- 學位論文
施加電場退火對不同成分之鋯鈦酸鉛薄膜特性的影響
Effect of applying electric bias at different thermal stages on the properties of PZT thin films with distinct Zr/Ti ratios
摘要
Pb ZrxTi1-x O3 (PZT) thin films were deposited through chemical solution deposition (CSD) on Pt/ TiOx/ SiO2/ Si substrates. The deposited films with three distinct Zr/ Ti ratios were followed by annealing at 700℃for 30 min. During annealing, an in situ electric-bias was conducted by applying a ~333KV/cm electric field across the films at different thermal stages. It was found that the electric-bias-annealing had significant influences on the preferred orientations, microstructures, and ferroelectric properties of PZT films with different Zr/ Ti ratios. In Zr55, the crystal orientations changed with electric-bias conditions, which exhibited a random orientation when it was biased during holding, but slightly (101)/(110) preferred when biased during both holding and cooling, and the biased Zr55 during cooling showed the (001)/(100) preferred orientation. Additionally, the 2Pr values of Zr55 increased when it was either positively or negatively biased during both holding and cooling. On the other hand, the bias condition did an insignificant influence on the texture structure in Zr40 and Zr60. However, the positive biased Zr40 specimens exhibited increased 2Pr values, whereas the 2Pr values increased when Zr60 samples was applied by a negative bias. The fatigue property was better in the negative biased PZT films than that in the positive biased one. A possible mechanism of the negative-bias-assisted the positive carrier’s migration to leave the PZT/electrode interface to improve the fatigue property in PZT was proposed.
並列摘要
本實驗以溶膠凝膠法配置不同Zr/Ti比例之鋯鈦酸鉛(PZT)溶液，以旋鍍方式鍍於Pt/ TiOx/ SiO2/ Si基板，並在鐵電薄膜退火過程中階段性的施加垂直膜面的正負電場，探討在不同階段下施加電場對薄膜特性的影響。本實驗施加於試片之電場約為333KV/cm，遠大於文獻中所提及之電場強度及矯頑電場。 實驗結果顯示，隨著不同成分及不同的加電場條件，均會對其薄膜優選方向、顯微結構以及鐵電特性等有所影響。在Zr/Ti比例為Zr55時，隨著不同的電場條件其優選方向隨之改變；在Holding時施加電場，薄膜趨向random；在Holding and Cooling時加電場，則呈現些微(101)/(110)優選方向；而在Cooling時，優選方向則為(001)/(100)。此外，殘留極化值的表現上，在Holding and Cooling施加正負電場均有較好的表現。至於Zr40及Zr60方面，電場的施加對於其織構的影響不大；然而對Zr40的薄膜，施加正電場可使殘留極化值得到提升，反之，Zr60則是在負電場下有較高的極化值。 經疲勞測試可發現在不同成分下，施加負電場退火之試片其疲勞特性均優於正電場退火，推測在熱處理過程中施加負電場可使累積在底電極及薄膜介面之缺陷(如電動)產生移動，進而改善薄膜的疲勞特性。