A Mach-Zehnder interferometer based tuning fork microwave impedance microscope*

The scanning microwave impedance microscope (MIM) makes available a non-contact means of determining the electrical properties of structures with high resolution [1, 2]. Commercial MIMs are used to detect defects in devices not easily seen by other means [3]. MIM is also a powerful probe for fundamental studies of new phenomena [4, 5]. Here we report a MIM setup based on a Mach-Zehnder interferometer through a home-built probe/tuning fork/PCB board configuration [6]. The setup is sensitive to small conductivity variations in the sample through the admittance modulation between the probe tip and the sample. The setup takes advantages of the large dynamic range of scattering matrix parameters of the microwave resonance, impedance matching condition for better tunability with broadband microwave frequency. Features of buried conducting and insulating structures can be measured. We discuss our setup as well as the sources and reduction of the noise.

[1] Y.-T. Cui et al., Rev. Sci. Instr. 87, 063711 (2016)
[2] S.-S. Tuca, et al., IEEE Trans. Nanotech. 16, 991(2017)
[3] H. P. Huber et al., Rev. Sci. Instr. 81, 113701 (2010)
[4] K. Lai et al., Phys. Rev. Lett. 107, 76809 (2011)
[5] M. Allen et al., PNAS 116, 14511 (2019)
[6] Z. Liu et al.,arXiv:2007.05888 (2020)