Self-Organized Growth of Organic Thiophene-Phenylene Nanowires on Silicate Surfaces

摘要

Results of a systematic study of the growth of blue-green light-emitting 2,5-di-4-biphenyl-thiophene (PPTPP) molecules on the (001) faces of the sheet silicates muscovite and phlogopite mica are reported. This includes morphology, crystallography, and optical properties. It is shown that small changes in the choice of the substrate lead to distinctly different growth behavior. On muscovite, a commensurate wetting layer of lying molecules is initially formed with subsequent formation of clusters, which assemble into mutually parallel nanowires. The wires grow along a muscovite direction, having the molecules oriented perpendicular to the wire direction and parallel to the surface plane. On phlogopite mica, no wetting layer is observed, but diffraction from islands of upright molecules, forming a coincidence lattice. Fibers grow along three different directions, until they start bending. In comparison to similar organic molecules, it is found that overall PPTPP has a growth behavior more similar to that of the p-phenylenes as compared to that of the α-thiophenes.