Infulence Of Ionizing Radiation On 180° Domain In Ferroelectric Thin Film

Ferroelectric memory is widely used in the field of aerospace because of low power consumption,high read and write speed and high integration.Capacitance,which is a basic storage cell of memory,is one of the main research objects when studying the performance of ferroelectric devices.Ferroelectric domain is a small area of spontaneous polarization with the same direction.The domain walls boundary between two domains is named as domain walls.The physical properties of the ferroelectrics are closely related to the structure and motion of ferroelectric domain and its domain walls.The main types of the ferroelectric with 180° domain walls are the domain walls of Ising,Bloch and Neel.The Bloch domain walls with bichiral can reduce the domain walls energy of the ferroelectrics,and has great potential in the research and application of high density storage devices.It is necessary to study the effects of radiation on ferroelectric devices under the trend of devices miniaturization and integrated circuit intensive.In this work,the Monte Carlo method and Landau-Ginzburg-Devonshire(LGD)theory are used to study the polarization distribution and ionizing radiation effects in ferroelectrics with 180° domain structure of Ising,Bloch and Neel domain walls.(1)The polarization distribution of Ising walls,Bloch walls and Neel walls in barium titanate film(BaTiO3)are simulated by LGD theory.The influence of temperature,gradient coefficient,electric field and stress on the polarization distribution are investigated.The simulation results show that the polarization and the width of the domain walls decrease with the increase of temperature.When the gradient coefficient increases,the magnitude of polarization decreases,while the width of the domain walls increases.Under the positive electric field,the polarization increases.When the tensile stress applied on the Ising domain walls,the polarization decreases.(2)The radiation effect of ferroelectric layer BaTiO3 in the structure of Pt/BaTiO3/Pt under the H+ ionizing radiation is studied by Monte Carlo method.The simulation results show that the stop position of H+ and the number of vacancies increase,when H+ energy increases from 10 keV to 100 keV.In addition,the stop position of H+ extend to the interior of the target and the number of vacancies reduces with the increase of angle from 0° to 90°.(3)The influence of oxygen vacancies induced by the radiation on polarization,potential,electric field and dielectric constant in Ising,Bloch and Neel domain walls are studied using LGD theory.When the oxygen vacancies density range increases form 1024 m-3 to 1027 m-3,the corresponding polarization and dielectric constant of the Ising domain walls are unchanged,while the potential and electric field decreases.Meanwhile,the corresponding polarization of the Bloch domain walls decreases,the potential and electric field increase,the dielectric constant is unchanged.