Synthesis of metallic mixed 3R and 2H NbS nanoflakes by chemical vapor deposition

In this work, we report the synthesis and characterization of mixed phase Nb 1+ x S 2 nanoflakes prepared by chemical vapor deposition. The as-grown samples show a high density of flakes (thickness ∼50 nm) that form a continuous film. Raman and X-ray diffraction data show that the samples consist of both 2H and 3R phases, with the 2H phase containing a high concentration of Nb interstitials. These Nb interstitials sit in between the NbS 2 layers to form Nb 1+ x S 2 . Cross-sectional Energy Dispersive Spectroscopy analysis with transmission electron microscopy suggests that the 2H Nb 1+ x S 2 region is found in thinner flakes, while 3R NbS 2 is observed in thicker regions of the films. The evolution of the phase from 2H Nb 1+ x S 2 to 3R NbS 2 may be attributed to the change of the growth environment from Nb-rich at the start of the growth to sulfur-rich at the latter stage. It was also found that the incorporation of Nb interstitials is highly dependent on the temperature of the NbCl 5 precursor and the position of the substrate in the furnace. Samples grown at high NbCl 5 temperature and with substrate located closer to the NbCl 5 source show higher incorporation of Nb interstitials. Electrical measurements show linear I - V characteristics, indicating the metallic nature of the Nb 1+ x S 2 film with relatively low resistivity of 4.1 × 10 −3 Ω cm. Systematic study of the effect of chemical vapor deposition conditions on the incorporation of Nb interstitials between NbS 2 layers.