Phase transition of Al₂O₃-encapsulated MoTe₂ via rapid thermal annealing

Among group VI transition metal dichalcogenides, MoTe₂ is predicted to have the smallest energy offset between semiconducting 2H and semimetallic 1T′ states. This makes it an attractive phase change material for both electronic and optoelectronic applications. Here, we report fast, nondestructive, and full phase change in Al₂O₃-encapsulated 2H-MoTe₂ thin films to 1T′-MoTe₂ using rapid thermal annealing at 900 °C. Phase change was confirmed using Raman spectroscopy after a short annealing duration of 10 s in both vacuum and nitrogen ambient. No thickness dependence of the transition temperatures was observed for flake thickness ranging from 1.5 to 8 nm. These results represent a major step forward in understanding the structural phase transition properties of MoTe₂ thin films using external heating and underline the importance of surface encapsulation for avoiding thin film degradation.