  Great achievements have been made in alloying of two-dimensional (2D)
semiconducting transition metal dichalcogenides (TMDs), which can allow tunable
band gaps for practical applications in optoelectronic devices. However,
telluride-based TMDs alloys were less studied due to the difficulties of sample
synthesis. Here, in this work we report the large-area synthesis of 2D
MoTexSe2-x alloy films with controllable Te composition by a modified alkali
metal halides assisted chemical vapor deposition method. The as-prepared films
have millimeter-scale transverse size. Raman spectra experiments combining
calculated Raman spectra and vibrational images obtained by density functional
theory (DFT) confirmed the 2H-phase of the MoTexSe2-x alloys. The A1g mode of
MoSe2 shows a significant downshift accompanied by asymmetric broadening to
lower wavenumber with increasing value of x, while E12g mode seems unchanged,
which were well explained by a phonon confinement model. Our work provides a
simple method to synthesize large-scale 2H phase Te-based 2D TMDs alloys for
their further applications.
