Domain Motion Theory And Polarization Process Of Electro-Optical Characteristics Of BaTiO₃ Crystal Thin Film

Modern optical network signal processing requires high performance waveguide modulators,especially the ones based on the waveguide materials with the high electrooptical property.Barium titanate(BaTiO3)crystal thin film material has the advanced electrooptical property,high integrability and excellent substrate compatibility.At present,with the continuous development of microelectronic processing technology,BaTiO3 crystal thin film material has an important application prospect in high-speed electro-optical devices.Due to the current trend of device miniaturization,the mechanism of ferroelectric domain wall motion has the practical significance for the applications of material properties in the field of high-density memory technology.Starting with the molecular dynamic theory,this work investigates the theoretical model of the conservation the energy cost for the domain nucleation,the local kinetic and free potential energies in the formation of spontaneous polarization of BaTiO3 crystal thin film domain,and then creates the theoretical model for defining the dependences of the electrooptical characteristics on both the initial polarization and the temperature.Further,the systematic simulations for the temperature dependence of the polarization degradation of BaTiO3 crystal thin film show that,during the stabilization process,the equilibrium between the kinetics of domain motion and the free potential energy plays the key role in determining the polarization degree,while the polarization degree has dual nonlinear dependences on both the initial polarization and the temperature.Illustratively,when the initial polarization is 1.0,an expectable state,the polarization degree is almost independent of temperature,whereas when the initial polarization is 0.9,an increase of temperature from the room temperature to70°C can cause a degradation from 80% to 76.5%,while the continuous increase of temperature to 100°C can make the polarization degree come back to 80%.The c-axis orientation and the initial polarization of a BaTiO3 crystal film sample are measured,and a ridge waveguide electrooptic modulator is fabricated to measure the electrooptic coefficient r51 at several different temperatures.The results show a similar temperature dependence with the polarization degree.Illustratively,when the temperature increases from the room temperature to 70°C,r51 decreases from 806pm/V to 496pm/V,and then increases to669pm/V when the temperature increases to 85°C,proving the correlation between the polarization and the electrooptic properties.Hence,the achievements on electrooptic properties in this paper provide the important data for the application of BaTiO3 crystal thin films in more fields,showing an important academic value.