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  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.
Bibliographical noteFunding Information:
The authors acknowledge the CAPES (CAPES-INL 04/14, CAPES-PVE 88881.068066/2014-01), CNPq and FAPEMIG funding agencies for the financial support. Technical support of the Laboratory of Crystallography and the Center of Microscopy of the Universidade Federal of Minas Gerais is also acknowledged. Authors are indebted with S. de Roux and E. Romero Ibarra for assistance.
© 2017 Elsevier B.V.
- 2D materials
- Phase stability
- Transition metals dichalcogenides