Preparation And Doping Modification Of Barium Ditinatate Thin Films

As the increasing demand of ferroelectric devices in microelectronic and optoelectronic fields dramatically,there is a growing interest in ferroelectric thin films,especially novel lead-free thin films. Ba Ti2O5,as a new lead-free material,has a outstanding combination property,a high Curie temperature,good dielectric constant along the b-axis and low dielectric loss.Compared to the preparation of Ba Ti2O5 monocrystal and high b-axis orientation ceramics,the synthesis of b-axis orientation or doped thin films has an advantage in preparation cost and process conditions,and thin film also has significant potential application in the future.In the present study,the Ba Ti2O5 ferroelectric thin films were prepared by a sol-gel method,explored the relationship between the oriented growth and concentration of precursor solution, pyrolysis temperature and film thickness. Thin films were prepared on Pt(111)/Ti/Si O2/Si,Nb:Sr Ti O3(100) and Mg O(100) substrates,the surface topography and electrical properties of the prepared films were investigated. The remnant polarization of Ba Ti2O5 is too small,the preparation and investigation of element-doped Ba Ti2O5 thin films is necessary. Ba1-x Cax Ti2O5,Ba1-xSrx Ti2O5 and Ba Fex Ti2-x O5 thin films were prepared on Pt(111)/Ti/Si O2/Si substrates,the effect of doping elements and content on microstructure, dielectric and ferroelectric properties of Ba Ti2O5 thin films were investigated.The main results and conclusions are as follows:1. Stable precursor solutions were prepared by sol-gel,obtained the proper process conditions of heat treatment for the doped precursor solutions and thin films. Ba Ti2O5 thin films were prepared on Pt(111)/Ti/Si O2/Si,Nb:Sr Ti O3(100) and Mg O(100) substrates,the thin film on the Mg O(100) had a more denser surface.The remnant polarization(2Pr) and coercive field(2Ec) were higher with the applied field increasing,and the thin films on Pt(111)/Ti/Si O2/Si and Nb:Sr Ti O3(100) substrates had the maximum 2Pr of 0.61 ?C/cm2 and 1.41 ?C/cm2 under applied electric field(E) of 250 k V/cm respectively,and the later one had a higher dielectric constant.2. The Ba1-x Cax Ti2O5(x=0,0.01,0.02,0.03,0.04) thin films were prepared on Pt(111)/Ti/Si O2/Si substrates by the sol-gel method.The values of remnant polarization(2Pr) and coercive field(2Ec) increase as the Ca content increases. The thin film Ba0.97Ca0.03Ti2O5 had the maximum 2Pr of 1.36 ?C/cm2,and the maximum dielectric constant of 210(1 MHz). The Ba1-xSrx Ti2O5(x=0, 0.005, 0.01, 0.02, 0.05) thin films were also prepared under the same process conditions, The Ba1-xSrx Ti2O5 with x=0.02 had the maximum 2Pr of 1.00 ?C/cm2,had the maximum dielectric constant of 78(1 MHz).3. The Ba Fex Ti2-x O5 thin films were prepared based on the previous work,when the doped content of Fe was 0.8mol%,the thin film had better piezoelectric property,and had the maximum 2Pr of 1.68 ?C/cm2, the maximum dielectric constant of 175(1 MHz) respectively.