高分子場效電晶體型記憶體之微結構及表面改質對元件特性之影響

Effects of Microstructures and Surface Modifications on the Characteristics of Polymer Field Effect Transistor Type Memory Devices

林育威(Yu-Wei Lin)

指導教授 ： 陳文章

國立臺灣大學/工學院/化學工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.01669

摘要

高分子電晶體型記憶體元件由於可以溶液製程製備，並具有良好的撓曲性質，因此在近年來相當受到矚目。電晶體型記憶體中主要的機制乃是於高分子介電質、界面缺陷或是奈米晶體浮動閘極中的穩定電荷滯留。然而以高分子奈米纖維為基礎的非揮發性記憶體元件為主題的探討還不多，因此此碩士論文探討了不同型態導電層對記憶體性質的影響。此外也將高極性的聚啞胺介電質應用於可撓曲的非揮發性電晶體型記憶體。

1. 以靜電紡絲纖維為基礎之非揮發場效電晶體型記憶體(第二章)
此部分研究以F8T2高分子為基礎之靜電紡絲纖維場效電晶體型記憶體之非揮發性記憶體性質。其中我們探討了導電層型態以及纖維直徑對電荷流動以及電荷滯留的影響。較細小的靜電紡絲所測得的載子遷移率較高，乃是由於纖維中的較高結晶度以及堆積方向的集中程度。 較粗的靜電紡絲則因為纖維中晶相-非晶相界面較多而具有較大的記憶體操作範圍。最高的載子遷移率可達 9.8x10-3 cm2V-1s-1並且於0 Vg具有3.6x103的高低電流比。在寫入-讀取-擦拭-讀取 (WRER)測試中，電紡絲元件可以承受100次以上的反覆操作。此部份研究發現靜電紡絲中的微結構對於電荷滯留的能力以及因此產生的記憶體特性有很顯著的影響。

2. 以聚啞胺介電質為基礎之可撓曲場效電晶體型非揮發記憶元件(第三章)
此部分為使用2,5-Bis (4-aminophenylenesulfanyl) selenophene-4,4’- (hexafluoroisopropylidene) diphthalic anhydride (APSP-6FDA)以及2,5-Bis (4-aminophenylenesulfanyl) thiophene-4,4’- (hexafluoroisopropylidene) diphthalic anhydride (APST-6FDA)作為介電質、可交聯Polydimethylsiloxane (PDMS)作為阻漏層和Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-bithiophene] (F8T2)為導電層之可撓曲電晶體型記憶體元件性質探討。由於selenophene中比起thiophene有較高的電子雲密度，以APSP-6FDA為基礎的元件在寫入(writing)以及擦拭(erasing)操作之後，有高達83V之記憶體操作空間同時也有1.29x10-3cm2V-1s-1的載子遷移率，並無降低太多電荷傳輸性質。在長期穩定性測試中，高低訊號比可達105以上，並可來回寫入-讀取-擦拭-讀取超過100次，可維持10000s以上的穩定訊號。在撓曲程度上，可撓曲曲率半徑可達3mm以下仍無明顯元件電性破壞，若以曲率半徑13mm進行多次撓曲，可承受3000次以上的撓曲，同樣地無明顯電性崩潰，展現了未來應用於可攜式記憶體元件的濳力。

關鍵字

共軛高分子 ； 靜電紡絲纖維 ； 場效電晶體 ； 記憶體

並列摘要

Polymer transistor type memory devices have recently attracted significant scientific interest for flexible electronic applications due to the advantages such as low cost, solution process and flexibility. The dominant mechanism in transistor type memory is the charges trapping due to polymer electrets, interfacial defects or nano-crystal floating gate. However, the nanofibers based nonvolatile memory devices or flexible memory devices have not been fully explored yet. In this thesis, we explored the following two subjects to address the above issues: (1) nonvolatile field-effect transistor memory based on ES nanofibers. (2) flexible nonvolatile transistor memory devices based on polyimides (PIs) Electrets.

Nonnvolatile Field-Effect Transistor Memory Based on Electrospun Nanofibers　(chapter 2) : We have demonstrated the memory characteristics of ES nanofibers based on F8T2. The effects of the geometry and diameter of the ES nanofibers on charge transport and charge storage ability were explored. The narrow ES nanofibers showed higher mobility than those with a large diameter, because the improved orientation and crystallinity. The large ES nanofiber exhibited a larger memory window, attributed to the heterogeneities in the amorphous-crystalline interfaces in the F8T2 ES nanofibers. The devices of the ES nanofibers with the smallest diameter showed the highest charge carrier mobility of 9.8×10-3 and on-off ratio of 3.6×103 at Vg = 0 V. From the stability testing of the WRER cycles, the good on/off ratios could be maintained for at least 100 cycles, showing good stability. This study demonstrated that the morphology of ES nanofibers have a significant influence on electrical charge storage ability and their resulted memory characteristics.

Flexible Nonvolatile Transistor Memory Devices Based on PIs Electrets (chapter 3) : OFET memory devices were fabricated with 2,5-Bis (4-aminophenylenesulfanyl) selenophene-4,4’- (hexafluoroisopropylidene) diphthalic anhydride (APSP-6FDA) and 2,5-Bis (4-aminophenylenesulfanyl) thiophene-4,4’- (hexafluoroisopropylidene) diphthalic anhydride (APST-6FDA) as the electrets, c-PDMS as the blocking layer and F8T2 as the conducting layer. The wider memory operation window (83V) and higher hole mobility (1.29x10-3 cm2V-1s-1) were observed in APSP-6FDA based devices than those of APST-6FDA based devices attributed to the higher electron density in selenophene than thiophene. Moreover, retention test and WRER test showed a long term stability at least 10000s and durability for repeated operation more than 100 cycles. During the bending test of various curvature radius and repeated bending, the hole mobility could be kept in the same level as that in flat state until r = 3 mm and can maintain at least 3000 bending cycles under the curvature r =13 mm. The threshold voltage shift was also kept in a similar level after 3000 bending cycles and increased considerably when curvature radius was smaller than 3 mm, due to more interface defects after the hard bending. The above results demonstrated the potential applications of the materials for flexible nonvolatile memory devices.

並列關鍵字

electrospun nanofibers ； transistor-type memory

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