Advanced Electronic Materials Center, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
J Chem Phys. 2010 Jul 21;133(3):034706. doi: 10.1063/1.3456733.
We investigated the evolution of quaterrylene thin films on SiO(2) and on an octadecyltrichlorosilane self-assembled monolayer (OTS-SAM) to examine the impact of film strains on the growth processes and evolving structure. Surface modification by SAMs allowed tailoring of the growth process from a Stranski-Krastanov (SK) mode (layer-plus-island) on the SiO(2) surface to a Frank-van der Merwe mode (layer-by-layer) on the OTS surface. Detailed structural analysis by x-ray diffraction techniques confirmed that the SK mode was driven by lattice strain in the initial wetting layers on the SiO(2) surface. On the other hand, strain-free wetting layers were already formed at the beginning of growth on the OTS surface, thereby suppressing three-dimensional island formation. Moreover, the films on the SiO(2) surface were found to incorporate high microstrain induced by crystal defects such as dislocations and a mosaic structure. In contrast, few crystal defects were present in the films on OTS surface, demonstrating that OTS treatment enables marked improvement of the molecular alignment. These results clearly indicate that the lattice strain induced by the molecular-substrate interaction is essential for controlling the overall growth process.
我们研究了四元并苯在二氧化硅（SiO2）和十八烷基三氯硅烷自组装单层（OTS-SAM）上的薄膜演化，以考察薄膜应变对生长过程和演化结构的影响。通过 SAMs 进行表面修饰，可以将生长过程从 SiO2 表面的 Stranski-Krastanov（SK）模式（层加岛）调整为 OTS 表面的 Frank-van der Merwe 模式（层到层）。X 射线衍射技术的详细结构分析证实，SK 模式是由初始湿膜在 SiO2 表面的晶格应变驱动的。另一方面，在 OTS 表面的生长开始时已经形成了无应变的湿膜，从而抑制了三维岛的形成。此外，我们发现 SiO2 表面上的薄膜包含由晶体缺陷（如位错和镶嵌结构）引起的高微应变。相比之下，OTS 表面上的薄膜中存在的晶体缺陷很少，这表明 OTS 处理能够显著改善分子取向。这些结果清楚地表明，分子-衬底相互作用引起的晶格应变对于控制整体生长过程至关重要。
