Investigation On The Microstructure And Physical Properties Of PbZr_xTi_1-xO₃Multilayers

PbZrxTi1-xO3(PZT) films are ideal candidates for manufacturing photonicdevices with controllable characteristics parameters due to tunable index ofrefraction with composition, high transparency over the visible and infrared spectralrange, and large electro-optic coefficient. The Solution to the problem of the width ofoptical reflection-band with high reflectivity for PZT-based Bragg reflector is narrowand the correlation between electrical properties and microstructure of the PZTmultilayer have been investigated systematically. Some major results obtained weredescribed as following:Firstly, following the principle of control of a single variable, the effect ofaverage molecular weight and content of polymer on the crystallographic properties,microstructure and optical properties of the PZT multilayer have been studiedrespectively. The optimal molecular weight and concentration of polymer(polyvinylpyrrolidone, PVP) for the preparation of PZT-based Bragg reflector havebeen obtained by exploring the evolution of the physical characteristics of the PZTmultilayer with polymer molecular weight and concentration. It was proved that themultilayer derived from chemical solution containing PVP with molecular weight of58,000and relative molar amount of x=1.0exhibits the optimal performance withhighest optical refectivity of89%and largest stop-band width of44nm.Secondly, a technology of fabricating one-dimensional non-periodicall-dielectric mirror was developed based on ferroelectric and paraelectric materials.A one-dimensional non-periodic system was constructed through the introduction ofFibonacci sequence with inner mirror symmetry and paraelectric materials SrTiO3into PZT multilayer. The obtained irregular multilayer exhibits superior opticalperformance over the visible region, with a peak reflectivity of~95%and aband-width of~113nm. The width of optical reflection-band with high reflectivityfor the irregular multilayer is2-3times of the traditional periodic ferroelectricmultilayer.Thirdly, the effect of microstructure on the electrical properties of the PZTmultilayer have been studied by means of varying the average molecular weight andcontent of PVP added in precursor solutions. Dielectric dispersion curves of PZTmultilayer reveals that the large apparently relative dielectric constant of these multilayer at low-frequency limit is contributed mainly by the interfacial polarization.(P–E) characteristic curves display that the effect of the average molecular weightadded in precursor solutions on the remnant polarization of PZT multilayer isnegligible and increasing concentration of PVP can leads to the rise of remnantpolarization. It can be concluded that remnant polarization of PZT multilayer here ismainly correlated to the porosity within the materials.Finally, electrical properties of PZT-based optical micro-cavity derived fromone single chemical solution were studied. Making full use of the evolution ofcrystallization characteristics and microstructure of the PZT films with annealingtemperature, a Fabry-Perot optical micro-cavity has been fabricated by using onesingle precursor. It was found that the obtained PZT-based optical micro-cavity notonly displays clearly identifiable micro-cavity mode (quality factor of~44), goodcrystalline properties and film quality, even more importantly, the multilayer alsoexhibits a very excellent electrical properties. Compared with quasi-periodic PZTmultilayer prepared by the same chemical solution, the residual polarization (46.9μC/cm2), the low-frequency dielectric constant (~716at1KHz) and the dielectrictuning rate (~49%at1MHz) of PZT-based optical micro-cavity have increased by11%,17%and22%, respectively.