The impedance of chemical vapor deposited CrO 2 and Cr 2O 3 bilayered thin films, composed of polycrystalline and amorphous structure, have been systematically studied in function of frequency and temperature. In the polycrystalline-CrO 2/amorphous-Cr 2O 3 bilayer, the real part of impedance at low frequency (f<300kHz) demonstrates a sharp transition at temperature around 330 K, with a specific feature of positive temperature coefficient, similar to the variation of dc resistance occurs at ferroelectric-paraelectric transition in the BaTiO 3 ceramics. In contrast, the imaginary part of impedance, at frequency f>300kHz, shows a characteristic of negative temperature coefficient. Further analysis of the frequency dependence of the impedance shows the contribution from the dynamics of both the dielectric and magnetic dipoles in the layers. Comparison of polycrystalline-CrO 2 and amorphous-Cr 2O 3 single layer with the CrO 2/Cr 2O 3 bilayer is discussed.
ASJC Scopus subject areas
- 物理與天文學 (全部)