Phase stability in MoTe₂ prepared by low temperature Mo tellurization using close space isothermal Te annealing

In this work, we used isothermal close space (ICS) Te annealings in pure H₂ atmosphere for the tellurization of Mo oxide thin films. Differently to previous open tube tellurization annealings, ICS is expected to provide a higher Te vapor pressure because the chamber containing the Te source and the substrate is very small and semi-closed. Then, we used a relatively low temperature of 500 °C at which, according to the phase diagram, 2H phase should be stable. However, we observed that, in all cases, Mo oxide initially transformed to 1T′ before reaching the equilibrium 2H phase. Highly oriented MoTe₂ films with the [001] direction perpendicular to the surface were obtained in all samples. On the other hand, according our X-ray photoelectron spectroscopy measurements, we report shifts of 0.38/0.27 eV in the 3d emission of Te/Mo between the two different phases which probably have a chemical origin.