抄録
(Bax, Sr1-x)TiO3 (BST) films have been widely investigated because of expectations of their applications in microwave devices. In particular, there has been intense interest in new devices that use their nonlinear properties such as tunable devices and frequency mixers. In order to realize such devices, detailed evaluation of their nonlinear properties and numerical mode ling are important. In this paper, capacitance-voltage (C-V) characteristics of BST films prepared by sputtering were measured, and numerical fitting of a polynomial to the voltage-charge (V-Q) characteristics calculated from the C-V data was carried out. The results show that the measured data can be expressed with precision by a simple equation containing only linear and third order components, revealing that a practical experimental equation for the design of electrical circuits was obtained. Furthermore, a new equivalent circuit of the nonlinear dielectric film was proposed, and calculation of generation of third order frequency from a BST film capacitor was also performed. The measured third order component agreed exactly with the calculated results, revealing that our equivalent circuit is useful as an analysis method for circuits using nonlinear capacitors.
