Microwave Imaging
Scanning microwave impedance microscopy (MIM) is capable of mapping out the local dielectric and conductivity information of materials by guiding microwave signals (~1GHz) to a micro-machined cantilever. The spatial resolution is set by the tip size (~100nm) rather than the wavelength of the radiation. The microwave electronics can detect small capacitance changes below 1aF.
The room-temperature MIM is fully integrated with state-of-the-art atomic-force microscopy (AFM) platforms. We have so far obtained interesting images on semiconductor devices, chemically exfoliated graphene sheets, ferroelectric nano-particles, phase-change nano-wires, topological insulator nano-platelets, and biological samples. The instrument is now implemented as a general-purpose imaging tool for material science research.
Imaging at microwave frequencies is ideal to study local electrical information in complex materials and to reveal electronic inhomogeneity in multi-phase boundaries. Using a cryogenic MIM setup equipped with a 9T superconducting magnet, we have successfully imaged the colossal magnetoresistance effect in a manganite thin film. The system enables us to take a unique approach to many long-standing problems of condensed matter physics.
K. Lai, H. Peng, W. Kundhikanjana, D. T. Schoen, C. Xie, S. Meister, Y. Cui, M. A. Kelly, and Z.-X. Shen
Nanoscale Electronic Inhomogeneity in In2Se3 Nanoribbons Revealed by Microwave Impedance Microscopy
Nano Lett. 9, 1265 (2009)
W. Kundhikanjana, K. Lai, H. Wang, H. Dai, M. A. Kelly, and Z.-X. Shen
Hierarchy of Electronic Properties of Chemically Derived and Pristine Graphene Probed by Microwave Imaging
Nano Lett. 9, 3762 (2009)
