【作者】 李娴；

【导师】 蒋亚东；

【作者基本信息】 电子科技大学 ， 光学工程， 2013， 博士

【摘要】 有机薄膜晶体管（Organic Thin-Film Transistors, OTFT）气体传感器是近年来国际上化学传感领域发展较为迅速的一种新型气体传感器，相较于传统气体传感器具有很多独特的优势，如尺寸小、成本低、制备工艺简单、多参数检测、便于集成等。本文以薄膜晶体管为传感器件，在对器件制备工艺和结构参数进行优化的基础上，对OTFT电学特性和OTFT气体传感器的气敏特性进行了系统的研究，同时对其气敏机理进行了深入的分析研究。其主要内容包括以下几个方面：1.以n型重掺杂硅外延片作为衬底，热氧化二氧化硅（SiO₂）作为绝缘层，具有叉指电极结构的钛/金电极作为源极和漏极制备了薄膜晶体管器件。设计了不同的绝缘层厚度（125nm、195nm和300nm）和不同沟道宽长比（40、160和640），采用真空蒸发镀膜工艺分别在在薄膜晶体管上制备了酞菁铜（CopperPhthalocyanine, CuPc）和α-六噻吩（α-Sexithiophene，α-6T）作为有机有源层，首次研究了绝缘层厚度对于OTFT气敏性能的影响，同时对沟道宽长比的影响也进行了测试分析。测试结果表明，当绝缘层厚度为125nm、沟道宽长比为160时，OTFT气体传感器表现出最优的电学和气敏特性，利用OTFT的载流子传输理论对测试结果进行了分析。2.对金属酞菁薄膜晶体管的气敏特性和敏感机理进行了系统研究。研究了CuPc薄膜晶体管气体传感器对H2S气体的气敏性能，该传感器在室温下对H2S表现出较好的响应/恢复特性、重复性和选择性。实验过程中分析发现，空气中的氧对于有机薄膜晶体管气体传感器的性能具有重要作用，气体分子的极性和得失电子能力的强弱直接影响器件对气体响应的大小。同时对基于p型的CuPc、酞菁钴（Cobalt Phthalocyanine， CoPc）和n型十六氟酞菁铜(CopperHexadecafluorophthalocyanine，F₁₆CuPc)OTFT的电学特性和对甲基磷酸二甲酯（Dimethyl methylphosphonate，DMMP）的气敏响应进行了测试；测试结果表明，CoPc和F₁₆CuPcOTFT均具有良好的电学性能，但对相同浓度的DMMP响应均低于CuPcOTFT，这是因为CuPc薄膜中的Cu离子对DMMP具有一定的催化降解作用，从而对DMMP表现出较好的响应。3.在薄膜晶体管上采用气喷镀膜工艺制备了聚（3-己基噻吩）（Poly（3-hexylthiophene），P3HT）/氧化锌（ZnO）纳米颗粒有机/无机复合薄膜，研究了该传感器在室温下对甲醛（Formaldehyde，HCHO）气体的响应特性；结果表明，P3HT/ZnO复合薄膜晶体管相比于P3HT薄膜晶体管对甲醛表现出更大的响应和恢复特性，这是因为P3HT/ZnO复合薄膜的多孔三维网状结构为甲醛气体分子提供了更多的吸附位，从而有利于甲醛的吸附和解析，同时n型ZnO与p型P3HT在接触界面形成了pn异质结，其界面累积的载流子能有效弥补半导体薄膜中的缺陷，从而有助于电子/空穴的传输，在一定程度上提高了器件的性能。不同气喷量和复合薄膜中ZnO纳米材料的含量对复合薄膜的形貌及气敏性能有一定影响；优化后的P3HT/ZnO复合薄膜OTFT对甲醛气体表现出良好的响应/恢复特性、重复性和选择性，但稳定性能有待进一步提高。此外，对比分析了P3HT/ZnO、P3HT/Fe₂O₃和P3HT/InSnO复合薄膜晶体管对甲醛的气敏特性，实验结果表明，P3HT/ZnO薄膜晶体管具有最优的气敏性能，结合纳米材料的尺寸和能带宽度、器件的电学特性对测试结果进行了深入的分析。4.对基于P3HT-ZnO异质结结构分层薄膜和P3HT/ZnO复合薄膜的薄膜晶体管的气敏性能进行了对比，结果表明P3HT/ZnO复合薄膜晶体管在室温下对NO₂气体的气敏性能明显优于P3HT-ZnO异质结器件，结合薄膜形貌和载流子传输机理进行了分析。F₁₆CuPc-CuPc异质结薄膜晶体管对NO₂气体具有一定的响应，但并未表现出恢复特性，其性能有待进一步的深入研究。更多还原

