Abstract
A scanning tunneling microscope (STM) has been used to measure energy gaps in the charge-density-wave (CDW) phases of the layer-structure dichalcogenides and in the high-temperature superconductor . Measured values of at 4.2 K for 2H-, 2H-, and 2H- are 80, 50, and 34 meV giving values of 2/ equal to 15.2, 15.4, and 23.9, indicating strong coupling in these CDW systems. Measured values of at 4.2 K in 1T- and 1T- are ∼150 meV for both materials giving 2/≊5.8. STM scans of at 4.2 K resolve atoms on the layer and show possible variations in electronic structure. The energy gap determined from I versus V and dI/dV versus V curves is in the range 30–35 meV giving values of 2Δ/≊8. Spectroscopy measurements with the STM can exhibit large zero-bias anomalies which complicate the analysis of the energy-gap structure, but adequate separation has been accomplished.
- Received 27 June 1990
DOI:https://doi.org/10.1103/PhysRevB.42.8890
©1990 American Physical Society