Dual modulation STM: Simultaneous high-resolution mapping of the differential conductivity and local tunnel barrier height demonstrated on Au(111)
- 8 June 2021
- journal article
- research article
- Published by AIP Publishing in Journal of Applied Physics
- Vol. 129 (22), 225301
- https://doi.org/10.1063/5.0051403
Abstract
We present a scanning tunneling microscopy (STM) technique to simultaneously measure the topography, the local tunnel barrier height (d /d ), and the differential conductivity (d /d ). We modulate the voltage and tip piezo with small sinusoidal signals that exceed the cut-off frequency of the STM electronics and feed the tunneling current into two lock-in amplifiers (LIAs). We derive and follow a set of criteria for the modulation frequencies to avoid any interference between the LIA measurements. To validate the technique, we measure Friedel oscillations and the subtle tunnel barrier difference between the and stacked regions of the Au(111) herringbone reconstruction. Finally, we show that our method is also applicable to open feedback loop measurements by performing grid ( ) spectroscopy.
Keywords
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