Tailoring the Phase in Nanoscale MoTe₂ Grown by Barrier-Assisted Chemical Vapor Deposition

Abstract

We employed chemical vapor deposition (CVD) from powder precursors aiming at large-area growth of molybdenum ditelluride (MoTe2) thin films, with controlled allotropic 2H and 1T′ phases. This major outcome entails tuning the parametric conditions of the precursor fluxes during the deposition. Using a physical barrier, we induce a concentration gradient of the Te precursor, thus enabling the control of the flux fluid dynamics and the formation of a Te-rich or Te-poor environment. As a consequence, the allotropic phase repartition in the films turns out to be determined by the barrier-induced Te concentration, as clearly evidenced by statistical Raman scattering investigations. The effect of the physical barrier is also reflected in the shape of the crystallite population and in their log-normal areal distribution pointing out to a homogeneous nucleation mode of the MoTe2 crystals. Our approach shows the selective allotropic phase control in the barrier-assisted CVD deposition of MoTe2 by adjusting the kinetics of the chemical reaction rather than with the use of growth surfactants.