Monolayer molybdenum ditelluride (MoTe2) attracted intensive scientific interest due to the small energy difference between its semiconducting (1H) and semimetallic (1T’) phases. Understanding MoTe2 polymorphism phenomena and developing pathways to induce reversible phase transformations is of great scientific and practical importance to develop semiconductor– semimetal phase change devices. In this paper, we show how thermal annealing induces phase transition in both 1H and 1T’ phases of chemical vapor deposition (CVD) grown MoTe2. We also show that depending on the temperature, those transformations are reversible. The material is kept stable by encapsulating it with CVD-grown graphene and the thermal treatments are performed in ultra-high vacuum to prevent oxidation. MoTe2 is characterized in its different phases via Raman spectroscopy and transmission electron microscopy. We report a 1H to 1T’ transition temperature of ∼1090 ◦C and observe reversion (i.e. 1T’ to 1H transition) at ∼900 ◦C. Density functional theory simulations are performed to gain insight on the experimentally measured 1H-1T’ critical transition temperatures. These findings are relevant for fundamental understanding of phase transition phenomena in monolayer MoTe2 that find applications in memories, transistors and semimetal–semiconductor junctions.

Reversible semimetal–semiconductor phase transition in CVD-grown monolayer MoTe2

Khaustov, V O
;
Convertino, D;Martini, L;Coletti, C
2025

Abstract

Monolayer molybdenum ditelluride (MoTe2) attracted intensive scientific interest due to the small energy difference between its semiconducting (1H) and semimetallic (1T’) phases. Understanding MoTe2 polymorphism phenomena and developing pathways to induce reversible phase transformations is of great scientific and practical importance to develop semiconductor– semimetal phase change devices. In this paper, we show how thermal annealing induces phase transition in both 1H and 1T’ phases of chemical vapor deposition (CVD) grown MoTe2. We also show that depending on the temperature, those transformations are reversible. The material is kept stable by encapsulating it with CVD-grown graphene and the thermal treatments are performed in ultra-high vacuum to prevent oxidation. MoTe2 is characterized in its different phases via Raman spectroscopy and transmission electron microscopy. We report a 1H to 1T’ transition temperature of ∼1090 ◦C and observe reversion (i.e. 1T’ to 1H transition) at ∼900 ◦C. Density functional theory simulations are performed to gain insight on the experimentally measured 1H-1T’ critical transition temperatures. These findings are relevant for fundamental understanding of phase transition phenomena in monolayer MoTe2 that find applications in memories, transistors and semimetal–semiconductor junctions.
2025
Settore PHYS-03/A - Fisica sperimentale della materia e applicazioni
Settore ICHI-01/A - Chimica fisica applicata
Settore PHYS-04/A - Fisica teorica della materia, modelli, metodi matematici e applicazioni
Settore IMAT-01/A - Scienza e tecnologia dei materiali
CVD; phase transition; MoTe2; monolayer; annealing; Raman spectroscopy; quantum materials
   Graphene Flagship Core Project 3
   GrapheneCore3
   European Commission
   Horizon 2020 Framework Programme
   881603

   NATIONAL QUANTUM SCIENCE AND TECHNOLOGY INSTITUTE (NQSTI) Partenariato Esteso (PE0000023)
   NQSTI
   MUR
   PNRR
   PE00000023

   Deutsche Forschungsgemeinschaft
   DFG, German Research Foundation
   471707562

   Next Generation EU, mission4, component2
   European Union
   CUP E63C22000970007
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11384/152043
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