本研究使用電漿輔助化學氣相還原法，在低溫下製備出具有垂直層狀結構的二硒化鉬材料，並將此材料作為電阻式記憶體中的電阻變化層。
二硒化鉬屬於過鍍金屬二硫化物(TMD)類別，在二維材料的發展中有很大的佔比；過往關於二硫化鉬與二硫化鎢有許多傑出的研究，就相轉換的角度而言，二硒化鉬較前面兩者具備更低的轉換能障。此研究著力於相轉換貢獻在電阻式記憶體的電性表現上。使用電漿輔助硒化系統的目的，在於其有效降低製程溫度，減少基板熱損害，不需要材料轉移可直接製造元件。同時，後硒化製程在於厚度上可以做到大面積均勻可控，可以從前驅氧化物鍍膜厚度做改變。
透過垂直於層狀結構的電場所導致的金屬離子的嵌入，使得離子流動產生之合力給予層間壓縮力，縮減材料層間距，由富1T的混合相轉變為2H相，而當反向偏壓施加時，則為鬆弛壓力，層間距恢復，轉為原先富1T的混合相。
在金屬離子之中，銅的特殊性也加入討論，包括銅對降低相轉換能障的幫助，硒化銅薄層對於銅嵌入的影響。此研究顯示離子移動產生的相轉換與對應電性，元件表現上可以穩定操作100個迴圈，高低電阻比達1個數量級，耐久度測試達20,000秒；並且於脈衝電性量測顯示有類神經網路硬體端應用的潛力。
本研究提出過鍍金屬二硫化物族作為未來先進製程發展的重點材料，於記憶體元件應用的可行性，以及同步輻射光源輔助原理驗證，有助於未來相關研究的構想與發展。

Resistive random access memory (ReRAM) records 0 and 1 signals by varying conductance states of the middle layer in a MIM structure. And it has the merit of lower programming currents without sacrificing programming performance, retention or endurance. Devices applying synapse-mimicking concepts have attracted impressive attention recently. In an analogue computing neurocomputer, memristors can act as neurons separately and also play as the synapses which are the joints between neurons. By which energy consumption can be reduced and computation speed can be enhanced. Previous studies showed that transition metal dichalcogenides can be one of the candidates of the host material for ionic modulation to take place. Because TMDCs are stacking of two dimensional layers and there is only van-der-Waals force in between, intercalation between layers will cause structural and conductance change between the semiconducting hexagonal (2H) structure and metallic tetragonal (1T) one. However, most of the intercalations are carried out by immersing in organolithium reagent and current-voltage (I-V) measurement can only be conducted in the glove box. In this study, all the measurements can be done under atmospheric environment by an all-solid-state process including ions intercalation. Molybdenum selenide (MoSe2) patterns were synthesized by a specially designed selenization chamber assisted by plasma under low temperature, which decreases heat damage and reaches nowadays electronics requirements for low processing temperature. By using unsymmetrical electrodes design, electric field induces active metal ions into MoSe2 lamellar structure and change local arrangement thus have conductivity variation. Using different bias condition, ions will migrate and different local distribution of 1T and 2H can take place. When applying DC bias, this work shows great endurance of more than 100 cycles, high stability for retention test (more than 104 s) and an on-off ratio about 900%. In pulsed measurements, the conductivity in MoSe2 will gradual increase and will depotentiate conversely.

ABSTRACT (CHINESE) I
ABSTRACT (ENGLISH) II
CONTENTS III
FIGURE CAPTION V
TABLE CAPTION XI
CHAPTER 1 INTRODUCTION 1
1.1 TRANSITION METAL DICHALCOGENIDES (TMDCS) 1
1.1.1 Composition and crystal phases and electronic structure 1
1.1.2 Optical and vibrational properties 4
1.1.3 Manufacturing process of TMDCs 6
1.1.4 Intercalation and Cu adsorption induced phase change 12
1.1.5 Force induced phase change 18
1.1.6 XAS analysed phase change 20
1.2 TMD RESISTIVE RANDOM ACCESS MEMORY 21
1.2.1 Overview of memory 21
1.2.2 Metal oxide vs. TMDCs 22
1.2.3 TMDCs memory 24
CHAPTER 2 MOTIVATION 30
CHAPTER 3 EXPERIMENTAL DESIGN 33
3.1 FABRICATION OF MOSE2 34
3.2 ELECTRODES PATTERN DESIGN 38
3.3 IV MEASUREMENT 40
3.4 ANALYSIS TECHNIQUES 41
3.4.1 Raman spectroscopy 41
3.4.2 Electron microscope analysis and XPS 42
3.4.3 SPEM analysis 42
3.4.4 XAS spectroscopy 43
CHAPTER 4 RESULTS AND DISCUSSION 45
4.1 MATERIALS CHARATERIZATION ON MOSE2 SYNTHESIS 45
4.2 OPTIMIZATION OF RERAM PERFORMANCE 48
4.2.1 Comparison on phase difference 48
4.2.2 Comparison of inert and active metals 49
4.2.3 Copper intercalation 50
4.2.4 Comparison on lamellar direction 54
4.2.5 Performance discussion 55
4.3 MECHANISM DISCUSSION 58
4.3.1 Synchrotron radiation analysis 58
4.3.2 TEM analysis 61
4.3.3 Effect of work function on IV behavior 66
4.4 APPLICATION ON NEUROMORPHIC COMPUTATION 68
CHAPTER 5 CONCLUSION AND OUTLOOK 71
CHAPTER 6 REFERENCE 73

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