Systematic investigation of the annealing temperature and composition effects on the dielectric properties of sol-gel Ba_xSr_(1-x)TiO_3 thin films

摘要

In this work, Ba_xSr_(1-x)TiO_3 sol-gel thin films (x=0.7, 0.5 and 0.3) deposited on Pt/Si substrate and post-annealed at different temperatures have been investigated. A systematic study of the structure, microstracture and dielectric properties has been achieved for each composi tion. To our knowledge, for the first time, a systematic effect of post-deposition annealing temperature and composition is reported. For each Ba/Sr ratio, higher annealing temperature leads to crystallinity improvement and to grain growth. A shift of the ferroelectric to paraelectric transition toward the bulk Curie temperature with the increase of the annealing temperature is shown. These results are correlated with the increase of the permittivity, tunability and dielectric losses measured on MIM capacitors at low frequency. Moreover, the high frequency results, between 800 MHz and 30 GHz, are in very good agreement with low frequency measurements, and show a huge tunability up to 80% under 600kV/cm.