有机半导体外延生长的扫描隧道显微镜研究

Scanning tunneling microscopy studies on the epitaxial growth of organic semiconductors

有机半导体薄膜的光、电等性质取决于有机分子的取向以及长程有序性.研究有机半导体的生长机理以及内在驱动力是一个重要环节.文章通过两个典型生长体系,perylene在Ru(0001)表面上的生长和tetracene在Ag(110)表面上生长过程的介绍,给出了形成有机半导体晶化薄膜的可能性以及决定其有序生长的内在驱动力.对于perylene在Ru(0001)表面上的生长,决定其过程的主要驱动力是分子间的相互排斥作用,在单分子层时,由于这种相互作用导致形成Ru(0001)-12×12-8 perylene有序超结构.而对于tetracene/Ag(110)体系,决定生长的驱动力主要表现为相互吸引作用,因此,在小于单分子层时,tetracene呈有序的岛状生长;而当tetracene膜的厚度大于单分子层时,呈逐层生长模式,并形成具有正交晶系结构的晶化薄膜.

The physical properties of organic films depend crucially on their orientations and long - range ordering. A thorough understanding of the growth mechanism of organic semconductors is of great importance. By studying the growth processes of two typical systems, perylene on Ru（0001 ） and tetracene on Ag（110）, the growth behavior of organic semiconductors and the possibility for formation of the organic crystalline films are addressed. For perylene on Ru（0001 ）, the results show a formation of the Ru（0001 ） - 12 × 12 - 8 perylene superstructure, and the growth behavior is mainly controlled by the laterally repulsive molecule - molecule interaction. However, in the case of tetracene on Ag（ 110）, the main driving force is the laterally attractive molecule - molecule interaction, so the tetracene grows in a 2D island mode in the monolayer regime but for thicker multilayers a crystalline film in a novel 3D orthorhombic structure is formed layer by layer.