Atomic and electronic structures of the two different layers in 4Hb-TaS2at 4.2 K

We have studied the atomic and electronic structures of the two different layers in 4Hb-${\mathrm{TaS}}_2$ prepared by a layer-by-layer etching technique using a scanning tunneling microscope at 4.2 K. One layer (1T) showed the typical $\sqrt{13}$×$\sqrt{13}$ charge-density-wave structure, whereas the other layer (1H) had at low bias a triangular atomic structure with weakly superposed 3×3 and at high positive bias a $\sqrt{13}$×$\sqrt{13}$ charge-density-wave structure originating from the lower 1T layer due to tunneling through the top 1H layer. The bias-dependent-intensity of this charge-density-wave structure was shown to be consistent with room-temperature measurements, showing that this is a real intrinsic property of the material. Measured tunneling spectra of each layer at 4.2 K showed a metallic 1H layer and an insulating 1T layer with an opening of wide-gap structures at the Fermi level.