Ordered growth of hexagonal and monoclinic phases of MoTe2 on a sapphire substrate

Abstract

The transition metal dichalcogenides have been studied for various applications in electronics, sensing, or spintronics. Molybdenum ditelluride, MoTe₂, occurs in 3 crystal systems: hexagonal (2H), monoclinic (1T′), and orthorhombic (Td). Here we report on tellurisation of Mo and MoO₃ thin films to 2H-MoTe₂ and 1T′-MoTe₂ thin layers on sapphire substrates, respectively. To study the phases, we employed diffraction patterns using grazing-incidence wide-angle X-ray scattering, conventional X-ray diffraction and transmission electron microscopy (TEM). Measurements of pole figures confirmed the presence of a biaxial texture of both 1T′ and 2H phases. In the hexagonal phase, we found two ensembles of biaxially oriented crystallites offset by 30 degrees between the two groups. On the other hand, in the monoclinic layer, the crystallites follow the six-fold symmetry of the (0001) sapphire surface.