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Microwave Frequency Comb from a Semiconductor in a Scanning Tunneling Microscope

Published online by Cambridge University Press:  20 December 2016

Mark J. Hagmann ,
Dmitry A. Yarotski  and
Marwan S. Mousa
Mark J. Hagmann*
Affiliation:
Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112, USA NewPath Research LLC, Salt Lake City, UT 84115, USA
Dmitry A. Yarotski
Affiliation:
Los Alamos National Laboratory, Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos, NM 87545, USA
Marwan S. Mousa
Affiliation:
Department of Physics, Mu’tah University, Al-Karak 61710, Jordan
*
*Corresponding author.mhagmann@newpathresearch.com
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Abstract

Quasi-periodic excitation of the tunneling junction in a scanning tunneling microscope, by a mode-locked ultrafast laser, superimposes a regular sequence of 15 fs pulses on the DC tunneling current. In the frequency domain, this is a frequency comb with harmonics at integer multiples of the laser pulse repetition frequency. With a gold sample the 200th harmonic at 14.85 GHz has a signal-to-noise ratio of 25 dB, and the power at each harmonic varies inversely with the square of the frequency. Now we report the first measurements with a semiconductor where the laser photon energy must be less than the bandgap energy of the semiconductor; the microwave frequency comb must be measured within 200 μm of the tunneling junction; and the microwave power is 25 dB below that with a metal sample and falls off more rapidly at the higher harmonics. Our results suggest that the measured attenuation of the microwave harmonics is sensitive to the semiconductor spreading resistance within 1 nm of the tunneling junction. This approach may enable sub-nanometer carrier profiling of semiconductors without requiring the diamond nanoprobes in scanning spreading resistance microscopy.

Keywords

scanning tunneling microscopyscanning probe microscopymicrowave frequency combspreading resistancelaser-assisted tunneling
Type
Related Techniques
Information
Microscopy and Microanalysis , Volume 23 , Special Issue 2: Atom Probe Tomography & Microscopy 2016 , April 2017 , pp. 443 - 448
Copyright
© Microscopy Society of America 2016 

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