Charge-density waves in Nb1 + xS2 crystals

In-situ intercalation of surplus niobium during heating of 3R-Nb_{1 + x}S₂ (x ≥ 0.09) layered crystals in ultra-high vacuum up to 1500 K triggered an unusual inter-polytypic transition from a trigonally prismatic coordinated polytype into an octahedrally coordinated one. The new polytype contains charge-density waves with a commensurate-incommensurate phase transition, temperature-dependent on the intercalated niobium concentration. Charge-density waves in the Nb_{1 + x}S₂ compound, observed for the first time here, were studied by transmission electron diffraction and scanning tunnelling microscopy.