Millimeter-Wave WGM Resonator-Based Characterization of Continuous and Noncontinuous Ultrathin Cu Films

• Published in: IEEE microwave and wireless components letters Vol. 29; no. 5; pp. 363 - 365
• Main Authors: Barannik, Alexander A., Cherpak, Nickolay T., Protsenko, Irina A., Vitusevich, Svetlana A.
• Format: Journal Article
• Language: English
• Published: IEEE 01-05-2019
• Subjects: <italic xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">Q -factor; Conductivity; Copper; Dielectrics; Indexes; Millimeter-wave devices; Q-factor; Resonant frequency; resonator; Software; thin films
• ISSN: 1531-1309; 1558-1764
• DOI: 10.1109/LMWC.2019.2902952

We analyze the experimental data on the evolution of the microwave (MW) response of the whispering gallery mode (WGM) resonator. The focus is on the thickness <inline-formula> <tex-math notation="LaTeX">d_{f} </tex-math></inline-formula> variation of the conducting endplates (CEPs) from <inline-formula> <tex-math notation="LaTeX">d_{f} </tex-math></inline-formula> exceeding skin layer thickness <inline-formula> <tex-math notation="LaTeX">\delta _{s} </tex-math></inline-formula> to <inline-formula> <tex-math notation="LaTeX">d_{f}\ll \delta _{s} </tex-math></inline-formula> down to <inline-formula> <tex-math notation="LaTeX">d_{f} = 0 </tex-math></inline-formula>, i.e., with no CEPs. The analysis was performed by comparing the numerical simulation results obtained using COMSOL software with the authors' experimental data on the response of the Ka -band sapphire WGM resonator. The nonmonotonic change in the WGM resonator response with decreasing thickness <inline-formula> <tex-math notation="LaTeX">d_{f} </tex-math></inline-formula> is explained using the metal-insulator percolation model proposed by Krupka et al. We use a different resonator (quasi-optical) technique and different mode polarization, namely, the HE<inline-formula> <tex-math notation="LaTeX">_{14~1~\delta } </tex-math></inline-formula> mode. The artificially introduced discontinuity of the ultrathin film, resulting in a sharp growth of the <inline-formula> <tex-math notation="LaTeX">{Q} </tex-math></inline-formula>-factor is analogous with the percolation material structure. The revealed effect may be useful for the development of MW devices with dynamically controlled properties of metamaterials.