Molecular dynamics simulations on ferroelectricity of AlN thin films

The recent realization of ferroelectricity in scandium- and boron-substituted AlN thin films has spurred tremendous research interests. Here we established a molecular dynamics simulation framework to model the ferroelectricity of AlN thin films. Through reparameterization of Vashishta potential for AlN, the coercive field strength and the AlN polarization were found to be close to experimental values. Furthermore, we examined the effects of film thickness, temperature, in-plane strain on polarization-electric field hysteresis loop, and the thickness-dependent Curie temperature. Lastly, we incorporated electrodes towards atomic-level modeling of ferroelectric device, by considering the induced charge at the interface between electrodes and ferroelectric film. We found that low dielectric contrast significantly lowers the coercive field for switching AlN.