A study of charge-density-waves associated with the periodic lattice distortion in 1T-VSe ₂ using a low temperature scanning tunneling microscope

We have investigated the charge-density-wave (CDW) formation associated with the periodic lattice distortion in 1T-VSe ₂ by using a low temperature scanning tunneling microscope (STM) at 4.2 K. To clarify the atomic and the superlattice structures, we used a layer etching technique to fabricate a step of 1T-VSe ₂ with a height of ≈ 6 Å and investigated the atomic structures at 4.2 K on the newly etched region. The measured images showed a clear isotropic 4 × 4 charge-density-wave structure which was different from the previous results obtained by Coleman et al. The high resolution STM images at 4.2 K showed that the center of CDW was surrounded by three surface atoms from those images we were able to identify those atoms as Se. The surface Se atoms determined the STM pattern because of their proximity to the scanning tip.