晶界可調變電性之鈦酸鍶鈣材料研究

Abstract

鈦酸鍶鈣[(Sr0.9Ca0.1)TiO3/SCT]塊材與薄膜皆可利用二階段式燒結控制其晶粒成長，此外藉是否由晶界驅入Li-Mn，可以SCT製作出電阻、電容及變阻器等具不同特性的被動元件。其中比起傳統式燒結所得SCT塊材，經由二階段式燒結[T1=1350/0m、T2=1230/20h]所得SCT塊材，不但晶粒大小(＜10 μm)分佈均勻且密度更近似理論密度外，更是ρ<1 Ω˙cm之半導化基板，另外利用均溫處理將Li-Mn驅入SCT晶界後，可以製作出SCT塊材電容與變阻器等元件。SCT薄膜以旋鍍之方式鍍膜於經研磨、拋光後SCT塊材基板上，SCT薄膜表面微結構與燒結氣氛有很大的關係，其中在H2-N2的燒結氣氛下SCT薄膜表面並無明顯的晶界存在，而CO-CO2的燒結氣氛卻可使在SCT表面上的晶粒分佈均勻，相同的，二階段退火的熱處理則可SCT薄膜表面晶粒不再成長；利用調整激光雷射擇區驅入的條件，可以得到電阻在5~200 kΩ範圍之可調式SCT薄膜電阻、電容值在2~3 nF (介電損失約15~20 %) 之SCT薄膜電容、以及非線性係數在4~7 (崩潰電壓約為7~9 V)之SCT變阻器。

A two-step sintering process has been investigated in order to control the grain growth of strontium calcium titanate [(Sr0.9Ca0.1)TiO3/SCT]. Using furnance to drive Li-Mn into SCT grain boundary, various passive components including resistors, capacitors, and varistors can be obtained. For SCT bulk material, uniform grain size (＜10 μm), high density, and ρ<1 Ω•CM can be achieved after two-step sintering [T1=1350/0min、T2=1230/20h]. Furthermore, SCT capacitors and varistors can be fabricated after Li-Mn elements were driven into grain boundary. On the other hand, the SCT thin films were deposited on polished SCT bulk substrate by spin coating. It was observed that the microstructure of SCT thin films was dependent on the annealing atmosphere. Under H2-N2 atmosphere, the grain boundary can not be clearly discerned on SCT film surface. In contrast, the grain size was uniform under CO-CO2 atmosphere by two-step annealing process. The SCT films with the resistances of 5-200 kΩ, the capacitances of 2-3 nF (dielectric loss15-20 %), and the nonlinear coefficient of 4-7 (breakdown voltage 7-9 V) for varistors can be controlled by changing the laser driving conditions.