Synthesis of Mo1−xNbxS2 thin films by separate-flow chemical vapor deposition with chloride sources

The doping of element (Nb, Ta, etc.) into MoS2, one of the layered transition metal dichalcogenides, is a key technology for electronic devices because the lack of the p-type MoS2 has limited the range of applications. We report that the Mo1−xNbxS2 thin films were synthesized on SiO2/Si substrates by chemical vapor deposition (CVD). It was critical to use chloride sources (MoCl5 and NbCl5) for the synthesis of Mo1−xNbxS2. 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 E2(NbS) vibrational mode. The photoluminescence (PL) at 655 nm, attributed to emission from excitons, disappeared, when Nb was incorporated into the MoS2. PL due to trions at 680 nm was observed for the Mo1−xNbxS2 thin films.