本研究以金屬鈦(Titanium, Ti)為上下電極，氧化亞銅(Cuprous oxide, Cu2O)為介電層，利用磁控濺鍍將薄膜沉積於玻璃基材上，並製作出不同中間層厚度之Ti/Cu2O/Ti三層結構電阻式記憶體，探討元件退火後的結構與電性之影響。
Ti/Cu2O (130 nm)/Ti元件經過forming可作電阻切換達700次以上，且高低電阻比約達8倍，為可穩定操作之電阻式記憶體。而Ti/Cu2O (130 nm)/Ti元件退火後不需要forming，高低電阻比達56倍且可穩定操作100次。經由結構與成分分析發現，在Ti上下電極靠近Cu2O之交界有TiOx界面層形成，並且在退火後Cu2O中有Cu晶粒還原出，因此降低元件中Cu2O的膜厚，希望藉此能讓Ti/Cu2O/Ti元件在退火後轉變為Ti/TiOx/Cu/TiOx/Ti之結構，製作出互補電阻式記憶體。
在Ti/Cu2O (25 nm)/Ti元件中，元件之傳導機制與電阻切換特性隨著電壓多次來回掃描而改變，初始元件呈現以高電阻態為SCLC，低電阻態為Ohmic conduction之雙極式電阻記憶體；經過多次掃描後轉變成“0”和“1”為Schottky emission，“ON”為Ohmic conduction之CRS元件。而退火後之Ti/Cu2O (25 nm)/Ti元件為穩定之CRS元件，可穩定操作達80次，且其 “ON” window中之高低電阻比約9倍。經由結構與成分分析發現，Ti/Cu2O (25 nm)/Ti退火元件內中間層之Cu2O已被還原成Cu，而Cu與TiOx之接觸為Schottky contact，可解釋在 “0”和“1”之狀態下傳導機制為Schottky emission；改變溫度測試之結果則可推斷低電阻態為銅燈絲傳導之Ohmic conduction。
最後利用製作Cu/TiOx/Ti之電阻式記憶體進行電性量測與導電機制分析，並且發現與Ti/Cu2O (25 nm)/Ti退火元件分析之結果相同，證明Ti/Cu2O (25 nm)/Ti元件經退火後已轉變成Ti/TiOx/Cu/TiOx/Ti之互補電組式記憶體。

In this study, we used titanium (Ti) as the top and bottom electrode, cuprous oxide (Cu2O) as the dielectric layer to fabricateTi/Cu2O/Ti RRAM device by magnetic sputtering process. We also analyzed the structure and electrical properties of the devices with different thickness of Cu2O.
After a forming process by applying a positive bias, the as-prepared Ti/Cu2O (130nm)/Ti device could switch in high resistance state (HRS) and low resistance state (LRS) over 700 times by bipolar switching. The ratio between two resistance state was about 7.5. However, the annealed Ti/Cu2O (130nm)/Ti device could normally operate without a forming process and exhibited the ratio of HRS to LRS about 53 during 100 cycles of testing. By the structure and component analysis, it was found that Cu grains formed in the Cu2O layer and a TiOx interface layer formed between the Ti electrode and the Cu2O. Therefore, we reduced the thickness of Cu2O in Ti/Cu2O/Ti device in order to obtain Ti/TiOx/Cu/TiOx/Ti CRS device after vacuum annealing process.
The resistace switching was unstable in the as-prepared Ti/Cu2O (25nm)/Ti device, and the mechanism of conduction was changed after doing several I-V cycles. At first, the device exhibited bipolar resistive switching and it showed SCLC in HRS and Ohmic conduction in LRS. And it turned into complementary resistive switching (CRS) with Schottky emission in “0” and “1” state while “ON” state was still Ohmic conduction. On the other hand, the annealed Ti/Cu2O (25nm)/Ti device showed good stability as a CRS device. The raio of the high resistance “0” and “1” to low resistance in the “ON” window was about 9 during 80 times of operation. And the mechanim of “0” and “1” state were Schottky emission due to the Schottky contact betwee Cu and TiOx. For the mechanism of “ON” state, we carried out electrical measurements at various temperatures and found that the resistance increased with increase temperature. It suggested that Cu was an active electrode and provided Cu filaments for the carriers to transport.
We also prepared Cu/TiOx/Ti RRAM device to analyze the electrical properties and elucidated that it’s one of the cells in Ti/TiOx/Cu/TiOx/Ti CRS device. In other words, we proved that Ti/Cu2O/Ti becomes Ti/TiOx/Cu/TiOx/Ti after vacuum annealing process.

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