Study On Lateral Size Effect Of PIN-PMN-PT Pyroelectric Thin Films

With the rapid development of pyroelectric infrared detection array technology,miniaturization,integration and high pixel count are gradually becoming the development trend of uncooled infrared detectors.Exploring and revealing the influence of the pyroelectric thin film array element size on its structure and pyroelectric performance is crucial for device design.In this thesis,a new generation of pyroelectric material Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃(PIN-PMN-PT)is used as the object of study to establish a simulation model to investigate the influence of the transverse dimensions of the film on its piezoelectric,dielectric and pyroelectric properties under different array shapes,orientations and phase structures by the method of finite element analysis.And the preparation of PIN-PMN-PT thin films and the micro-nano processing of thin film arrays were carried out experimentally,the main research contents and results are as follows.The theoretical model of the thin film array element for the piezoelectric,dielectric and pyroelectric properties of ternary relaxed ferroelectric materials PIN-PMN-PT and conventional pyroelectric materials was established by COMSOL simulation software,and the model was optimized in terms of mesh division,symmetry and boundary conditions.The results show that:(1)the piezoelectric coefficient and dielectric constant increase with decreasing the aspect ratio of the thin film arrays of different shapes,and the piezoelectric response is highest at the sidewalls of the arrays,and when the width to thickness ratio reaches a critical value After the width-to-thickness ratio reaches a critical value,the distribution of the highest piezoelectric response changes from the sidewall to the center,and the transverse size effect of the electrical properties of circular film arrays is more significant than that of rectangular arrays;(2)studies of different crystallographic orientations show that as the transverse size of the film decreases,the fastest increasing trend of d₃₃is for the[001]orientation,and the results of the transverse size effect of the dielectric constant are ?_?001?>?_?011?>?_?111?,and the dependence of[011]orientation on shape is stronger;in addition,the pyroelectric coefficient of the array element tends to decrease and then increase with decreasing aspect ratio in[001]and[111]orientations,and the turning point is at 3:1aspect ratio,while[011]shows the opposite situation;(3)the results of different phasestructures show that,in the R phase PIN-PMN-PT films exhibit a more pronounced transverse size effect.The analysis suggests that the aspect ratio of PIN-PMN-PT films changes significantly when the lateral size of the array element is reduced from 100?m to micron level,and that the array element is subjected to a change in strain grip between the substrate and the surrounding area,with corresponding changes in the internal phase structure and domain structure,thus affecting its macroscopic dielectric,piezoelectric and pyroelectric properties.To verify it experimentally,a patterned SrRuO₃conductive buffer layer was prepared on a single crystal substrate of SrTiO₃by pulsed laser deposition,and a PIN-PMN-PT pyroelectric film was further prepared with good ferroelectric and dielectric properties of the residual polarization intensity of 10.5?C/cm²and the coercive field of 7.7 kV/mm,and the electric domains shows a 180°flip with a significant micro-zone piezoelectric response.The lithography process of the array design has been improved,and a thin-film line array has been initially prepared,laying the foundation for further experimental verification.