【摘要】：有機(jī)薄膜晶體管憑借其加工工藝過(guò)程簡(jiǎn)單、制造成本低廉、有望實(shí)現(xiàn)柔性卷到卷(roll-to-roll)大面積生產(chǎn)等特點(diǎn),已在柔性顯示、柔性存儲(chǔ)、射頻識(shí)別(RFID)標(biāo)簽、傳感器等領(lǐng)域展現(xiàn)出巨大的應(yīng)用前景。但是目前有機(jī)半導(dǎo)體材料的載流子遷移率普遍仍處于較低水平,還無(wú)法滿足微電子器件的要求。研究表明,有機(jī)半導(dǎo)體材料的分子取向?qū)Σ牧蟽?nèi)部的電荷傳輸起著決定性作用,不同器件對(duì)于分子取向的要求也不盡相同。分子取向取決于有機(jī)分子間相互作用力、有機(jī)分子與絕緣層間相互作用力二者之間的競(jìng)爭(zhēng)關(guān)系,是可以通過(guò)改變外界條件進(jìn)行調(diào)控的。因此,在原子水平上深入理解有機(jī)薄膜沉積生長(zhǎng)過(guò)程中分子取向影響機(jī)理及電荷傳輸特性,是提升有機(jī)半導(dǎo)體器件性能的核心問(wèn)題。本學(xué)位論文以典型的并五苯有機(jī)薄膜晶體管有源層的沉積制造為研究對(duì)象,通過(guò)仿真模擬-理論計(jì)算-實(shí)驗(yàn)驗(yàn)證相結(jié)合的方法,從分子間相互作用力的角度揭示了有機(jī)薄膜初始生長(zhǎng)過(guò)程中分子取向的形成和轉(zhuǎn)變機(jī)理,探討了工藝參數(shù)對(duì)分子取向的影響規(guī)律,對(duì)不同工藝參數(shù)下有機(jī)薄膜的電荷傳輸性質(zhì)進(jìn)行了理論預(yù)測(cè),給出了合理的工藝參數(shù)區(qū)間,并通過(guò)實(shí)驗(yàn)進(jìn)行了驗(yàn)證。論文主要研究工作和創(chuàng)新點(diǎn)包括：結(jié)合理論分析和分子動(dòng)力學(xué)模擬,研究了并五苯薄膜生長(zhǎng)過(guò)程中分子由平行取向轉(zhuǎn)變?yōu)橹绷⑷∠虻默F(xiàn)象,得到了取向轉(zhuǎn)變臨界分子數(shù),揭示了分子取向是由并五苯分子間相互作用能、并五苯分子與基底間相互作用能二者之間的強(qiáng)弱關(guān)系控制的,基底表面的改變可調(diào)控二者的強(qiáng)弱關(guān)系。基于分子動(dòng)力學(xué)方法系統(tǒng)地探討了基底溫度和外加電場(chǎng)對(duì)并五苯薄膜分子取向的影響規(guī)律,確定了最優(yōu)的基底溫度區(qū)間,以及合理的電場(chǎng)方向和強(qiáng)度。研究發(fā)現(xiàn),低溫時(shí)并五苯分子聚集形成具有直立取向、有序且熱穩(wěn)定的團(tuán)簇；高溫時(shí)并五苯分子將形成具有平行取向的無(wú)序團(tuán)簇。平行于并五苯分子長(zhǎng)軸或短軸的外加電場(chǎng)有助于分子直立在基底表面；垂直于并五苯分子平面的外加電場(chǎng)將使得分子平躺在基底表面。基于Marcus電荷傳輸理論,結(jié)合分子動(dòng)力學(xué)方法,密度泛函理論和動(dòng)態(tài)蒙特卡洛模擬研究了并五苯單晶和團(tuán)簇的電荷傳輸性質(zhì),通過(guò)計(jì)算不同基底溫度下并五苯薄膜載流子遷移率的變化趨勢(shì),得到了基底溫度的合理范圍。通過(guò)真空蒸鍍實(shí)驗(yàn),測(cè)試了不同基底溫度下制備的并五苯OTFT器件的載流子遷移率,建立了基底溫度與器件遷移率的關(guān)系,驗(yàn)證了仿真模擬和理論計(jì)算的結(jié)果。
[Abstract]:Organic thin film transistors have been widely used in flexible display, flexible storage, radio frequency identification (RFID) tags, due to their simple processing process and low manufacturing cost. Sensors and other fields show great application prospects. However, the carrier mobility of organic semiconductor materials is still at a low level, which can not meet the requirements of microelectronic devices. The results show that the molecular orientation of organic semiconductor materials plays a decisive role in the charge transport within the materials, and the requirements of molecular orientation are different for different devices. Molecular orientation depends on the interaction between organic molecules. The competitive relationship between organic molecules and insulating layers can be regulated by changing the external conditions. Therefore, understanding the mechanism of molecular orientation and charge transport during the deposition and growth of organic thin films at atomic level is the core problem in improving the performance of organic semiconductor devices. In this dissertation, the deposition of active layer of typical pentaben organic thin film transistors is studied. The method of simulation, theoretical calculation and experimental verification is used. The formation and transformation mechanism of molecular orientation during the initial growth of organic thin films are revealed from the point of view of intermolecular interaction forces. The influence of process parameters on molecular orientation is discussed. The charge transport properties of organic thin films under different process parameters are predicted theoretically and the reasonable range of process parameters is given and verified by experiments. The main research work and innovations are as follows: combining with theoretical analysis and molecular dynamics simulation, the phenomenon of molecular transformation from parallel orientation to vertical orientation during the growth process of penta-benzene thin film is studied, and the critical number of orientation transition molecules is obtained. It is revealed that the molecular orientation is controlled by the interaction energy between pentabenzene and the substrate, and the change of the substrate surface can regulate the strong or weak relationship between them. The effects of substrate temperature and applied electric field on molecular orientation of penta-benzene films were systematically discussed based on molecular dynamics method. The optimum substrate temperature range and the reasonable electric field direction and intensity were determined. It was found that clusters with vertical orientation, order and thermal stability were formed at low temperature and disordered clusters with parallel orientation at high temperature. The external electric field parallel to the long axis or short axis of pentabenzene helps the molecule to stand upright on the surface of the substrate, and the applied electric field perpendicular to the plane of pentabenzene will cause the molecule to lie flat on the surface of the substrate. Based on the Marcus charge transport theory, the density functional theory and the dynamic Monte Carlo simulation, the charge transport properties of penta-benzene single crystals and clusters were studied. The reasonable range of substrate temperature is obtained by calculating the trend of carrier mobility at different substrate temperatures. The carrier mobility of pentaben OTFT devices prepared at different substrate temperatures was measured by vacuum evaporation experiments. The relationship between substrate temperature and device mobility was established, and the results of simulation and theoretical calculation were verified.
【學(xué)位授予單位】：華中科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TN304;TN321.5

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