This work reports experimental demonstrations of reversible crystalline phase transition in ultrathin molybdenum ditelluride (MoTe2) controlled by thermal and mechanical mechanisms on the van der Waals (vdW) nanoelectromechanical systems (NEMS) platform, with hexagonal boron nitride encapsulated MoTe2structure residing on top of graphene layer. Benefiting from very efficient electrothermal heating and straining effects in the suspended vdW heterostructures, MoTe2phase transition is triggered by rising temperature and strain level. Raman spectroscopy monitors the MoTe2crystalline phase signatures in situ and clearly records reversible phase transitions between hexagonal 2H (semiconducting) and monoclinic 1T′ (metallic) phases. Combined with Raman thermometry, precisely measured nanomechanical resonances of the vdW devices enable the determination and monitoring of the strain variations as temperature is being regulated by electrothermal control. These results not only deepen the understanding of MoTe2phase transition, but also demonstrate a novel platform for engineering MoTe2phase transition and multiphysical devices.
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.
more » « less- NSF-PAR ID:
- 10034462
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials
- Volume:
- 29
- Issue:
- 16
- ISSN:
- 0935-9648
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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