The spectroscopic resolution of tunneling measurements performed with a scanning tunneling microscope is ultimately limited by the temperature at which the experiment is performed. To take advantage of the potential high spectroscopic resolution associated with operating an STM in a dilution refrigerator we have designed a room temperature tunnel current amplifier having very small back-action on the tunnel contact and allowing to nearly reach the predicted energy resolution. This design is a modification of the standard op-amp based tip-biasing current-voltage converter which implements differential voltage sensing and whose back action on the tip voltage is only ~2 μV rms for a 14 MV/A transimpedance and 22 kHz bandwidth.
@article{arxiv.physics/0610280,
title = {Room-temperature tunnel current amplifier and experimental setup for high resolution electronic spectroscopy in millikelvin STM experiments},
author = {H. Le Sueur and P. Joyez},
journal= {arXiv preprint arXiv:physics/0610280},
year = {2007}
}
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Available at http://www-spht.cea.fr/articles/s06/033