Antiferroelectricity in ZrO_2 and Ferroelectricity in Zr, Al, La Doped HfO_2 Nanoparticles

摘要

The dependence of the polarization P in Hf_(1-x)Zr_xO_2 nanoparticles on electric field, dopant concentration x, size and temperature are studied using the transverse Ising model and the Green's function method. Pure ZrO_2 shows at high electric fields an antiferroelectric behavior. Pure HfO_2 is a linear dielectric in the monoclinic phase. With increasing ZrO_2 content the of HZO shows a ferroelectric behavior. The composition dependence x of the remanent polarization P_r(x) has a maximum for x = 0.5. For x = 0, pure HfO_2, and x = 1, pure ZrO_2, P_r=0. P increases with decreasing HZO nanoparticle size. The influence of Al and La doping on P_r in HfO_2 nanoparticles is also studied. The exhibiting of the ferroelectricity in ion doped HfO_2 is due to a phase transformation and to an internal strain effect. The observed results are in good qualitative agreement with the experimental data.