本文利用射頻磁控濺鍍法沉積五氧化二釩薄膜，討論在不同製程條件下薄膜的特性，並將此薄膜作為主動層應用於電阻式隨機存取記憶體中，研究元件開關電特性探討。
首先以磁控濺鍍法在不同的製程條件下沉積五氧化二釩薄膜，並從四方向去討論氧化釩薄膜特性，分別是薄膜結構特性、薄膜光學特性、薄膜表面和縱深分析，以及薄膜熱電阻值分析。在結構特性上，氧化釩薄膜表面緻密且隨溫度上升有晶相產生。而在光學特性的部分，由於釩的能隙較小，有釩成分存在於薄膜時，使得薄膜成為一種低能隙的材料，主要吸收可見光波段，接著從熱實驗量測中證實，氧化釩薄膜為過渡金屬材料，具備金屬絕緣轉換機制，當薄膜經熱退火後，由TCR四點探針量測系統可見，當溫度高於攝氏60度時，可觀察電阻值變小，驗證熱對於氧化釩材料有一定程度的影響，進而推斷氧化釩是一種熱電材料。
根據X光繞射分析儀(XRD)圖得知，薄膜經熱退火溫度250℃時，峰值有最強晶相(001)，接著透過X射線光電子能譜（XPS）圖得知，薄膜中的氧空缺會由於製程中氧氣通入量以及特定回火溫度有所變動而有最佳參數。最後，為了能確切得知元件結構厚度，我們使用穿透式電子顯微鏡(TEM), 並從能量分散式光譜儀(EDS)得知各材料的組成原子比，並藉由原子力顯微鏡(AFM)量測，表面態密度越低使得薄膜表面越平滑，有助於改善元件表現。
另一部分，本論文以W針/V2O5/Pt為架構電阻式隨機存取記憶體的製備方法與電特性探討，透過不同尺寸鎢針作為上電極製備記憶體，分析1μm以及5μm鎢針對於元件差異，兩者接能夠完成超過100次的操作開關元件，並且在0.1伏電壓下，有著超過10000秒的穩定記憶特性，以及具備雙極性電阻轉換特性。接者分析電流-電壓特性曲線，可以探討載子的傳導機制；在Set過程中，上電極施加正偏壓，使得主動層中薄膜的氧空缺排列形成導電燈絲，起初電壓電流呈現一次線性關係，初始為歐姆接觸(Ohmic)機制，接著逐漸增加電壓，電流反而趨漸平緩且與電壓平方成正相關，此傳導機制進入空間電荷限電流層(SCLC)，最後當開路電壓到達VSet，導電路徑成功形成，元件進入導通電流態。相反地，當上電極施加負電壓時，電子注入薄膜與氧空缺結合，而當關閉電路到達VReset時，代表有足夠氧化還原能力，使得導通燈絲斷裂，元件回復到初始高阻態薄膜。
最後，為了達到更小的開關路電壓，以及更穩定的高阻態與低組態之穩定性，我們研究以銀作為上電極之Ag/V2O5/Pt結構之電阻式記憶體開關元件。製備完成的元件，一樣表現出雙極性電阻轉換特性外，並有效降低開關電壓，且維持優良的記憶體開關比。主要是因為銀為高自由能材料，銀原子能擴散至薄膜內，當施加正偏壓下快速形成銀導通路徑，使得薄膜阻值處於低阻態位，反之當負偏壓施加後，銀原子經氧化還原後導通路徑斷裂，元件回復至高阻態，這意味著在不接觸薄膜表面下，銀電極不僅保護氧化釩表面並有著改善記憶體特性的重要方法之一。

In this thesis, vanadium pentoxide (V2O5) is deposited by RF magnetron sputtering and the films’ properties are discussed thoroughly under different ambiences. Next, we will apply V2O5 thin films in Resistive Random Access Memory(RRAM) device to search electric characteristics and on /off switching performance.
First, we utilize the RF-sputtering system to grow thin film with different condition and the films’ properties are researched into four aspects which are structural, optical analysis, surface/depth element analysis, and thermoelectric resistance transition analysis. The films are amorphous as-deposited and the crystalline phase gradually appears with the increasing of the annealing temperature. For the optical analysis, owing to the small bandgap of Vanadium, V2O5 thin films could be used as narrow bandgap material, absorbing in visible light. Since the heating experiment, we could observe the Vanadium oxide thin films, which is a transition metal with Metal-Insulator Transition (MIT) characteristics. Owing to measuring analysis of the heating temperature with the four probes of TCR analysis. When the temperature is over 60 degrees Celsius, the films resistance sharply decreases. The result proves that heating ambience impacts on the Vanadium material, and we could furtherly define vanadium oxide is a thermoelectric material.
According to X-ray diffraction (XRD) analysis, the crystal phase corresponds to stronger phase (001) under annealing 250℃ ambience. Next, the XPS shows that the oxygen vacancies will be filled up with adjusting the best oxygen flow ratio and specific annealing temperature. For surface/depth element analysis, the TEM measurement could provide the accurate thickness and element dispersive spectrometer (EDS). Finally, we could observe the smooth surface of the films by AFM measurement. The results discuss the smooth surface with lower surface density of states, which is beneficial for the performance of the devices.
In the second part of experiment, we fabricate the W-probe/V2O5/Pt and analyzed of the RRAM cell with different size of 1μm & 5μm W-probe electric performance. The fabricated device demonstrates over one hundred DC switching times and displays stable retention test for over 104s under 0.1 V stress that appears bipolar switching behavior. With I-V curves fitting method, we could find the conductive mechanism of the devices. While set process is firstly dominated by Ohmic conduction with stressed positive voltage, current is proportional to applied voltage and then forced the oxygen vacancies to grow up conductive filaments. Later, the current flatted happens at increasing the electric voltage, which transforms to the space charge limited conduction (SCLC) and changes current’s proportional to square of applied voltage in the high resistance state. Finally, conduction filaments successfully form and turn into low resistance state when applied voltage sweeps to VSET. On the contrary, the electron injects to fill up the oxygen vacancies by stressed negative voltage. As the off voltage is VRESET, which represents with stronger reduction-oxidation effect to cut down the filaments. This phenomenon causes to the film back to the high resistance state.
Finally, in order to improve lower On/Off sweep voltage and stabilize high resistance state and low resistance state, we investigate the characteristics of top electrode structure: Ag/V2O5/Pt RRAM device. The fabricated device shows bipolar switching behavior as well. With stronger free energy, Ag atom could diffuse into the surface of thin film. As stressing the positive voltage, the Ag conductive bridge occurs to LRS. Conversely, compressing the negative voltage, Reduction-oxidation action forces to Ag atom returned back to the thin surface. The conductive bridge also breaks, so the film is back to HRS. It means Ag top electrode not only protects vanadium oxide film without contacting directly, but optimizes further on/off voltage and maintains good ratio of HRS/LRS. The Ag/V2O5/Pt structure reveals an important method to improve the characteristics of RRAM devices.

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