Preparation And Characterization Of Self-organized Nanostructures On The Surface Of Lithium Niobate Crystals

In recent years,lithium niobate crystals have been rapidly developed and widely used due to the excellent physicochemical properties,which are closely related to the domain structure.Therefore,The processing and preparation of the domain structure is critical for the application of the crystal.Low energy ion beam etching technology has the characteristics of low damage,controllable parameters and easy automation.It is more suitable for the preparation of nanostructures.In this paper,low energy ion beam etching technique is applied to prepare self-organized nanostructures,which mainly solves the three key problems of the preparation of nanostructures and domain structures and the change of ferroelectric properties.1)The variation of nanostructures with different incident angles,ion energy,etching time and ion types are researched.When the ion energy is 500e V and the beam current is 230?A/cm~2,the angle increases,and the surface forms point-cone and ripple nanostructure,and the roughness first increases and then decreases.When the ion energy is 700e V and the beam current is 354?A/cm~2,the angle increases,the surface forms ripple nanostructure,and the vertical height,roughness and structure order increase.When the ion energy is 500e V and the beam current is 230?A/cm~2,the etching time increases,the point cone transforms into the ordered ripple structure,and the height of the structure increases.When the incident angle is 60°and the beam current is 354?A/cm~2,the etching time is 60min,the structure height is low and the spectrum is fuzzy,and the order is poor;when etching for 120min,the spectrum is clear and the structure height increases.When the incident angle is 60°and the beam current is 230?A/cm~2,the ion energy increases,the smooth surface changes to the point-cone structure,the characteristic peak becomes higher,and the order increases.At 700e V,the point-cone structure is extremely high and orderly get worse.As the ion energy increases,the roughness and order increase first and then decrease.When the incident angle is 60°and the beam current is 354?A/cm~2,the ion energy increases,the smooth surface transforms into ripple structure,the height of the structure increases,the characteristic spectrum is clear,and the order is enhanced.The structure height and lateral dimension increase with the increase of ion energy.At the incident angle of 60°and the beam current of 230?A/cm~2,the Ar ion beam crystals form a smooth surface at low ion energy.Under the same parameters,the Xe ion beam induces the formation of point cone and ripple structures.Based on the single-factor experiment,the four-factor three-level orthogonal experiment of incident angle,ion energy,beam density and action time is studied to reflect the nanostructure under different parameters.The best experimental parameters of ion beam-induced crystals are obtained:incident angle 60°,beam current 265?A/cm~2,ion energy700e V,action time 90min.2)The shape and characteristics of the domain structure under different ion parameters are researched.The results show that three typical domain structures are formed on the crystal surface:dot domain,line domain and dendrite domain.The dendritic band shape of the dendritic domain deepens with increasing incidence angle.PFM results show that the crystal is in-plane polarized and the phase difference between positive and negative domains is 180°.The phase difference between the vertical and horizontal domains remains constant under the same parameter.As the ion energy increases,the phase difference becomes larger,and the bright and dark phases are obvious.The etching time increases,the phase difference decreases and the domain structure becomes denser.3)The changes of crystal structure and ferroelectric properties under different parameters are researched.XRD results indicate that ion beam etching only acts on the surface.The test results of ferroelectric properties under different ion parameters show that the spontaneous polarization intensity increases,the coercive field decreases and the residual polarization intensity increases before and after etching.