Charge-density waves on cleaved surfaces of 1T-${\mathrm{TaS}}_2$ appeared at 77 K as hexagonal arrays of mounds with spacings of (3.5±0.3)${\mathrm{a}}_0$, where ${\mathrm{a}}_0$=3.346 Å is the lattice spacing of the 1T-${\mathrm{TaS}}_2$. In contrast, cleaved surfaces of 2H-${\mathrm{TaSe}}_2$ at 77 K showed only atoms. The tunneling microscope was operated under liquid nitrogen with a ${\mathrm{Pt}}_{0.8}$${\mathrm{Ir}}_{0.2}$ tip for both types of samples.

• Received 4 June 1985

DOI:https://doi.org/10.1103/PhysRevLett.55.394