本實驗使用分子束磊晶系統，在不同晶相的基板Al2O3(11-20)與 Al2O3(0001)上成長氧化鋅摻雜鈷多層膜([ZnO20Å/Co1Å]25)，此兩組樣品的成長溫度、壓力、鍍率都盡量控制在相同條件之下。
由RHEED與XRD實驗結果證實，使用不同晶相的基板能夠得到具有不同結構的樣品：(1)Al2O3(11-20)基板能夠得到高品質的單晶薄膜，(2)Al2O3(0001)基板則會得到缺陷較多的雙晶薄膜。此外，藉著各種磁電性量測工具(SQUID、XAS、Hall effect)，得知缺陷較少之單晶薄膜自由載子濃度較高(約1.16×10^20 [1/cm3])，室溫鐵磁訊號微弱；缺陷較多之雙晶薄膜自由載子濃度較低(約4.38×10^19 [1/cm3])，卻具有較明顯的室溫鐵磁訊號。
故證實氧化鋅摻雜鈷多層膜的缺陷多寡的確與室溫鐵磁性有很強的關聯性，且本實驗之單雙晶樣品的缺陷差別大多以晶界為主。

In this study, we have grown [ZnO20Å/Co1Å]25 on Al2O3(11-20) and Al2O3(0001) substrates in Molecular Beam Epitaxy (MBE) system. The samples grown on these two types of substrates are carrier out in the same growth conditions (growth temperature, deposition rate, and working pressure).
The investigation of RHEED and XRD are concluded as follow：(1)High quality single crystal thin film (SC) grown on Al2O3(11-20) ; (2)Bi-crystal thin film (BC) grown on Al2O3(0001). This result also can imply that defects of SC should be less than these of BC. Furthermore, from the results of SQUID, XAS and Hall effect, we know that room-temperature ferromagnetism of SC with higher free–carrier concentration (Nc~1.16×10^20 [1/cm3]) is weaker than that of BC with lower Nc (~4.38×10^19 [1/cm3]).
So, we found that room-temperature ferromagnetism of Co-doped ZnO multilayer is strongly correlated with structure defects. The main difference of defects between SC and BC should be grain-boundary defects.

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