發(fā)布時間：2018-04-30 11:45

  本文選題：有機薄膜晶體管 + 氣體傳感器��； 參考：《電子科技大學》2016年博士論文

【摘要】：有機薄膜晶體管(Organic Thin film transistor,OTFT)由于其制備成本低、易實現(xiàn)大面積、制備方法簡單和可彎折等特點在未來具有廣闊的應用前景。目前,OTFT器件在有機發(fā)光二極管顯示、射頻識別、傳感器等領域顯示了重要的應用價值。尤其是在氣體傳感器方面,多參數(shù)模式、易集成和可彎折等優(yōu)點成為其他類型氣體傳感器所不能取代的優(yōu)勢。OTFT氣體傳感器最大的特點在于有源層薄膜是OTFT器件的導電溝道層也是氣體傳感器的氣體敏感薄膜。因此。針對OTFT有源層薄膜的選擇、修飾、改性一直是人們提高OTFT氣體傳感器性能所關注的焦點。根據(jù)不同類型的OTFT器件的特點,本文采用底柵底接觸結構的OTFT器件,以便氣體敏感薄膜能夠與待測氣體分子直接接觸,提高OTFT氣體傳感器的性能。制備了以聚(三-己基噻吩)(Poly(3-hexylthiophene),P3HT)、P3HT-氧化鋅(Zinc Oxide,ZnO)納米棒的復合薄膜、P3HT/還原的氧化石墨烯(Reduced Graphene Oxide,RGO)分層薄膜等作為敏感薄膜的OTFT氣體傳感器,對其器件的基本電學性能和氣敏性能進行了系統(tǒng)的分析和研究。同時,結合多種分析手段對氣敏薄膜的特性進行表征,深入地探討了氣體傳感器的氣敏機理。論文的主要研究內容包括以下幾個方面:1.制備了基于P3HT薄膜的OTFT氣體傳感器用于檢測二氧化氮(nitrogen dioxide,NO2)。研究了氣體傳感器的敏感機理,得到了氣敏薄膜的最佳優(yōu)化參數(shù)。實驗結果表明適當?shù)臏p小器件中敏感薄膜的厚度有利于傳感器性能的提高。敏感薄膜采用噴涂成膜的方式制備,通過控制噴涂溶液的體積沉積不同厚度的敏感薄膜。首先,針對P3HT薄膜研究了其對NO2的氣體敏感機理。由于柵極電壓能夠調控器件中載流子的分布狀態(tài),對柵極施加不同的電壓條件,驗證氣體傳感器的主要響應機制為類似“摻雜效應”。然后,改變敏感薄膜厚度優(yōu)化OTFT氣體傳感器的性能。對比不同厚度薄膜器件之間的差異發(fā)現(xiàn):(1)薄膜的厚度增加導致界面處的表面勢變大,這樣就會在相同的柵極電壓下吸附更多的空穴載流子形成導電通道,因此OTFT的閾值電壓會向正值方向移動,遷移率增大。(2)隨著敏感薄膜厚度的減小,傳感器對相同濃度NO2的響應值會變大。這是因為在厚度較小的薄膜中,空氣/P3HT界面與P3HT/SiO2界面相鄰較近,表面吸附的氣體分子會以相對更大程度地擾亂溝道中的空穴載流子傳輸。2.將Zn O納米棒摻雜引入到P3HT薄膜中用來優(yōu)化OTFT氣體傳感器的性能,并結合對傳感器敏感機理的研究,提出了兩種快速、準確評估OTFT氣體傳感器性能的方法,用來解決傳感器恢復時間過長造成的響應偏差。文中詳細地研究了zno納米棒的摻雜對p3ht薄膜的微觀結構的影響。zno納米棒促進了p3ht薄膜的結晶度增加和p3ht側鏈的取向更加規(guī)則,這就會引起器件內載流子運輸狀態(tài)的變化,優(yōu)化了器件的電學性能。此外,p3ht與zno納米棒構成了異質結結構導致薄膜中電子與空穴的分布產生變化,改善了器件的性能。室溫下測試otft器件對no2的氣敏性能,結果表明:otft氣體傳感器對no2十分敏感,最低檢測限達到幾ppb。但是在測試高濃度的no2時,存在傳感器恢復時間過長的這一問題,影響otft氣體傳感器的準確性。為了克服這個問題,提出了兩種能夠快速、準確地評估傳感器性能的方法。第一種方法是采用otft器件的閾值電壓變化作為傳感器的輸出信號。多次針對沒有完全恢復的器件測試發(fā)現(xiàn)在同一濃度的待測氣體下,傳感器閾值電壓的變化基本相同。第二種方法是基于氣體分子的吸附行為方程提出的一種數(shù)據(jù)處理方法。經過試驗數(shù)據(jù)的驗證這種方法具有很高的可靠性。3.率先將二硫化鉬(molybdenumdisulfide,mos2)引入到聚合物p3ht中作為nh3傳感器的敏感材料,制備不同結構的敏感薄膜,發(fā)現(xiàn)采用p3ht-mos2復合薄膜的傳感器的恢復時間明顯縮短。mos2是一種典型的二維半導體材料,其特點是載流子遷移率高。制備的器件由于mos2的存在otft器件的電學性能發(fā)生了明顯的改變,其中otft的輸出特性曲線中的飽和區(qū)不再明顯。研究了制備的薄膜微觀結構的差異發(fā)現(xiàn):mos2的加入使得p3ht分子與分子之間的距離由于相互作用的原因變小了。這就會使載流子在有源層溝道內的傳輸更為迅速。因此,氣體傳感器表現(xiàn)出更好的恢復性。而分層膜結構的改善沒有復合膜結構的明顯。此外,還深入地討論了氣體響應的敏感機理,采用不同載氣對傳感器的性能進行測試。結果表明:氧氣分子在沒有進行氣體測試之前已經預先占據(jù)了強弱的吸附位,當接觸到氨氣分子之后,氨氣分子與氧氣分子競爭奪取氣體的吸附位。氣體的恢復過程是其相反的過程。4.將新型氣敏材料rgo與聚合物p3ht制備成p3ht/rgo分層薄膜結構的敏感薄膜,發(fā)現(xiàn)rgo作為底層材料可以提高對no2氣體的靈敏度,改善rgo薄膜對氣體的選擇性。文中對制備的器件電學性能測試得到:因為rgo材料的電導率和遷移率都很高,所以otft輸出特性曲線沒有發(fā)現(xiàn)明顯的飽和區(qū),這嚴重地影響了otft的電學性能。但是對于no2氣敏性能測試結果得到:采用rgo作為底層,p3ht作為頂層的這種分層薄膜結構明顯提高了no2氣體傳感器的響應和靈敏度。這與rgo本身的二維納米結構有關,待檢測氣體分子能夠直接與材料的全部原子接觸。深入地研究待測氣體的實時響應-恢復曲線發(fā)現(xiàn)rgo在與no2氣體分子吸附時存在著不同的吸附位,響應曲線中存在快慢響應之分。此外,P3HT作為頂層材料對底層RGO材料有一個修飾的作用,阻止了其他氣體與底層的RGO接觸,提高了基于RGO氣體傳感器的選擇性。
[Abstract]:Organic Thin film transistor (OTFT) has a wide application prospect in the future because of its low preparation cost, easy realization of large area, simple preparation method and bending and so on. At present, OTFT devices have shown important application value in the fields of organic light emitting diode display, radio frequency identification, sensor and so on. As for the gas sensor, the advantages of multi parameter mode, easy integration and bending are the most important features of.OTFT gas sensors which can not be replaced by other types of gas sensors. The active layer film is the conductive channel layer of the OTFT device and the gas sensitive thin film of the gas sensor. Therefore, the choice of the OTFT active layer film is the choice of the active layer film. Modification, modification has always been the focus of people to improve the performance of OTFT gas sensors. According to the characteristics of different types of OTFT devices, this paper uses the OTFT device with the bottom contact structure so that the gas