Scanning tunneling microscopy of 1T-TiSe2and 1T-TiS2at 77 and 4.2 K

Scanning tunneling microscopy (STM) studies of 1T-${\mathrm{TiSe}}_2$ and 1T-${\mathrm{TiS}}_2$ at 77 and 4.2 K show anomalously large modulations of 1 to 3 Å by the surface chalcogen atoms. The charge-density-wave (CDW) modulation in 1T-${\mathrm{TiSe}}_2$ which forms a 2${\mathrm{a}}_0$×${2\mathrm{a}}_0$×${2\mathrm{c}}_0$ superlattice between 202 K is also well resolved. The detailed superposition of the atomic and CDW modulations can be separated and both contribute equally to the STM response.