The doping of element (Nb, Ta, etc.) into MoS 2 , one of the layered transition metal dichalcogenides, is a key technology for electronic devices because the lack of the p-type MoS 2 has limited the range of applications. We report that the Mo 1-x Nb x S 2 thin films were synthesized on SiO 2 /Si substrates by chemical vapor deposition (CVD). It was critical to use chloride sources (MoCl 5 and NbCl 5) for the synthesis of Mo 1-x Nb x S 2. The Nb concentration can be increased to 10% by controlling the supplied amount of Nb using a separate-flow CVD apparatus. The Raman spectra changed as the Nb concentration increased, appearing E 2 (Nb-S) vibrational mode. The photoluminescence (PL) at 655 nm, 2 attributed to emission from excitons, disappeared, when Nb was incorporated into the MoS 2. PL due to trions at 680 nm was observed for the Mo 1-x Nb x S 2 thin films.