探討五環素有機薄膜電晶體之製作及電特性

有機薄膜電晶體主要是應用在平面有機顯示面板中，做為有激發光顯示器的開關電路或驅動器使用。雖然有機薄膜電晶體具有低溫製成、低成本、可製作在可撓曲之基板及可生物分解的好處，它的高操作電壓及低電子移動率使得有機薄膜電晶體能在實際應用之前仍有相當的改進空間。所以本論文中主要探討有機薄膜電晶體在不同情形下的特性。我們以五環素(Pentacene)這種有機材料為主動層做為有機薄膜電晶體。整個元件主要分四層:閘極金屬層，閘極介電層，有機主動層及汲極、源極金屬層。並以Ｘ光繞射(XRD)，原子力顯微鏡(AFM)，半導體參數測試系統(HP 4155C)等量測儀器來分析有機薄膜及整個元件的特性。並由這些特性我們可以計算出電洞位移率，並解釋在不同條件下電洞位移率變化的可能原因。首先，改變不同的基板溫度，來探討pentacene在不同基板溫度下對電洞位移率和薄膜特性的影響。由實驗結果發現，電晶體的電特性確實會受到基板溫度之影響，其中在基板溫度80 ℃時，有最好的電洞位移率可達1.30 ×10 – 3 cm2/Vs，開關電流比為4.26 × 10 3，薄膜結構也有較好的平整性和結晶性。此實驗中也發現，加熱源升溫速率增加時，位移率也有增加的現象，當加熱源溫度上升到7℃/min時，最佳的位移率可達5.32 ×10 - 3 cm2/Vs，開關電流比為2.26 × 10 4 ，subthreshold slope達到3.99 V/decade。另依各實驗是在固定加熱源的升溫速率下，變化不同的基板溫度，結果得到最佳的位移率，可達到8.56 ×10 - 3 cm2/Vs，on/off current ratio 為2.29 × 10 4 ，Vt為- 6 V，subthreshold slope提升至3.43 (V/decade)，結晶粒子也有明顯增大。綜合以上結果，我們得知基板溫度和加熱源升溫速率對元件特性和薄膜特性有很大的影響。

關鍵字

薄膜電晶體；五環素；場效位移率

並列摘要

The main application of organic thin film transistor is in flat organic display as driver or switching devices for organic light-emitting devices. Although organic thin film transistors have the advantages of low cost, low manufacturing temperature, being able to fabricated on flexible substrate, and being biodegradable, they suffers from high operating voltages and low electron mobility. These problems with the organic thin film transistors make them yet apply to practical applications. So in this thesis, we study the performance of OTFTs fabricated with different conditions. We fabricate the organic thin-film transistors (OTFTs) with pentacene organic material as a active layer. This device has four layers: gate electrode, gate dielectric layer, organic active layer, and drain/source electrodes. And we used X-ray diffraction, atomic force microscope (AFM), and semiconductor parametric test system (HP 4155C) equipments to analyze the properties of organic thin film and the performance of the device. From these properties we can calculated the hole mobility and explain the possible reasons that affect hole mobility. In the beginning, the effects of various temperatures of the substrate on the mobility and thin film properties of pentacene TFT have been investigated. It is found that the electrical characteristics of pentacene TFT depend on the temperature of substrate. The optimal mobility and on/off current ratio are 1.3 × 10 – 3 cm 2/Vs and 4.26 × 10 3 at VD = - 50 V, respectively, at substrate temperature of 80 ℃. The morphology of pentacene thin film gets smooth and crystal structure. Moreover, the mobility of pentacene OTFT increases with increasing the evaporating rate of evaporation. The best mobility, on/off current ratio, and subthreshold slope at the evaporating rate of 7 ℃/min can be obtained 5.32 × 10 – 3 cm 2/Vs, 2.26 × 10 4 and 3.99 V/decade, respectively. Finally, studies on the performance of pentacene OTFT fabricated with various temperature of the substrate. The optimal mobility, on-off current ratio, threshold voltage, and subthreshold slope of pentacene OTFT are 8.56 × 10 – 3 cm 2/Vs, 2.29 × 10 4, - 6 V, and 3.34 V/decade, respectively, with substrate temperature of 50 up to 80℃during evaporating temperature of 280 up to 350 ℃. To summarize the result, the characteristics of device and the morphology and crystallinity of pentacene thin-film depend on significantly the temperature of substrate and evaporating rate of pentacene.

並列關鍵字

field-effect mobility ； Pentacene ； Thin-film transistor

參考文獻

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探討五環素有機薄膜電晶體之製作及電特性

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