Langmuir, Vol.18, No.20, 7557-7563, 2002
Vapor deposition of oxotitanium(IV) phthalocyanine on surface-modified substrates: Effects of organic surfaces on molecular alignment
Surface modifications of gold-on-glass substrates with organic thin layers exerted remarkable effects on the molecular alignment in the ordered solid films of oxotitanium(IV) phthalocyanine (OTiPc) grown by conventional vapor deposition (VD). While VD onto a gold-on-glass substrate heated at 150 degreesC gave a highly ordered phase I (beta-form) crystalline film with parallel molecular orientations, ordered phase II (alpha-form) crystalline films with an obliquely standing molecular arrangement were selectively grown on the surfaces of the substrate modified with 9-cycle Langmuir-Blodgett layers of OTiPc, a self-assembled monolayer of octadecanethiol, and a spin-coated thin film of polyimide. Moreover, VD of OTiPc onto a rubbed polyimide film gave an in-plane ordered phase II film in which obliquely standing OTiPc molecules are aligned with the molecular plane parallel to the rubbing direction. This film revealed high dichroic behavior in the p-polarized visible and IR absorption spectra. The substrate-surface effects are discussed in terms of initial formation of "director layers" by interactions of depositing molecules with the organic surfaces.