Summary form only given. We are developing a scanning tunneling microscope that is portable and optimized for scanning frequency comb microscopy (SFCM) as one part of our effort to complete a prototype for the carrier profiling of semiconductors by SFCM. Conventional integral or integral plus proportion feedback control of the tunneling current in a scanning tunneling microscope (STM) is satisfactory once tunneling has been established but may cause tip-crash by integral windup during coarse approach. In tip-sample contact images with atomic-resolution may be obtained but the microwave frequency comb ceases because there is no optical rectification and scanning tunneling spectroscopy also fails. We are studying a new control algorithm based on approximating the tunneling current as a polynomial in the bias voltage where the coefficients in this polynomial are not required. It is noted that hanges in the apparatus, as well as the algorithms used for feedback control in the STM, are required to optimize this instrument for measuring the microwave frequency comb.
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scanning frequency comb microscopy: a new method in scanning probe microscopy
Finer resolution with greater stability is possible using unique low-power (aW), low-noise (20 dB S/N), microwave harmonics generated within a nanoscale tip-sample junction for feedback control in place of the DC tunneling current. Please see the attached poster to be presented at the Microscopy & Microanalysis-2018 meeting in Baltimore Monday August 6th as Post-deadline poster PDP-18. Applications include true sub-nm resolution in the carrier profiling of semiconductors. This method is especially appropriate for resistive samples where the spreading resistance flattens plots of the tunneling current vs. tip-sample distance with a scanning tunneling microscope.
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- Award ID(s):
- 1648811
- NSF-PAR ID:
- 10066863
- Date Published:
- Journal Name:
- scanning frequency comb microscopy: a new method in scanning probe microscopy
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.13140/RG.2.2.34585.72804
