Texture Control And Electrical Properties Of NKBT Lead-free Ferroelectric Thin Films

Nowadays, the ferroelectrics have been viewed as one of the key functionalmaterials. However, the widely used ferroelectric materials often contain higher leadcontent at present, which is a fatal threat to environment and human health.Therefore considerable attention is drawn to the development and research of lead-free ferroelectric materials. Due to the high Curie temperature at room temperatureand strong ferroelectricity, the sodium bismuth titanate （NBT） is considered as one ofthe promising lead-free ferroelectric materials. The research on functional materialshas dramatically turned bulk materials towards thin film as the rapid development ofmicroelectronics integrated technique. Currently, much attention is mainly focusedon bulk material for NBT, there is a limitation on its thin film as a result of manydeficiencies: a poor degree of texture, a higher crystallization temperature, a lowerremanent polarization, a higher leakage current density and the difficulty in reversalof polarization. In comparison with pure NBT, the NBT-based solid solution （NKBT）modified with potassium bismuth titanate （KBT） shows enhanced performances,which is becoming a hot topic.In this paper, the NKBT thin films were successfully prepared using sol-gel spinon technique, a series of studies have been carried on against with these deficienciesof NKBT film in order to optimize its properties. The influence of heat treatmenttemperature on crystallization behavior of NKBT thin film is investigated, the resultsshow that the crystallization degree of NKBT film becomes fully, additionally, thepreferred orientation and electric properties of (Pb_1-x-yLa_xCa_y)Ti_1-x/4O₃thin film withdifferent compositions are also discussed, it is found that the (Pb_1-x-yLa_xCa_y)Ti_1-x/4O₃films show the low temperature crystallization and strong texture characteristics;finally, the effects of PLCT seed layer on preffered orientation, surface morphologyand electric properties of NKBT thin films are studied in detail. The results show thatthe preferential orientation and electric properties of NKBT films can be greatlyenhanced by introducing PLCT seed layer, the NKBT film with14nm-thickness seed layer posesses optimal properties: a higher （100） orientation, a lower surfaceroughness, a larger remanent polarization, a lower dielectric loss.