Characterization of Dielectric Properties of Conductive Materials by Coplanar Waveguide Method

A coplanar waveguide (CPW) method has been developed for characterization of conductive materials like carbon-content samples (graphite, pressed graphene, N-doped graphene) and anisotropic metasurfaces with planar metal inclusions. The samples have been placed as covers on the CPW conductor layout and additional losses and phase delay/advance have been used for simultaneous extraction of the equivalent conductivity and dielectric constant of these materials. Positive and negative values of the equivalent dielectric constant of the metasurfaces have been extracted in different directions and undue frequency dependence of the permittivity of pressed graphite and graphene samples between values 20–25 up to less than 1 above 30 GHz and equivalent conductivity about 0.3-8 S/m have been measured. A weak magneto-electric (ME) effect in external dc magnetic field has been observed for some carbon-content materials.