Phase control of sputter-grown large-area MoTe2 films by preferential sublimation of Te: amorphous, 1T′ and 2H phases

Abstract

Sputter-grown amorphous Mo–Te films were annealed to obtain the crystalline phase. Although as-deposited films exhibited an off-stoichiometric Te-rich composition, optimized annealing conditions enabled the elimination of excess Te by a preferential sublimation process. Owing to their similar local structure, the disordered amorphous phase first crystallized into a high temperature phase, 1T′, followed by a phase transition to the 2H structure upon further annealing. To realize 2D MoTe₂-based novel devices, understanding the crystallization mechanism of amorphous Mo–Te films is critical. Furthermore, the robustness of the fabrication method, i.e., the establishment of a method to realize MoTe₂ single-phase formation, which does not require the initial composition of the as-deposited amorphous film to be exactly stoichiometric, will greatly contribute to the deposition of large-area MoTe₂ films essential for industrial applications.