sensitive film can directly contact with the gas molecules to be measured and improve the performance of the OTFT gas sensor. The poly (three - hexyl thiophene) is prepared. Poly (3-hexylthiophene), P3HT), P3HT- Zinc Oxide (Zinc Oxide, ZnO) nanorod composite film, P3HT/ reduced graphene oxide (Reduced Graphene Oxide, RGO) layered film, etc. as sensitive gas sensors, the basic electrical properties and gas sensing properties of the devices are systematically analyzed and studied. The characteristics of gas sensitive film are characterized by means of analysis, and the gas sensing mechanism of gas sensor is deeply discussed. The main contents of this paper are as follows: 1. the OTFT gas sensor based on P3HT film is prepared to detect nitrogen dioxide (nitrogen dioxide, NO2). The sensitive mechanism of gas sensor is studied, and gas is obtained. The optimum parameters of the sensitive thin film are obtained. The experimental results show that the appropriate thickness of the sensitive thin film in the device is beneficial to the performance of the sensor. The sensitive thin film is prepared by spraying film, and the sensitive film of different thickness is deposited by controlling the volume of the spray solution. First, the needle is studied for the gas sensitivity of the P3HT film to the NO2. The mechanism. Because the grid voltage can regulate the distribution of the carrier in the device and apply different voltage conditions to the gate, it is proved that the main response mechanism of the gas sensor is similar to the "doping effect". Then, the performance of the OTFT gas sensor is optimized by changing the thickness of the sensitive film. The difference between the thin film devices with different thickness is found: (1) The increase of the thickness of the film leads to the larger surface potential at the interface, so that more cavity carriers will be adsorbed at the same gate voltage to form a conductive channel. Therefore, the threshold voltage of OTFT will move towards the positive direction and the mobility increases. (2) the response value of the sensor to the same concentration of NO2 will become larger as the thickness of the sensitive film decreases. It is because in the thin films that the air /P3HT interface is adjacent to the P3HT/SiO2 interface, and the adsorbed gas molecules will disrupt the hole carrier in the channel to a relatively large extent.2., and the Zn O nanorod doping is introduced into the P3HT film to optimize the performance of the OTFT sensor and the sensitive mechanism of the sensor is combined with the sensor. Two rapid and accurate methods for evaluating the performance of OTFT gas sensors are proposed to solve the response deviation of the sensor with long recovery time. The effect of the doping of ZnO nanorods on the microstructure of the P3HT thin film is studied in detail. The.Zno nanorods promote the increase of the crystallinity of the P3HT film and the orientation of the P3HT side chain more. With the addition of rules, this will cause the change of carrier transport state in the device and optimize the electrical performance of the device. In addition, P3HT and ZnO nanorods constitute a heterostructure that leads to the change in the distribution of electrons and holes in the film, and improves the performance of the device. At room temperature, the gas sensing performance of the OTFT device to the NO2 is tested. The results show that OTFT gas sensing is used. The device is very sensitive to NO2, and the minimum detection limit reaches a few ppb., but when testing the high concentration of NO2, there is a problem that has a long recovery time of the sensor, which affects the accuracy