Characterization Of Ferroelectric Polarization And Domain Structure Of Molecular Ferroelectrics Based On Confocal Micro-Raman Spectroscopy

Ferroelectric materials are widely applied in sensing,mechanical driving,energy and information technologies,due to their unique ferroelectric,pyroelectric,piezoelectric and dielectric properties.In 1920,ferroelectricity was firstly discovered on Rochelle salt crystal.After more than100 years of development,today,the ferroelectric family is thriving and the research on ferroelectric has been an important branch of condensed matter physics.Especially in recent years,the fast development of modern electronics is generating high demand for cost-effective,light weight,flexible and environmental-friendly functional materials,which make researchers in chemistry,physics and material sciences focus on the newly emerged molecular ferroelectric materials.The study of ferroelectric domains is of great interest due to their importance in both fundamental studies and application exploration.For example,various nonlinear optical and optoelectronic devices can hardly be produced without the creation of a tailored domain structure,and mechanical actuators or electronic memories can hardly be developed without the inversion of domains induced by a mechanical force or an electric field.To meet those research requirements,there are many methods to characterize ferroelectric domains,namely,scanning probe microscopy,optical microscopy,electron microscopy,etc.However,most of the conventional methods require either a complicated preparation process or direct contact between physical probes and material surfaces,which cannot realize the three-dimensional detection,limiting the development of molecular ferroelectric materials.In this thesis,we utilized the confocal micro-Raman spectroscopy,as a nondestructive and noncontact in-situ method to characterize the ferroelectric polarization and domain structures in molecular ferroelectrics.Taking the recently reported molecular ferroelectric trimethylchloromethyl ammonium trichlorocadmium（II）（TMCM-Cd Cl₃（II））as an example,the non-180°domains of films have been characterized and visualized at different temperatures.Such a method is simple and requires minimum sample preparation,which would further benefit the research of molecular ferroelectric domain engineering and promote the miniaturization and integration of molecular ferroelectric films.