本論文利用物理氣相沉積將鋁成長100 nm在玻璃基板上，再以高真空氧電漿蝕刻系統(O2-plasma)於鋁上形成高介電值(high-K)之氧化鋁絕緣層，以降低有機薄膜電晶體的門檻電壓(threshold voltage；VT)。選用型號為7013的聚醯亞胺(polyimide；PI)作為載子捕捉層(charge trapping layer)，因其具有優異的絕緣性與良好的機械、化學性質，且能使有機半導體的長晶更佳。再使用N-甲基-吡咯酮(N-Methyl pyrrolidone；NMP)稀釋PI，並以固含量表示成6.3 wt%、4.7 wt%、3.2 wt%與1.6 wt%。PI也同時為駐極體(electret)，其分子結構上具支鏈，會在外在的電場影響下，改變分子的排列方向並形成電偶極，可增強場效，加強捕捉載子能力。最後利用PVD成長80 nm 的N型有機半導體十三烷基駢苯衍生物(N,N’-ditridecylperylene-3,4,9,10-tetracarboxylic diimide；PTCDI-C13H27)作為傳輸載子之主動層，再鍍上80 nm銀為汲極與源極的電極，做出N型低電壓操作的有機非揮發性電晶體式記憶體(organic non-volatile transistor-type memory；ONVM)。
在薄膜分析的部分，利用接觸角分析儀分析不同固含量PI之表面能，可知PI為1.6 wt%時，其非極性項最小，但極性項最大，有較強的場效能力，使元件有最大的通道飽和電流。由掃描式開爾文探針顯微鏡(scanning kelvin probe microscopy；SKPM)分析結果表明，當PI的固含量改變時，其薄膜表面的電位不會有太大的差異，且薄膜表面電位分布均勻，表示其形成連續薄膜。利用原子力顯微鏡(atomic force microscopy；AFM)得知PI為1.6 wt%時表面粗糙度最大，但載子捕捉層薄膜的厚度最薄。再以X光繞射儀(x-ray diffraction；XRD)觀察到PTCDI-C13H27 成長於1.6 wt% PI上之結晶相較不明顯，其繞射波峰峰值較低且半高寬(full width at half maximum；FWHM)較小。
在有機薄膜電晶體之電性方面分析結果顯示，在不使用PI的有機薄膜電晶體中，其氧化鋁介電層無法有效地阻擋從閘極端的漏電流，使元件無法操作於1 V以上的電壓。過大的操作電壓會使元件的漏電流增大，穿透氧化鋁介電層使通道電流大幅上升，進一步使元件崩潰。而使用PI的有機薄膜電晶體，能輔助高介電質的氧化鋁阻擋漏電流的發生，更能使元件操作電壓上升至3 V，並增加元件的通道電流。在1.6 wt% PI時，擁有較低的門檻電壓與次臨界擺幅，較大的電容值、電流開關比與載子遷移率。推測主要原因為載子捕捉層厚度降低至24 nm，能有效增強場效的能力，使元件的通道電流值增大。
本論文的有機記憶體元件利用給予閘極之脈衝電壓(pulse voltage)，使門檻電壓產生偏移。在記憶體元件特性分析結果顯示，不同固含量PI的記憶元件操作在3 V的閘極電壓時，皆可得最大記憶窗口。但在過高的脈衝閘極電壓下，有機記憶元件的介電層無法阻擋過強的電壓，會在一瞬間有過大的漏電流造成元件的崩潰。但在6.3 wt% PI時，由於載子捕捉層厚度為136 nm，造成閘極電壓的場效影響下降，降低載子捕捉的能力，記憶元件僅有0.1 V的記憶窗口。在進行記憶元件的操作時，可同時使用綠光雷射(λ = 533 nm)輔助清除，因有機半導體主動層PTCDI-C13H27之吸收光譜為綠光波段。在給予負閘極脈衝電壓清除的同時照射綠光雷射，可提供大量電子電洞對，幫助釋放被有機半導體層與載子捕捉層的介面陷捕能態所捕捉的電子，增大記憶窗口。利用綠光雷射輔助清除1.6 wt% PI的記憶元件，其記憶窗口能達到0.7 V。記憶元件的記憶保持度方面，由電壓偏移大小可判斷記憶元件寫入能力，可以發現載子捕捉層厚度低，捉捕電子能力較強。故PI固含量為1.6 wt%的記憶元件進行寫入並等待兩小時後，門檻電壓值僅下降0.2 V，說明了良好的記憶保持度。經過50次的寫入與清除，1.6 wt% PI的記憶元件仍能保有0.6 V的記憶窗口，證明記憶元件有良好的記憶耐久度。在元件的穩定度測試中，由於PI固含量為1.6 wt%的記憶元件缺陷能態密度最大為3.63 × 1012 / cm2 eV，有機半導體中的載子要不斷地填補缺陷能態密度，造成元件的通道電流會隨著時間而下降，待填補完缺陷能態後，元件的通道電流才會逐漸穩定。

In this study, we used high-K materials, aluminum oxide, as a dielectric of organic thin-film transistors (OTFTs) to reduce the threshold and operating voltages. Polyimide (PI) was applied to n-type OTFTs as both insulator and electret in order to improve electrical characteristics and memory windows of OTFT-based memories. The electrical characteristics of the devices and the properties of PI films with various solid contents were measured by electrical and capacitative analyzers.
According to the electrical characteristics of OTFTs, the devices without PI showed large leakage current (gate current). The devices with PI performed enhanced channel current as well as low and stable gate current. Furthermore, we used different solid content of PI solutions to modulate the properties of PI layers. We observed that thinner PI film increased gate electric field to enhance carrier accumulation in n-type N,N’-ditridecylperylene-3,4,9,10-tetracarboxylic diimide semiconducting layer, improving the channel current of OTFTs. Based on the results of electrical measurements of devices, the OTFT-based memory devices with a PI layer spin-coated from 1.6 wt% solution have more trap states exiting in the interface between the PI and the active layers of devices, compared with those from other solid content of solutions.
The OTFT-based memory devices displayed a good retention of memory window under continuous operation. Moreover, the memory window of the device with PI layer from 1.6 wt% solution only decreased 16% after 2 hours’ operation. Surprisingly, a 500% increment of memory window of memory device was achieved by assisting a green laser beam during device operation. In summary, we have successfully fabricated a low-voltage operated organic memory device, in which the memory window has potential in industry production.

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