利用界面调控制备二维有机半导体晶体及其机制研究

二维有机半导体晶体是利用分子间的范德瓦耳斯力进行自组装生长的单晶材料。本质上的单晶属性使其具备优异的电学特性。更重要的是,二维极限下增强的界面特性能够大幅调控器件行为,为构建多功能界面器件提供可能。此外,充分暴露的电荷输运沟道和极少的晶面内缺陷能够为研究本征的有机电子输运特性创造可能。目前,对于二维有机半导体晶体的生长工艺研究已经取得了较大的进展,但是从理论层面上研究二维晶体生长的自组装过程仍然十分匮乏。本工作利用添加剂辅助结晶技术成功制备出二维有机半导体晶体,并通过偏光显微镜和原子力显微镜对二维晶体进行了全面的表面形貌和结构表征。通过SEM结合EDS技术对关键的形核界面进行了结构和组成的表征以研究晶体生长的机制。研究结果表明:在添加剂界面上,生长材料能够稳定形核,并计算出添加剂构建的有利界面能够将形核势垒降低为SiO₂界面上的1/5。这项工作充分展现了生长界面对于晶体生长的关键作用,并从理论上揭示了界面的调控行为,为二维有机半导体晶体的生长工艺设计提供了可靠的思路。

Preparation and Mechanism of 2D Organic Semiconductor Crystals by Interface Control

Two-dimensional (2D) organic semiconductor crystals are single crystal materials grown by self-assembly using intermolecular van der Waals forces. The intrinsically single crystal properties make it possess excellent electrical properties. More importantly, the enhanced interfacial properties in the 2D limit can greatly tune the device behaviors, providing the possibility to construct multifunctional interfacial devices. In addition, the exposed charge transport channel and few in-plane defects make it possible to study the intrinsic transport properties of organic electrons. At present, great progress has been made in the growth process of two-dimensional organic semiconductor crystals, however, the theoretical study of the self-assembly process of two-dimensional crystal growth is still very scarce. In this work, two-dimensional organic semiconductor crystals were successfully prepared by additive-assisted crystallization technology, the surface morphology and structure of the two-dimensional crystals were comprehensively characterized by polarized light microscopy and atomic force microscopy. For the mechanistic study of crystal growth, the SEM combined with EDS techniques were employed to study structural and compositional characterization of key nucleation interfaces. The results show that the growth material can nucleate stably at the additive interface, and it is calculated that the favorable interface constructed by the additive can reduce the nucleation barrier to 1/5 of that on the SiO₂ interface. This work fully demonstrates the key role of the growth interface in crystal growth, and theoretically reveals the regulated behavior of the interface, that provides a reliable idea for the growth process design of two-dimensional organic semiconductor crystals.