【Abstract】 Organic Thin Film Transistors （OTFT） gas sensor is a novel and fast developinggas sensor device at the field of international chemical sesors in recent years. OTFT gassensor has many distinctive advantages compared with other traditional gas sensors,such as small size, low cost, simple fabricated technology, multi-parameter detection,easy integration. This dissertation adopted OTFT as sensing component, and carried outa series of research at the electrical characteristics of OTFT and sensing properties ofOTFT gas sensor on the basis of the fabrication technology and parameter optimizationof the device. The main content includes following points:1. Thin-Film Transistors were made in a bottom contact configuration on aSb-doped n+-type Czochralski （CZ）-grown silicon wafer. The gate dielectric layer wasthermal SiO₂. The source and drain interdigital electrodes were formed by depositingtitanium （Ti） film （20nm） and gold （Au） film （50nm） on the top of the gate dielectric.During the fabrication process of TFT, different thickness of the insulator layer （125nm,195nm and300nm） and different ratios of channel width to length （40,160and640）were designed. Copper Pthalocyanine （CuPc） and α-Sexithiophene （α-6T） weredeposited onto the electrode layer and used as the organic active layer by vacummevaporation. CuPc TFTs were used to investigate the dependence of electricalcharacteristics and sening properties to H2S gas on the thickness of the insulator layer atroom temperature. α-6T TFTs were used to investigate the dependence of electricalcharacteristics and sening properties to NO₂gas on the channel parameters at roomtemperature. The results showed that the TFTs with195nm thick-insulator layer and160ratio of channel width to length exhibite the optimal electrical characteristics andsening properties. Carrier transport theory of OTFT was used to understand themechanism of this process and results.2. The gas-sensing properties and sensing mechanism of TFT based metalpthalocyanines were investigated systematically. The TFT based CuPc （p type）semiconductor film was fabricated to study its sensing properties to H2S. The resultsshowed that CuPc TFT exhibited good response/recovery, repeatability and selectivity at room temperature. It was found that oxygen in air played important roles in theproperties of OTFT gas sensor combing with surface morphology of CuPc film. Thepolarities and abilities of donating or trapping electrons of gas molecur influenced thesensing response of OTFT gas sensor directly. At the same time, CuPc, CobaltPhthalocyanine （CoPc, p type） and Copper Hexadecafluorophthalocyanine (F₁₆CuPc, ntype) were fabricated on TFTs to study their electrical characteristics and seningproperties to nerve agent simulants-dimethyl methylphosphonate （DMMP）. The resultsshowed that the CoPc and F₁₆CuPc TFTs exbihited good electrical characteristics, butshowed weaker response to DMMP with same concentration compared with CuPc TFT.The Cu ion in CuPc may be helpful to the catalysis and degradation of DMMP andCuPc TFT exhibited better respone.3. Poly （3-hexylthiophene）（P3HT） composite materials were fabricated on TFTs asactive layer by spray-deposited method. The sening properties to formaldehyde （HCHO）of P3HT/ZnO composite TFTs were investigated. The results showed that P3HT/ZnOcomposite TFT exhibited better response and recovery to HCHO compared with P3HTTFT. The surface morphology revealed that the P3HT/ZnO composite film exhibitedthree-dimensional network structure and existed many holes, which provided adsorptionsites and helped to the adsorption and desorption of HCHO gas molecules. The interfaceof n type ZnO and p type P3HT formed p-n heterojunction. The carriers accumulated atthe interfaces could make up the defects of semiconductor film effectively and benefitedthe transport process of electrons or holes, which improved the electrical and sensingcharacteristies to some extent. It was found that the different airbrush mass （thethickness of film） and the ratio of ZnO in P3HT/ZnO composite had dependence onmorphology of the film and the properties of OTFT gas sensor. The optimizedP3HT/ZnO composite film TFT exhibited good response/recovery, repeatability andselectivity at room temperature, but the stability needed further improvements.Moreover, P3HT/iron oxide （Fe₂O₃） and P3HT/indium oxide/tin oxide （simpled asInSnO） TFTs were fabricated with the same technology and compared with P3HT/ZnOTFTs. The results showed that P3HT/ZnO TFTs exhibited optimum electrical andHCHO-sensing properties. The size and energy band of nano-materials and theelectrical properties were adapted to analyze the experiment results.4. The gas sensing properties of P3HT-ZnO heretolunction TFTs and P3HT/ZnO composite film TFTs were compared and analyzed. The results showed these twodevices had good electrical characteristics. But P3HT-ZnO heretolunction TFTsexhibited weaker response to NO₂than P3HT/ZnO composite TFTs at room temperature.The morphology of film and carrier transport theory were considered to analyze thereason. F₁₆CuPc-CuPc heretolunction TFTs showed some response and no recovery toNO₂at room temperature. The properties of F₁₆CuPc-CuPc heretolunction TFTs neededfurther researches.更多还原