Engineering the Structural and Electronic Phases of MoTe 2 through W Substitution

• Published in: Nano letters 2017-03, Vol.17 (3), p.1616-1622
• Main Authors: Rhodes, D, Chenet, D A, Janicek, B E, Nyby, C, Lin, Y, Jin, W, Edelberg, D, Mannebach, E, Finney, N, Antony, A, Schiros, T, Klarr, T, Mazzoni, A, Chin, M, Chiu, Y-C, Zheng, W, Zhang, Q R, Ernst, F, Dadap, J I, Tong, X, Ma, J, Lou, R, Wang, S, Qian, T, Ding, H, Osgood, Jr, R M, Paley, D W, Lindenberg, A M, Huang, P Y, Pasupathy, A N, Dubey, M, Hone, J, Balicas, L
• Format: Article
• Language: English
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.6b04814

MoTe is an exfoliable transition metal dichalcogenide (TMD) that crystallizes in three symmetries: the semiconducting trigonal-prismatic 2H- or α-phase, the semimetallic and monoclinic 1T - or β-phase, and the semimetallic orthorhombic γ-structure. The 2H-phase displays a band gap of ∼1 eV making it appealing for flexible and transparent optoelectronics. The γ-phase is predicted to possess unique topological properties that might lead to topologically protected nondissipative transport channels. Recently, it was argued that it is possible to locally induce phase-transformations in TMDs, through chemical doping, local heating, or electric-field to achieve ohmic contacts or to induce useful functionalities such as electronic phase-change memory elements. The combination of semiconducting and topological elements based upon the same compound might produce a new generation of high performance, low dissipation optoelectronic elements. Here, we show that it is possible to engineer the phases of MoTe through W substitution by unveiling the phase-diagram of the Mo W Te solid solution, which displays a semiconducting to semimetallic transition as a function of x. We find that a small critical W concentration x ∼ 8% stabilizes the γ-phase at room temperature. This suggests that crystals with x close to x might be particularly susceptible to phase transformations induced by an external perturbation, for example, an electric field. Photoemission spectroscopy, indicates that the γ-phase possesses a Fermi surface akin to that of WTe .