Nonlinear Reconstruction of Multilayer Media in Scanning Microwave Microscopy

Scanning microwave microscopy (SMM) is a nanoscale characterization technique widely used to image electrical or magnetic properties of materials at microwave frequencies. Nevertheless, it is challenging to reconstruct the properties of materials from measured SMM signals, and it is even difficult to retrieve multilayer media directly from measured signals. This paper proposes a nonlinear inversion scheme to quantitatively reconstruct multilayer media. In the forward solver, hybrid boundary integral-finite element method is used to reduce the computational cost. In the inverse problems, capacitance or conductance derivative signals at different probe-sample distances are used to retrieve multilayer media. Reconstructed results show that the proposed approach is able to reconstruct both permittivity and conductivity distributions under noisy environment in 3-D samples. Most importantly, it is found that the resolution has been significantly improved in the retrieved images compared with capacitance or conductance signals. To the best of our knowledge, it is the first time that the multilayer media in 3-D media is reconstructed in SMM.