我們將具有不同膜厚的有機場效電晶體(Organic field-effect transistors, OFETs) 在真空裝置下進行不同溫度的熱退火(Annealing)來改善電性。並利用聚亞醯胺層(polyimide, PI)做為修飾層(modification layer)。OFETs熱退火的溫度分別為70和120度，OFETs中五環素(pentacene)有機半導體層(Organic semiconductor layer)的厚度分別為50、100、300、700和1000 Å。除了電性量測外，亦將樣品表面進行X-ray繞射，原子力顯微鏡(AFM)及拉曼散射光譜(Raman spectrum)分析。元件熱退火後除了載子移動率(mobility)有提高外，臨界電壓(threshold voltage, VT)亦向正向偏移。由X-ray繞射結果指出熱退火可以改善晶格的有序度(ordering)，並可計算d-spacing，顯示在不經過熱退火下不同膜厚的五環素分子成膜初期幾乎與介電層表面垂直，在五環素膜厚超過300 Å之後則勢趨於穩定，與z軸的夾角大約在16° - 20°，經過熱退火後傾斜角則趨於穩定。最後在拉曼散射光譜觀察到1371 cm-1訊號的不對偁比(asymmetry ratio, ASR)降低，顯示熱退火後五環素分子的結晶環境有所改善。
關鍵字：五環素、有機場效電晶體、載子移動率、熱退火

In order to improvement electrical characteristics of pentacene-based field-effect transistors with different thickness pentacene films were annealed in a vacuum chamber. Organic field-effect transistors (OFETs) using polyimide (PI) as a modification layer were fabricated on a p-type silicon substrate. The annealing temperatures are 70 and 120 ℃. Pentacene films of 50, 100, 300, 700, and 1000 Å were deposited to investigate annealing effect on early stages of pentacene film growth. The surface morphology and structure of the films were examined by atomic force microscopy and X-ray diffraction spectroscopy. The threshold voltage (VT) of OFETs moves to positive and enhances carrier mobility after annealing the devices. The XRD data reveal that pentacene molecules of the first few layers are nearly perpendicular and molecules of the following layers are tilted-standing to the modification layer in the room temperature. The tilt angles of pentacene molecules are thickness independent and maintained approximately at 16°-20° after thermal annealing. Finally, we focus on analyzing the peak of 1371 cm-1 in the Raman spectrum. The reduction of asymmetry ratio (ASR) for the peak indicates an improved microstructure after thermal annealing.
Keywords: pentacene, OFETs, mobility, annealing

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