Impacts of Radius on the Characteristics of Cylindrical Ferroelectric Capacitors

As a typical cell structure, the cylindrical ferroelectric capacitor (CFE-cap) has been widely used in 3-D ferroelectric memories. Unlike planar ferroelectric capacitor, the CFE-cap has nonuniform electric field and polarization distribution. In this article, we investigate the impacts of the radius on the capacitance, field distribution, electrode charge densities of both the isotropic and anisotropic CFE-caps. As the inner radius increases, the CFE-cap behaves more like the planar capacitor with the same ferroelectric thickness. The results indicate that CFE-cap has an additional knob of inner radius R-in to tune its ferroelectric and electric characteristics. We have considered two kinds of CFE-caps, isotropic and anisotropic CFE-caps. The former is found to have stronger ferroelectric response than the latter, such as higher normalized capacitance and larger polarization.