| The opto/electronic properties and solid-state structures of fluoro-substituted conjugated organic systems exhibit unique characteristics in comparison with their counterparts. The film forming, structural evolution and the consequences to their opto/electronic properties are of crucial importance to the smart devices based on organic hetero-structures. In this thesis, three fluoro-substituted compounds, zinc hexadecanfluoro-phthalocyanine (ZnF16Pc), N,N'-(4-trifluoromethyl-2,3,5,6-tetra- fluorophenyl)-3,4,9,10-tetracarboxylicperylenediimide (F-PTCDI) and tetrakis- (meso-2,3,4,5,6-pentafiuorophenyl)-zinc porphyrin (ZnFTPP), were synthesized and purified. Elementary analyses, FTIR, 1H-NMR and UV-visible spectroscopy were used to characterize their chemical structures. The UV-visible spectroscopy, atomic force microscopy(AFM), X-ray diffraction(XRD), scanning electron microscopy (STM), polarized optical microscopy were applied to investigate the growth mechanisms and molecular architectures of these planar conjugated molecules.ZnF16Pc molecules grow on quartz substrate in a Stransky-Krastanov model; a fundamental layer is laid by strong interactions between quartz and F-atoms on ZnF16Pc, on which an amorphous transition layer develops, finally an well ordered film is obtained, "card-packing", "amorphous accumulation" and "brick-stacking" are adopted hi three different layers. In the "card-packing", a ZnF16Pc molecule takes an angle of 52 respect to the substrate. While in the "brick-stacking", the molecules arrange in a square lattice with lattice constant as 14.94A and 14.28A under room temperature and 300℃ respectively.From room temperature to about 150℃, F-PTCDI molecules follow the Vollmer- Weber rule when grown on quartz substrate, as revealed by AFM images. Also shown by AFM images are the regular features of crystals and ordered crystal domains for the film grown on 200 ℃ substrates, the morphologies indicate a phase transition, which is clearly confirmed by contrast between (0,0) and (0,1) absorption features and the bathoshift of (0,0) absorption peak corresponding to the temperature of the substrate. The enthalpy change on DSC curve suggests that the transition is one from low-ordered state to a higher-ordered state. A stacking mood that the 4-trifluoro- methyl-2,3,5,6-tetrafluorophenylmserts in between two perylene-macrocycles is confirmed by theoretical quantum calculation, such an insertion effect leads to the inversion of (0,0) and (0,1) absorption features under low temperature and the dramatic decrease of exciton coupling, which contributes to the spectral similarity in solution and the solid state. The transition fro amorphous to crystal state is ambiguously confirmed by the X-ray diffractionexperiment.SEM, TEM and XRD experiments suggested that; in comparison with ZnTPP, ZnFTPP was prone to form globular nanocrystallites and uniform and smooth films. The oxidation potential for ZnFTPP, which is 0.4 eV higher than that of ZnTPP, indicates its better stability to oxidation reagents. All these results are of fundamental significance to modern opto/electronic devices based organic thin films. |
