有机薄膜异质结外延界面的构筑及薄膜晶体管性能的研究

The remarkable progress of organic semiconductor has recently been obtained and hole field effect mobility has been up to 40 cm2/Vs as measured from single crystal transistors, indicating a bright future for numerous electronic applications. However, it has been found difficult to form high-mobility thin films in view of their use as semiconductor layers in high integrated organic devices because of the poor crystallinity and the presence of disorder. Heteroexpitaxy is of great potential in controlling molecular ordering of organic semiconductors and fabricating highly ordered and aligned structures for organic thin films. . In this project, highly ordered and crystalline organic thin film heterostructures were grown on silicon nitride insulating substrates by organic epitaxy, which was combined with a novel off-centre spin-coating and double-material spin-coating method for controlling formation of molecular flat surfaces. And the fine-tuned morphology and epitaxial interface will be constructed to achieve high-quality organic thin film transistors (OTFTs) having few defects and grain boundaries. Firstly, the surface of silicon nitride insulator will be treated with organic molecules as modification layer in order to form micron-sized crystallites and relatively flat surface. Secondly, the highly oriented and crystalline thin films will be fabricated as template layer by vacuum vapor evaporation for the epitaxial interface. The symmetry and corrugation of organic template layer will be studied to induce the crystallization of the active layer. And the organic active layer will be deposited on the template layer, taking advantage of organic epitaxy. A detailed analysis of the heteroepitaxial interface in terms of adhesion energy, molecular arrangement, degree of crystallinity and order of the active layer will be presented. The epitaxial relationship between organic semiconductor overlayer and the layer underneath the driving forced leads to organic epitaxy. The microscopic approach based on force-field calculation of the interfacial energy gives insights into the mechanisms and the requisites for obtaining crystalline on the template layer and the growth mode in other epitaxial systems.. Furthermore, the project will investigate the preparation methods of epitaxial interfaces manipulation in organic thin film heterostructures and the comprehensive properties, explore the thin film microstructure and interfacial properties for high-performance OTFTs, compare the influence of the various template layer on epitaxial interfacial properties, clarify the effect of the template layer on electronic properties and reliability of OTFTs, and establish the relationship between structure and properties. Therefore, this project will favor to prepare excellent organic thin film transistors and provide theoretical fundament for the further application and development of organic electronics.

有机半导体近年取得显著进展，单晶迁移率超过40 cm2/Vs。但形成有机薄膜时结晶性差、迁移率低，难以应用到高集成薄膜晶体管中。异质外延是构筑有序排列、均匀、稳定有机薄膜有效手段。本课题将以有机异质外延，结合特殊旋涂技术，在氮化硅绝缘层上构筑高有序、高结晶外延界面，解决高单晶迁移率和低薄膜结晶性的矛盾，实现高性能有机薄膜晶体管。首先采用偏心旋涂及两种材料同时旋涂技术，在氮化硅表面上实现微晶尺寸、相对平整修饰层。其次真空气相沉积有机诱导层，调整蒸镀速率、衬底温度，控制分子排列及流动行为，研究改善薄膜结晶性、均匀性方法及原理。然后，外延生长有机薄膜，调控结晶度和薄膜微结构，构筑多晶形态外延界面。最后探索薄膜微结构与界面性能、电性能和稳定性的关系，获得高性能有机薄膜晶体管。对比研究修饰层、诱导层对外延界面性能的影响，建立结构与性能关系模型，研究载流子传输机制，为有机薄膜晶体管的应用提供科学依据。

有机薄膜是众多有机半导体器件的基础，近年发展迅速。有机薄膜的结晶性差、有序度低，难以应用到高集成有机半导体器件中。异质外延是构筑有序排列、均匀的有机薄膜的有效手段，但有机薄膜的生长过程及调控机制仍不清晰。本项目通过有机异质外延及旋涂技术，在绝缘层上构筑高有序、高结晶的外延界面，调控有机分子排列及流动行为，研究外延界面层和有机半导体层的生长关系，获得薄膜微结构与性能的关系模型，为有机薄膜的生长提供实验依据和理论指导。基于外延界面诱导生长的方法获得了高响应度和低回复时间的有机薄膜晶体管气体传感器。本项目按照研究计划执行，完成任务书中全部研究计划和目标。取得的主要成果如下：.1) 采用四噻吩为诱导层，利用蒸镀方法，调控蒸镀速率、衬底温度，研究四噻吩诱导层的形貌性能和晶体结构，对比研究六联苯诱导层，获得高有序、结晶性的诱导层薄膜，提供了构筑有机薄膜异质结外延界面的制备方法。.2) 采用异质诱导层上外延生长方法，研究不同诱导层上红荧烯薄膜的表面形貌和晶体结构，与直接生长在绝缘层上的红荧烯薄膜对比，在诱导层上获得高有序、多晶结构的红荧烯薄膜，建立诱导生长的薄膜表面形貌与界面性能的关系模型。.3) 采用旋涂方法制备绝缘层的聚合物修饰层，调控聚合物层的溶液浓度和双层薄膜的退火温度，获得高结晶性的红荧烯薄膜，建立聚合物修饰层上红荧烯晶体的生长机制模型。.4) 采用双异质诱导层制备红荧烯薄膜，研究衬底温度对红荧烯薄膜形貌的影响。研究不同生长速率的诱导层对有机薄膜晶体管的气体传感器性能的影响，获得了高响应度和低回复时间的NO2传感器，为有机薄膜晶体管的应用提供科学依据。.在本项目的资助下，在国内外重要期刊共发表学术论文12篇，其中SCI论文5篇，EI论文4篇，中文核心期刊论文3篇。已授权发明专利6项，申请中的发明专利6项。培养硕士研究生11名。圆满地完成了项目书中的预期研究成果。