本論文主要研究薄膜晶向對於氧化亞銅電阻式記憶體(RRAM)特性的影響。單一晶向的Cu2O(200)和Cu2O(111)可以由調整電鍍溶液的pH值形成，藉此探討兩者的電阻轉換特性。
單一晶向的Cu2O(200)和Cu2O(111)薄膜分別以電化學法沉積。以硫酸銅調配電鍍前驅溶液，並以氫氧化鈉溶液分別滴定至pH值9與11。根據SEM圖可發現Cu2O(200)薄膜的相較於Cu2O(111)薄膜更為垂直，而AFM分析也發現Cu2O(200)的薄膜粗糙度相較於Cu2O(111)更為平整，兩者的平均粗糙度分別為10.0 nm和36.3 nm。
進行RRAM特性測試時，兩者都不需Forming電壓，而以Cu2O(200)薄膜進行量測時，可發現Set及Reset電壓相較於Cu2O(111) RRAM更小，且電壓分布區間也較小，Cu2O(200) RRAM的Set電壓及Reset電壓分別為1.8 V至4.4 V及-0.9 V至-2.5 V，Cu2O(111) RRAM的Set電壓及Reset電壓分別為1.2 V至9.2 V及-0.9 V至-3.4 V，藉此可推論薄膜結構可能會影響缺陷密度及分布，進而影響電子在缺陷上的跳躍。當結構較為垂直時，缺陷位置會沿著晶體邊界分布，提供電子較短的跳躍路徑或只需要較低的能量就可移動。
當高阻態時，Cu2O(200) RRAM的電流相較於Cu2O(111) RRAM更小，所以使Cu2O(200) RRAM高低阻態的比值大於Cu2O(111) RRAM，從實驗數據可得知，Cu2O(200)和Cu2O(111) RRAM都可維持不錯的穩定性及耐久度。其中Cu2O(200) RRAM的高低阻態比值及資料保存力都為100倍，相反的，Cu2O(111) RRAM的高低阻態比值及資料保存力只有10倍。
根據實驗結果可知，Cu2O(200)薄膜在RRAM上有較好的競爭性，較低的Set/Reset電壓、較好的穩定性及資料保存能力。往後研究可朝減少薄膜厚度、降低功率消耗及熱穩定度等方向研究以作為往後商業應用。

This thesis studies the influence of thin film’s phase orientation on the characteristics of cuprous oxide (Cu2O) resistive random access memory (RRAM). Single phase of Cu2O(200) and Cu2O(111) crystal orientations can be formed by adjusting pH value of the electroplating solution. The resistive switching characteristics of the two films were studied.
The single phase of Cu2O(200) and Cu2O(111) films were deposited separately via electrodeposition method. The electroplating precursor solution was prepared with copper sulfate, and its pH value was adjusted to 9 and 11 via dripping of a NaOH solution, respectively. SEM images indicate that Cu2O(200) exhibit a more vertical aligned grain structure than Cu2O(111) film. The AFM dada also revealed that Cu2O (200)’s film roughness was much smoother than that of the Cu2O(111). Their average roughness was 10.0 nm and 36.3 nm, respectively.
Both of them do not need a forming process during the RRAM characteristic tests. RRAM using Cu2O(200) film has smaller set and reset voltages than that of the Cu2O(111) RRAM, as well as tighter voltage distributions. The set and reset voltages of Cu2O(200) RRAM are 1.8 V~4.4 V and 0.9 V~ 2.5 V, respectively. The set and reset voltages of Cu2O(111) RRAM are 1.2 V~9.2 V and 0.9 V~ 3.4 V, respectively. It could be inferred that structure of the film may affect the defect density and distribution that can provide electrons’ hopping. When the structure was relatively vertical, the defects located along the crystal grain boundaries may provide shorter path for the electrons to make the hop with ease or lower energy needed.
At high resistance state (HRS), the (leakage) current of the Cu2O(200) RRAM is smaller than that of the Cu2O(111). The ratio of high and low resistance states (LRS) of the Cu2O(200) RRAM is larger than that of the Cu2O(111). The data shows that both of Cu2O(200) and Cu2O(111) RRAM can maintain good stability or retention. Both HRS/LRS resistance ratio and its retention of Cu2O(200) RRAM are two orders of magnitude; In contrast to Cu2O(111) RRAM, the HRS/LRS resistance ratio and retention have only one order of magnitude. The test results of all switching characteristics indicate that Cu2O(200) film is a better candidate for RRAM film with low set/reset voltages, good endurance and better retention. Further studies of decreasing film thickness, lower power consumption and thermal stability are needed for the consideration of commercial applications in the future.

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