised. [22][23][24] Theoretical and experimental studies have revealed that the size of the bandgap in PtS 2 decreases with increasing lm thickness, [23][24][25][26] going from $1.7 eV for monolayer PtS 2 to $0.25 eV for the bulk state. Indirect bandgaps were observed for all layer thicknesses as opposed to MoS 2 and WS 2 where the monolayer forms possess a direct bandgap.…”