LOW-TEMPERATURE SCANNING-TUNNELING-MICROSCOPY SPECTROSCOPY STUDY OF 2DIFFERENT LAYERS IN POLY-TYPE 4HB-TAS2 AT 4.2 K

Using scanning tunneling microscope (STM), we have fabricated steps of 4Hb-TaS2 with the height similar to 6 Angstrom and investigated the e lectronic and atomic structures on the two different layers near the s tep region at 4.2 K. The measured STM images and tunneling spectra rev ealed completely different atomic and electronic structures of the 1T and 1H type layers. The 1T type layers showed the typical root 13 x ro ot 13 charge-density-wave (CDW) structures showing insulating behavior s, whereas the 1H type layers showed metallic behaviors and had the tr iangular atomic structure with a very weak 3x3 CDW superlattice at a l ow bias voltage and with a superposed root 13 x root 13 CDW superlatti ce at a high positive bias voltage. The bias dependent STM image on th e surface of 1H layer can be explained by the energy dependent tunneli ng process between STM tip and a stack of metallic 1H layer and insula ting 1T layer.