of the OTFT gas sensor. In order to overcome this problem, two methods that can quickly and accurately evaluate the performance of the sensor are proposed. The first method is to use the OTFT device. The threshold voltage variation is used as the output signal of the sensor. Many times for the device test which is not fully recovered, the change of the threshold voltage of the sensor is basically the same under the same concentration of gas. The second method is a data processing method based on the adsorption behavior equation of gas molecules. This method has a high reliability.3. first to introduce molybdenumdisulfide (MoS2) into the polymer P3HT as a sensitive material for NH3 sensor, and to prepare sensitive thin films with different structures. It is found that the recovery time of the sensor using p3ht-mos2 composite thin film can obviously shorten the.Mos2 is a typical two-dimensional semiconductor material. The characteristic is the high mobility of the carrier. The electrical performance of the OTFT device is obviously changed because of the existence of MoS2. The saturation zone in the output characteristic curve of the OTFT is no longer obvious. The difference of the microstructure of the prepared thin film is studied. It is found that the addition of MoS2 makes the distance between the P3HT molecules and the molecules due to the interaction. This causes the carrier to transmit more rapidly in the active layer channel. Therefore, the gas sensor shows better recovery. The improvement of the layer membrane structure is not obvious in the composite membrane structure. In addition, the sensitive mechanism of the gas response is discussed deeply, and the performance of the sensor is tested with different carrier gas. The results show that the oxygen molecules have pre occupied the strong and weak adsorption sites before the gas test. When the ammonia molecules are exposed to the ammonia molecules, the ammonia molecules compete with the oxygen molecules to capture the adsorption position of the gas. The recovery process of the gas is the reverse process.4. to prepare the new gas sensitive material RGO and the polymer P3HT into p3ht/rgo stratification. The sensitive film of the membrane structure found that RGO as the underlying material could improve the sensitivity of the NO2 gas and improve the selectivity of the RGO film to the gas. In this paper, the electrical properties of the fabricated devices were tested because the conductivity and mobility of the RGO materials were very high, so the OTFT output characteristic curve did not find the obvious saturation area, which was seriously affected. The electrical performance of OTFT was rounded. But the results of NO2 gas sensitivity test were obtained: using RGO as the bottom layer, the layered thin film structure of P3HT as the top layer obviously improved the response and sensitivity of the NO2 gas sensor. This is related to the two-dimensional nanostructure of the RGO itself, and the gas molecules can be directly contacted with all the atoms of the material to be detected. The real-time response recovery curve of the gas to be measured has been deeply studied. It is found that RGO has different adsorption sites when adsorbing NO2 gas molecules, and there is a quick and slow response in the response curve. In addition, P3HT as a top layer material has a modified effect on the underlying RGO material, which prevents other gases from contacting RGO at the bottom and improves the RGO based gas. The selectivity of the body sensor.

【學位授予單位】：電子科技大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TN321.5

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本文編號：1824428