Measurement of the permittivity and loss of high-loss materials using a Near-Field Scanning Microwave Microscope

Traceable measurement and imaging of the complex permittivity of a multiphase mineral specimen at micron scales using a microwave microscope

“…The NSMM is calibrated [11] from approach curve measurements on isotropic and reproducible materials for which traceable measurements of permittivity are available. High-purity polished fused silica (FSIL), undoped single-crystal yttrium aluminium garnet (YAG) and lanthanum aluminate (LAO) are used in the work described.…”

“…1. A detailed account of the design and construction of the microscope has recently been published [11]. In the present paper, calibration and imaging measurements are made with a spherical tip 0.1Ø mm manufactured by electro-discharge machining (EDM) [12], and a conical tip manufactured by electrochemical etching (Everbeing T20-100) -see Fig.…”

“…Accurate models that incorporate the tip geometry have been developed for use in Electrostatic Force Microscopy (EFM) experiments for measuring permittivity [14], but these are not directly applicable. It is well established [11] that cavity perturbation theory and an electrostatic model [2] (with modifications that will be summarised in Section III) can be used to obtain accurate measurements of permittivity and loss tangent using spherical tips. Measurements on polar liquids [11] have demonstrated that accurate measurement is possible even for high loss materials.…”

“…It is well established [11] that cavity perturbation theory and an electrostatic model [2] (with modifications that will be summarised in Section III) can be used to obtain accurate measurements of permittivity and loss tangent using spherical tips. Measurements on polar liquids [11] have demonstrated that accurate measurement is possible even for high loss materials. The electrostatic model is developed for an isolated sphere in proximity to a dielectric surface.…”

“…In the work presented the excitation voltage is ≤ 100 mV. Technical aspects of design of the NSMM are considered in greater detail in reference [11].…”