The layer stacking order in 2D materials strongly affects functional properties and holds promise for next-generation electronic devices. In bulk, octahedral MoTe2possesses two stacking arrangements, the ferroelectric Weyl semimetal Tdphase and the higher-order topological insulator 1T′ phase. However, in thin flakes of MoTe2, it is unclear if the layer stacking follows the Td, 1T′, or an alternative stacking sequence. Here, we use atomic-resolution scanning transmission electron microscopy to directly visualize the MoTe2layer stacking. In thin flakes, we observe highly disordered stacking, with nanoscale 1T′ and Tddomains, as well as alternative stacking arrangements not found in the bulk. We attribute these findings to intrinsic confinement effects on the MoTe2stacking-dependent free energy. Our results are important for the understanding of exotic physics displayed in MoTe2flakes. More broadly, this work suggests
Dynamic adhesion of 2D materials to mixed-phase BiFeO 3 structural phase transitions
Two-dimensional materials, such as transition metal dichalcogenides, have generated much interest due to their strain-sensitive electronic, optical, magnetic, superconducting, or topological properties. Harnessing control over their strain state may enable new technologies that operate by controlling these materials’ properties in devices such as straintronic transistors. Piezoelectric oxides have been proposed as one method to control such strain states on the device scale. However, there are few studies of how conformal 2D materials remain on oxide materials with respect to dynamic applications of the strain. Non-conformality may lead to non-optimal strain transfer. In this work, we explore this aspect of oxide-2D adhesion in the nanoscale switching of the substrate structural phase in thin 1T′-MoTe 2 attached to a mixed-phase thin-film BiFeO 3 (BFO), a multiferroic oxide with an electric-field induced structural phase transition that can generate mechanical strains of up to 2%. We observe that flake thickness impacts the conformality of 1T′-MoTe 2 to structural changes in BFO, but below four layers, 1T′-MoTe 2 fully conforms to the nanoscale BFO structural changes. The conformality of few-layer 1T′-MoTe 2 suggests that BFO is an excellent candidate for deterministic, nanoscale strain control for 2D materials.
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- NSF-PAR ID:
- 10352583
- Date Published:
- Journal Name:
- Journal of Applied Physics
- Volume:
- 132
- Issue:
- 4
- ISSN:
- 0021-8979
- Page Range / eLocation ID:
- 045301
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The fabrication of in‐plane 2H‐1T′ MoTe2homojunctions by the flux‐controlled, phase‐engineering of few‐layer MoTe2from Mo nanoislands is reported. The phase of few‐layer MoTe2is controlled by simply changing Te atomic flux controlled by the temperature of the reaction vessel. Few‐layer 2H MoTe2is formed with high Te flux, while few‐layer 1T′ MoTe2is obtained with low Te flux. With medium flux, few‐layer in‐plane 2H‐1T′ MoTe2homojunctions are synthesized. As‐synthesized MoTe2is characterized by Raman spectroscopy and X‐ray photoelectron spectroscopy. Kelvin probe force microscopy and Raman mapping confirm that in‐plane 2H‐1T′ MoTe2homojunctions have abrupt interfaces between 2H and 1T′ MoTe2domains, possessing a potential difference of about 100 mV. It is further shown that this method can be extended to create patterned metal–semiconductor junctions in MoTe2in a two‐step lithographic synthesis. The flux‐controlled phase engineering method could be utilized for the large‐scale controlled fabrication of 2D metal–semiconductor junctions for next‐generation electronic and optoelectronic devices.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1063/5.0096686
