STM studies of CDWs in pure and doped transition metal chalcogenides
- Univ. of Virginia, Richmond, VA (United States); and others
The effects of dilute impurity doping on charge-density wave (CDW) structures and gaps in NbSe{sub 3} 1T-TaS{sub 2} and 2H-NbSe{sub 2} have been studied by using a scanning tunneling microscope (STM) operating at 4.2 K. In Fe doped samples of NbSe{sub 3} the STM spectroscopy measurements indicate that the added impurities can significantly shift the CDW energy gaps. In NbSe{sub 3}, Fe reduces both CDW gaps by 25-30%, and produces changes in the conductance structure relative to the pure material. The images of Fe{sub 0.01}NbSe{sub 3} show that all three surface chains in the unit cell still carry a strong CDW modulation with no evident disorder. However, a change in the relative amplitudes of the high and low temperature CDWs is detected. The effects of Co and Ni impurities on the gaps in NbSe{sub 3} have also been studied. While Co increases both by 25-30%, Ni increases only the high temperature gap with the low temperature gap remaining essentially unchanged. In 1T-Fe{sub 0.05}Ta{sub 0.95}S{sub 3} the CDW energy gap is reduced by 50% and the resistive anomaly at the commensurate-incommensurate transition is moved. Disorder is evident in the CDW pattern, but the local CDW amplitude remains strong. In Fe doped 2H-NbSe{sub 2}, the 3 x 3 CDW pattern is still observed in local regions of the crystal. These studies indicate that the STM is a sensitive probe of effects of impurities on CDW structures and energy gaps.
- OSTI ID:
- 131202
- Report Number(s):
- CONF-920376-; ISSN 0003-0503; TRN: 95:007049-0027
- Journal Information:
- Bulletin of the American Physical Society, Vol. 37, Issue 9; Conference: Meeting of the American Physical Society, Indianapolis, IN (United States), 16-20 Mar 1992; Other Information: PBD: Dec 1992
- Country of Publication:
- United States
- Language:
- English
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