原子層沉積之氧化鎳薄膜及其應用研究

Abstract

近年來，二氧化鎳之性質受到廣泛研究。由於特殊的半導體電性以及光學性質，已有許多研究使用各種方法製備二氧化鎳薄膜於多種應用中。 在本研究，我們使用原子層沉積技術來製備二氧化鎳薄膜，藉由調控製程溫度與其他參數以得到穩定成長且均勻的氧化鎳薄膜。由各種薄膜性質分析可得知，本研究所製備的氧化鎳薄膜之雜質含量低，且載子濃度也較其他製程所製備之氧化鎳低。此外，X光繞射顯示薄膜具有結晶性。經由表面形貌分析可得知此氧化鎳薄膜表面平坦且包覆性良好。在光學性質方面，厚度六奈米之薄膜可在可見光波長範圍內穿透率達95%以上，顯示出此氧化鎳薄膜具有高穿透度。最後我們將此氧化鎳薄膜分別應用於電阻式記憶體、有機太陽能電池、以及薄膜電晶體中。在電阻式記憶體中，氧化鎳可成功地呈現雙極電阻轉換，高電阻態與低電阻態之電流比達102。但由於此薄膜缺少缺陷及氧空缺，觀察到元件在操作及參數具有不穩定之現象。另外將氧化鎳作為有機太陽能電池之電洞傳輸層，量測可得光轉換效率達2.8%，顯示此氧化鎳薄膜與PEDOT:PSS同樣具有良好的電洞傳導效果，並可阻擋電子以減少漏電流。最後我們將氧化鎳薄膜用於薄膜電晶體中的半導體層，但元件並無法展現電晶體之開關特性，推測其原因應與低載子濃度有關。 此論文研究結果分析了原子層沉積之氧化鎳的各種性質，並將其應用於光電元件中，就元件的表現與其薄膜性質加以討論，結合原子層沉積之氧化鎳薄膜的特性，歸納出其於各種應用的優缺點。

In recent years, nickel oxide has been intensively studied as a promising p-type semiconductor in wide range application. In this study, we utilized atomic layer deposition to prepare NiO thin films from Ni(amd) and H2O as precursors. From a variety of analysis, the crystalline structure, element composition, surface morphology, and optical property were studied to characterize the ALD NiO film. Furthermore, we demonstrated that the ALD NiO can be used in resistive switching random access memory (RRAM) and organic solar cell. The NiO showed the ability of bipolar switching with adequate LRS/HRS current ratio of 102. However, we found that the defect deficient ALD NiO had a poor operation stability. In addition, we used the ALD NiO as an anode interfacial layer to fabricate bulk heterojunction solar cell. The device performance indicated that ALD NiO could effectively transport holes while blocking the electron to reduce leakage current. Finally, we attempted to use NiO as p-channel materials of thin film transistors (TFT). However, the devices malfunction, which could be a result of the low hole concentration of ALD NiO. These results gave a further understanding of properties of ALD NiO and also demonstrated the ability for ALD NiO to be incorporated in various applications.