Comparison of scanning evanescent microwave microscopy with co-planar waveguide methods of characterization of Ba0.5Sr0.5TiO3 thin films

The permittivity of a barium strontium titanate thin film was measured at 1.8 GHz and 4.4 GHz with a scanning evanescent microwave microscope (SEMM) and co-planer waveguides (CPW). The raw data suggests the SEMM has sufficient sensitivity to detect significant variations in permittivity across the film that the CPWs could not. The average value of permittivity extracted from the data is consistent with that extracted from the co-planar waveguide measurements but the error bars associated with the extraction are large, of the order of 25 %. The significant contribution to the error in the final result from the SEMM is due to the analytical model used.