Surface modes in a ferroelectric film

Abstract

We discuss polarisation surface modes in the paraelectric phase of a cubic ferroelectric film by means of a phenomenological Landau theory. The film is extended to infinity in the two(x, y) lateral directions and is in contact with two semi-infinite isotropic dielectric media. Surface polarisation energy is taken into account in the expression of boundary conditions for polarisation modes which are treated in the electrostatic approximation. There are two types of propagative normal modes : surface modes with an exponential dependence of the amplitude on distance across the film and so called guided wave modes. We have determined the frequencies and the eignvectors of the modes.

Keywords:

• Dielectric polarisation
• phase transitions
• surface waves
• thin films