本研究受閘極感應機制啟發，而設計新型可撓式「1T1R」光訊號放大感測器以解決微縮化和低溫製程條件下訊號強度不足的問題。為了實現1T1R概念於可撓式感測器上的應用，我們選擇可彎曲、低製程溫度(<350oC)的硒化銻(Sb2Se3)作為光感材料。利用低溫蒸鍍以及電漿輔助化學氣相反應(PACVR)技術，製備寬帶光波長(λ= 350~1000 nm)偵測、高光暗電流比(Iphoto/Idark>1000)、快速反應時間(rising/falling time ~ 0.2sec)之光感材料於可撓式基板上。但隨著面積的微縮化，光訊號強度無可避免地受到限縮。為了放大感測訊號，我們採用低熱預算雷射結晶、退火與雷射光反射緩衝層技術直接製作高載子遷移率（50~100 cm2/V s）及CMOS兼容性的可撓式多晶矽電晶體，利用該電晶體所具備之高電流開關比(on/off ratio >105)、低次臨界擺幅(subthreshold slope ~ 200mV/dec)之優秀電晶體特性，增益因微縮化而被犧牲的訊號強度。
本論文比較可撓式硒化銻1T1R光訊號放大感測器在亮/暗環境下電容耦合的差別，探討感測器因有效電容變化而產生的閾值電壓平移現象(ΔVth ~ 2 V)。利用固定閘極電壓下極大的光暗電流比(Iphoto/Idark > 104)，成功地將原先小面積之微弱光訊號(Iphoto/Idark ~ 40)透過電晶體放大約375倍並保留原材料快速反應時間(response time ~ 0.2 sec)的特性。除此之外，可撓式1T1R光訊號放大器經過不同曲率半徑的彎曲測試，以及可靠度檢驗，其閾值變化維持穩定且保留光電特性。因此可撓式1T1R光訊號放大感測器其微縮化、增強訊號、彎曲可靠度高的特性，將是未來物聯網時代不可或缺、且極具潛力的感測器應用。

Inspired by gate sensing mechanism, this research try to design a new type 1T1R flexible photo-detector with amplified response to solve the problem of insufficient signal intensity caused by scaling down and low process temperature. To realize the 1T1R concept on flexible sensors application, we select bendable, low process temperature (<350oC) antimony selenide (Sb2Se3) as our flexible photo-detector material. Preparing by low temperature sputter process and plasma-assisted chemical vapor reaction(PACVR), we can synthesize Sb2Se3 with broadband wavelength detection(λ= 350~1000 nm), high photo/dark current ratio(Iphoto/Idark>1000) and fast response time (~ 0.2sec) on flexible substrate. However, the photo-signal intensity is inevitably limited due to area shrinkage. As a result, we adopt the low thermal budget laser crystallization/annealing process and introduce laser reflective buffer layer to fabricate flexible poly-Si thin film transistor(TFT) with high carrier mobility (50~100 cm2/V s) and CMOS compatibility. The flexible poly-Si TFT equipped with high on/off ratio (>105) and low subthreshold slope (~200mV/dec) which is beneficial to amplified the sensing signal.
In this study, we compare the capacitance coupling effect of 1T1R flexible Sb2Se3 photo-detecting amplifier in light and dark condition to explore the threshold voltage shift (ΔVth~2V) generated by effective capacitance change. Through the gigantic current difference (Iphoto/Idark > 104) under fixed gate voltage, we have successfully amplified the weak signal (Iphoto/Idark~40) about 375 times and preserve fast response time (~ 0.2 sec) property. Furthermore, by bending experiment in different bending radius and reliability test, flexible 1T1R Sb2Se3 photo-detector exhibits stable optical properties and threshold voltage shift. Such flexible 1T1R Sb2Se3 photo-detector with amplified response, scaling area, and high reliability will be a potential sensor application in IoTs era.

中文摘要----------------------------------------------------------i
ABSTRACT--------------------------------------------------------ii
誌謝------------------------------------------------------------iii
Table of Contents------------------------------------------------v
List of Figures-----------------------------------------------viii
List of Tables-------------------------------------------------xii
Chapter 1 Introduction-------------------------------------1
1.1 Flexible electronics-------------------------------------1
1.2 Flexible sensors-----------------------------------------2
1.3 Motivation-----------------------------------------------3
Chapter 2 Literature review--------------------------------6
2.1 Flexible thin film transistor----------------------------6
2.1.1 Fabrication methods--------------------------------------6
2.1.2 Materials choices----------------------------------------7
2.1.3 Low thermal budget laser technology----------------------9
2.2 Flexible photo-detector---------------------------------11
2.2.1 The development of flexible photo-detectors-------------11
2.2.2 Antimony selenide (Sb2Se3)------------------------------13
2.2.3 The mechanism of photo-detector-------------------------14
2.2.4 Performance parameters----------------------------------15
Chapter 3 Experimental and Analytical Instruments---------17
3.1 Process instruments-------------------------------------17
3.1.1 Plasma-enhanced Chemical Vapor Deposition (PECVD)-------17
3.1.2 Pulse Laser system--------------------------------------17
3.1.3 Selenization furnace------------------------------------18
3.2 Analytical instruments----------------------------------18
3.2.1 Raman spectrum analysis---------------------------------18
3.2.2 X-Ray Diffraction (XRD)---------------------------------19
3.2.3 Photoelectric measurement system------------------------19
Chapter 4 Experimental Process----------------------------20
4.1 Flexible FET fabrication--------------------------------20
4.1.1 Substrate preparation-----------------------------------20
4.1.2 Active layer fabrication--------------------------------21
4.1.3 Photolithography----------------------------------------22
4.1.4 Dry etching---------------------------------------------23
4.1.5 Gate fabrication----------------------------------------24
4.1.6 Implantation and Green Laser Activation (GLA)-----------25
4.1.7 Interconnection fabrication-----------------------------26
4.2 Sb2Se3 synthesis----------------------------------------26
4.3 Integration flow----------------------------------------27
4.3.1 Sensing area definition---------------------------------28
4.3.2 Sensor deposition and Lift-off process------------------28
4.3.3 Oxidation and Plasma assisted chemical vapor reaction---29
4.4 Peel-off process----------------------------------------30
4.4.1 UV tape and Supporting film adhesion--------------------30
4.4.2 UV light exposure---------------------------------------30
Chapter 5 Results and Discussion--------------------------31
5.1 Flexible poly-Si FET performance------------------------31
5.1.1 I-V electrical analysis---------------------------------31
5.1.2 Bending performance-------------------------------------34
5.2 Flexible Sb2Se3 characterization and photovoltaic performance-----------------------------------------------------37
5.2.1 Raman spectrum analysis---------------------------------37
5.2.2 X-ray diffraction analysis------------------------------39
5.2.3 Photo-detecting performance-----------------------------41
5.3 Integration---------------------------------------------42
5.3.1 Sensor characterization after integration---------------43
5.3.2 Characteristics changes after sensor synthesis----------44
5.4 Optoelectronic performance------------------------------45
5.4.1 Amplified photo-response--------------------------------45
5.4.2 Mechanism of 1T1R photo-detector------------------------48
5.4.3 Optoelectronics properties------------------------------51
5.5 Bending performance of 1T1R-----------------------------52
5.5.1 Characterization after peel-off process-----------------52
5.5.2 Bending in different curvature--------------------------53
5.5.3 Reliability---------------------------------------------54
Chapter 6 Conclusion and Future work----------------------56
6.1 Conclusion----------------------------------------------56
6.2 Future work---------------------------------------------56
References------------------------------------------------------58

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