Cross-linkable random copolymers as dielectrics for low-voltage organic field-effect transistors
Cross-linkable random copolymers as dielectrics for low-voltage organic field-effect transistors
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DOI：
10.1039/c5tc00352k
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发表时间：
2015-01-01
影响因子：
6.4
通讯作者：
von Seggern, H.
中科院分区：
文献类型：
--
作者：
Simas, E. Reis;Kang, E. S. H.;von Seggern, H.
已经报道了大量具有良好介电性能的交联聚合物;然而，它们都具有缺点，如不受控制的预交联、需要高加工温度以及需要额外的交联化合物。在这方面的贡献，两个新的聚（甲基丙烯酸甲酯）的聚合物，可以交联由于连接的苄基叠氮（N-3）单体单元，使另外的硬化剂或引发剂过时。的共聚物的合成以及它们的成功的表征和使用作为栅极的有机场效应晶体管的证明。所研究的聚合物已根据其叠氮化物含量（以摩尔%计）标记为PAZ 12和PAZ 14。对于PAZ 12，聚合物的附加结构单元是甲基丙烯酸甲酯，对于PAZ 14，甲基丙烯酸甲酯和苯乙烯单体单元以约相等的比例存在。旋涂薄膜通过在110 ° C下热处理，随后在254 nm波长下UV暴露而交联，产生不溶性、光滑且电致密的聚合物网络。采用红外光谱法跟踪N-3振动模式，获得了最佳交联参数。它的消失证实了完全的交联反应，因此完全反应的叠氮基有利于分析。用阻抗谱研究了交联薄膜的介电性能。双层双金属化的应用在随后生产的并五苯基场效应晶体管中导致较低的介电损耗和较低的漏电流。这些器件在低于-6 V的电压下工作，表现出无滞后的电流-电压特性，空穴迁移率高达0.16 cm（2）V-1 s（-1）。PAZ 12似乎比PAZ 14更上级，这是由于低至92 nm的较低的总层厚度仍然在晶体管中提供良好的绝缘，这可能与在含双组分共聚物PAZ 12的交联网络中产生的较低自由体积有关。
A large number of cross-linkable dielectrics with good dielectric properties have been reported; however, all of them suffer from disadvantages like uncontrolled pre-crosslinking, necessity of high process temperatures and the need for an additional cross-linking compound. In this contribution, two new poly(methyl methacrylate) polymers are introduced which can be cross-linked due to the attached benzyl azide (N-3) monomer units making the addition of hardeners or initiators obsolete. The synthesis of the copolymers as well as their successful characterization and usage as gate dielectrics for organic field-effect transistors is demonstrated. The investigated polymers have been labeled PAZ 12 and PAZ 14 according to their azide content in mol%. The additional building blocks of the polymers are methyl methacrylate for PAZ 12 and methyl methacrylate and styrene monomer units in about an equal ratio for PAZ 14. Spin-coated thin films were cross-linked by a thermal treatment at 110 degrees C followed by an UV exposure at a wavelength of 254 nm yielding insoluble, smooth and electrically dense polymeric networks. Optimal cross-linking parameters were obtained using infrared spectroscopy to follow the N-3 vibrational mode. Its disappearance confirms a complete cross-linking reaction, and thus fully reacted azide groups facilitate the analytics. The dielectric properties of the cross-linked thin films have been studied by impedance spectroscopy. The application of double layer dielectrics results in lower dielectric losses and lower leakage currents in the subsequently produced pentacene-based field-effect transistors. These devices operate at voltages below -6 V and show hysteresis-free current-voltage characteristics with hole mobilities up to 0.16 cm(2) V-1 s(-1). PAZ 12 appears to be superior to PAZ 14 due to a lower total layer thickness of down to 92 nm still providing good insulation in the transistor presumably related to a lower free volume that arises in the cross-linked network of the two-component containing copolymer PAZ 12.