Wide frequency range ac electrical characterization of thick-film microvaristors

ZnO-based thick-film microvaristors were investigated using impedance spectroscopy. Properties of planar and sandwich structures on alumina and LTCC substrates with different electrode material are compared. Experimental characteristics are approximated with electrical equivalent circuit. Fabrication technology influence on proposed model parameters is presented. Temperature dependent behavior is shown. Schottky barrier height was calculated as 0.46 eV and three electrop trap levels with activation energy of 0.17 eV, 0.25 eV and 0.38 eV were found.