添加物對鈦酸鍶鋇薄膜顯微結構及其電性之影響

Abstract

本研究利用金屬有機分解法（MOD）在Pt/Ti/SiO2/Si基板上製備(Ba0.7Sr0.3)TiO3薄膜，添加各種添加物，如鑭、鈮、鎂，以及各種共添加物，如鎂-鑭、鎂-鈮，以XRD、SEM、TEM研究添加物對薄膜顯微結構的影響；以介電常數、漏電流的量測研究添加物對薄膜電性的影響。 在研究薄膜的成相過程中，發現在600℃~650℃的退火溫度下有一中間相的存在，利用XRD、TEM、FT-IR以及Raman對此中間相做一較深入的分析。結果顯示，此中間相為化學計量比 Ba2Ti2O5CO3 的中間碳酸物，其存在的溫度會隨著添加物的加入而提高。 在電性方面的研究：單一添加物（鑭、鈮、鎂）的添加都會使介電常數隨著添加量的增加而減少，並使的漏電流隨添加量的增加而下降。而在共添加系列（鎂-鑭、鎂-鈮）中，介電常數同樣隨著添加量的增加而減少，漏電流則隨著添加量的增加而下降，在鎂＝5 mol%，鑭（或鈮）＝10 mol%時，漏電流降到最低點，添加量再增加時，漏電流反而又再上升。

In this study, (Ba0.7Sr0.3)TiO3 thin films added with La, Nb and Mg ions were prepared on Pt/Ti/SiO2/Si substrate by metal-organic deposition methods (MOD). Mg-La, Mg-Nb co-doped BST films were also investigated in this work. XRD, SEM and TEM were used to characterize the effects of dopants on microstructures of thin films. The dielectric constant and leakage current of the films was also evaluated. An intermediate phase of BST films formed under annealing temperature of 600℃~650℃, but later disappeared at higher temperature. The intermediate phase was analyzed by XRD, TEM, FT-IR and Raman spectra and found to a kind of carbonate with a chemical formula of Ba2Ti2O5CO3. The stability of this intermediate phase increased with the addition of dopants, irrespective of doping types. Regarding electric properties, it was found that both dielectric constant and leakage current decreased while doping levels of single dopant (La, Nb, Mg) increased. On the other hand, for Mg-La/Mg-Nb co-doped BST films, even though the dielectric constant also decreased with increasing the doping levels, the leakage current reversed. A minimum of the leakage current occurred at Mg=5 mol%, La(Nb)=10 mol%, above that the leakage current would increase with higher doping levels.