Thickness dependent electronic properties of Pt dichalcogenides

By R. Villaos, C. Crisostomo, Zhi-Quan Huang, Shin-Ming Huang, A. A. Padama, Marvin A. Albao, Hsin‐Dong Lin, F. Chuang. npj 2D Materials and Applications, 2019

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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 PtX2 (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, PtS2 is semiconducting with an indirect band gap of 0.25 eV, while PtSe2 and PtTe2 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 PtS2, PtSe2, and PtTe2, 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 PtX2, paving a new path for future potential applications.First-principles calculations: electronic properties of Pt-based dichalcogenidesLayered Pt-based dichalcogenides possess thickness-dependent electronic band structures. A team led by Feng-Chuan Chuang at National Sun Yat-Sen University performed first-principles calculations to investigate the interplay between thickness and electronic properties of PtX2 dichalcogenides, where X = S, Se, and Te. In bulk PtX2, the most stable configuration was found to be 1T, although the metastable 3R structure had comparable formation energy, indicating that both 1T and 3R polytypes could be synthesized experimentally. To explore the thickness-dependent properties of PtX2, bulk lattice constants were used to construct the layered structures from monolayer up to ten layers, followed by crystal structure relaxations, and it was consistently found that the electronic band gap decreases as the number of layers increases. Furthermore, PtS2 possesses diverging density of states, indicative of possible presence of van Hove singularities.

Subfields: Electrical and Electronic Engineering, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/c0c981e4196d116b4d38d63397b289d95b5c86b9