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Proceedings Paper

Semiconductor-to-metal phase change in MoTe2 layers (Conference Presentation)
Author(s): Albert V. Davydov; Sergiy Krylyuk; Irina Kalish; Louisa Meshi; Ryan Beams; Berc Kalanyan; Deepak K. Sharma; Megan Beck; Hadallia Bergeron; Mark C. Hersam

Paper Abstract

Molybdenum ditelluride (MoTe2), which can exist in a semiconducting prismatic hexagonal (2H) or a metallic distorted octahedral (1T') phases, is one of the very few materials that exhibit metal-semiconductor transition. Temperature-driven 2H – 1T’ phase transition in bulk MoTe2 occurs at high temperatures (above ~900 C) and it is usually accompanied by Te loss. The latter can exacerbate the control over reversibility of the phase transition. Here, we study effects of high-temperature annealing on phase transition in MoTe2 single crystals. First, MoTe2 were grown in sealed evacuated quartz ampoules from polycrystalline MoTe2 powder in an iodine-assisted chemical vapor transport process at 1000 C. The 2H and 1T’ phases were stabilized by controlling the cooling rate after the growth. In particular, slow cooling at 10 C/h rate yielded the 2H phase whereas the 1T’ phase was stabilized by ice-water quenching. Next, the phase conversion was achieved by annealing MoTe2 single crystals in vacuum-sealed ampoules at 1000 C with or without additional poly-MoTe2 powder followed by fast or slow cooling. Similarly to the CVT growth, slow cooling and quenching consistently produced 2H and 1T’ phases, respectively, regardless of the initial MoTe2 crystal structure. We will discuss structural and optical properties of the as-grown and phase-converted MoTe2 single crystals using TEM, SEM/EDS, XRD, XPS and Raman. Electrical characteristics of two-terminal devices made from metallic 1T’ and bottom-gated FETs made from 2H exfoliated crystals will also be presented.

Paper Details

Date Published: 11 November 2016
PDF: 1 pages
Proc. SPIE 9924, Low-Dimensional Materials and Devices 2016, 99240D (11 November 2016); doi: 10.1117/12.2241809
Show Author Affiliations
Albert V. Davydov, National Institute of Standards and Technology (United States)
Sergiy Krylyuk, National Institute of Standards and Technology (United States)
Irina Kalish, National Institute of Standards and Technology (United States)
Louisa Meshi, Ben-Gurion Univ. of the Negev (Israel)
Ryan Beams, National Institute of Standards and Technology (United States)
Berc Kalanyan, National Institute of Standards and Technology (United States)
Deepak K. Sharma, National Institute of Standards and Technology (United States)
Megan Beck, Northwestern Univ. (United States)
Hadallia Bergeron, Northwestern Univ. (United States)
Mark C. Hersam, Northwestern Univ. (United States)

Published in SPIE Proceedings Vol. 9924:
Low-Dimensional Materials and Devices 2016
Nobuhiko P. Kobayashi; A. Alec Talin; M. Saif Islam; Albert V. Davydov, Editor(s)

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