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HL: Fachverband Halbleiterphysik
HL 13: Poster Session I
HL 13.2: Poster
Montag, 12. März 2018, 17:30–19:30, Poster B
First Principles Phase Diagram Calculations for the 2D TMD systems MoS2−MoTe2 and WS2−WTe2. — •Benjamin Burton — Materials Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, USA
First Principles Phase Diagram Calculations were performed for the 2D Transition Metal Dichalcogenide Systems MoS2−MoTe2 and WS2−WTe2. These FPPD calculations were performed with the ATAT system using VASP calculated formation energies for MS2−2xTe2x supercells (M=Mo or W) as input. For both of these systems, very surprising results were obtained: (1) although all calculated formation energies for systems with 16 or fewer anion sites were positive, suggesting a miscibility gap, entropy stabilized intermediate phases were predicted in Mo(S,Te)2; (2) although one expects immiscibility to be greater on the S-rich sides of these diagrams (because S2− is a smaller ion than Te2−) it is much greater on the Te-rich sides.This surprising asymmetry is understood as reflecting a preponderance of lower-energy metastable ordered states on the S-rich sides of the systems.
The calculated phase diagrams are for bulk systems, but results for monolayers of Mo(S,Te)2 on a saphire substrate [Al-terminated, (0001) face] will also be discussed.