Fabrication of Various Ordered Films of Oxotitanium(IV) Phthalocyanine by Vacuum Deposition and Their Spectroscopic Behavior

Abstract

Different types of ordered solid films of oxotitanium(IV) phthalocyanine (OTiPc) were grown in 50−500 nm thickness by vacuum deposition onto such conventional substrates as metal- and ITO-coated glass and neat glass at a rate of ∼0.05 nm s-1. Under 10-3−10-4 Pa isotropic films with short-range molecular organization and preferential molecular orientation were grown on the substrates kept at ∼25 °C but ordered α (phase II) or β (phase I) crystal films on the substrates heated at 150 °C. The deposition onto surface-oxidized Al, Ti, and Cu/glass, ITO/glass, and neat glass at ∼25 or 150 °C selectively gave ordered isotropic or α-crystal films which have preferential molecular alignments with “standing” orientations of the molecular plane with respect to the substrate surface. On the other hand, another type of ordered isotropic or β-crystal films with preferential “lying” molecular orientations was formed by the deposition onto Au, Ag, and unoxidized Cu on glass at ∼25 or 150 °C. In the case of 150 °C-heated Pt/glass, the α-crystal film with “standing” molecular orientations was grown under 10-3−10-4 Pa, but another type of α-crystal film with “lying” orientations under 2.7 × 10-5 Pa. Scanning electron microscopic observations of the ordered crystalline films indicated that single-crystal-like domains are grown from the bottom to the top of the film and are densely packed to give monolithic morphologies with little grain boundary. Visible−near-IR absorption and fluorescence spectra of the ordered solid films were recorded, showing unique dependences on the molecular alignments involving anisotropic behavior in the polarized absorption spectra of the α-crystal films with different molecular alignments.

An Ultra Closely π‐Stacked Organic Semiconductor for High Performance Field‐Effect Transistors

“…More complicated XRD peaks appeared at 150°C, in which the diffraction peaks at 7.5°, 12.5°, 25.3°, and 28.6°were assigned to a-phase and the diffraction peak at 26.2°was belonged to b-phase. [18][19][20] It was further confirmed from the XRD results that the vacuum deposited films of TiOPc on pure Si/SiO 2 surface were in amorphous or in mixed-phases states, which were consistent with the UV-NIR results. Yonehara and Brinkmann et al [18][19][20] found surface modifications of substrates with organic thin layers exerted remarkable effects on the molecular alignment of vacuum deposited TiOPc films.…”

“…[18][19][20] It was further confirmed from the XRD results that the vacuum deposited films of TiOPc on pure Si/SiO 2 surface were in amorphous or in mixed-phases states, which were consistent with the UV-NIR results. Yonehara and Brinkmann et al [18][19][20] found surface modifications of substrates with organic thin layers exerted remarkable effects on the molecular alignment of vacuum deposited TiOPc films. A highly ordered a-TiOPc film with an "edgeon" molecular orientation was selectively grown on the surfaces of the gold substrate modified with a self-assembled monolayer of octadecanethiol.…”

“…4b), in which the molecular plane made an angle of 62°with respect to the substrates. [18,19] Moreover, the appearance of the second-order diffraction peak at 15.0°(d = 5.9 Å) further enhanced the high order of the vacuum deposited films. Hence, it was promising that high performance OFETs could be available based on the highly ordered vacuum deposited films with the "edge-on" molecular orientation because charge transport was along the p-stacking direction in this case.…”

“…At 90°C, a weak peak at 6.8°(d = 12.9 Å) and an intense peak at 7.5°(d = 11.8 Å) emerged, in which the former was attributed to the XRD signal of a specific amorphous phase of TiOPc and the latter corresponded to a-TiOPc. [18][19][20] At 120°C, the peaks at 26.2°and…”

“…The XRD patterns of TiOPc films deposited on OTSmodified Si/SiO 2 substrates at 90, 120, 150°C were displayed in Figure 3b. An intense peak at 7.5°(d = 11.8 Å) due to the diffraction from (010) plane of a-phase [18][19][20] was observed, especially for 150°C, indicating highly ordered a-phase films with the (010) lattice plane parallel to the substrate, i.e., TiOPc molecules preferentially stood on substrates with an "edge-on" style orientation (Fig. 4b), in which the molecular plane made an angle of 62°with respect to the substrates.…”