skip to main content

SciTech ConnectSciTech Connect

Title: Rich structural phase diagram and thermoelectric properties of layered tellurides Mo{sub 1−x}Nb{sub x}Te{sub 2}

MoTe{sub 2} is a rare transition-metal ditelluride having two kinds of layered polytypes, hexagonal structure with trigonal prismatic Mo coordination and monoclinic structure with octahedral Mo coordination. The monoclinic distortion in the latter is caused by anisotropic metal-metal bonding. In this work, we have examined the Nb doping effect on both polytypes of MoTe{sub 2} and clarified a structural phase diagram for Mo{sub 1−x}Nb{sub x}Te{sub 2} containing four kinds of polytypes. A rhombohedral polytype crystallizing in polar space group has been newly identified as a high-temperature metastable phase at slightly Nb-rich composition. Considering the results of thermoelectric measurements and the first-principles calculations, the Nb ion seemingly acts as a hole dopant in the rigid band scheme. On the other hand, the significant interlayer contraction upon the Nb doping, associated with the Te p-p hybridization, is confirmed especially for the monoclinic phase, which implies a shift of the p-band energy level. The origin of the metal-metal bonding in the monoclinic structure is discussed in terms of the d electron counting and the Te p-p hybridization.
Authors:
;  [1] ;  [1] ;  [2] ;  [1] ;  [3]
  1. Department of Applied Physics, University of Tokyo, Hongo, Tokyo 113-8656 (Japan)
  2. (CEMS), Wako, Saitama 351-0198 (Japan)
  3. (Japan)
Publication Date:
OSTI Identifier:
22415277
Resource Type:
Journal Article
Resource Relation:
Journal Name: APL materials; Journal Volume: 3; Journal Issue: 4; Other Information: (c) 2015 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ANISOTROPY; CONCENTRATION RATIO; ELECTRONIC STRUCTURE; ELECTRONS; ENERGY LEVELS; HOLES; MOLYBDENUM TELLURIDES; MONOCLINIC LATTICES; NIOBIUM IONS; PHASE DIAGRAMS; THERMOELECTRIC PROPERTIES; TRIGONAL LATTICES