Structural and Optical Properties of In-Plane Ordered Metallo-Phthalocyanine Thin Films Formed on Sapphire by Organic Molecular Beam Deposition

Thin films of dibenzo [b, t] phthalocyaninato-Zn(II) (ZnDBPc) were grown by UHV molecular beam deposition on polished sapphire (1̄012) surfaces. The structural and optical properties of the ZnDBPc films were investigated by atomic force microscopy, X-ray diffraction, polarization spectroscopy, and optical third harmonic generation. The films showed in-plane ordering over the entire substrate. Equally spaced atomic step arrays were clearly observed on the polished sapphire (1̄012) surface. The ZnDBPc molecules stacked themselves to form molecular columns, and the stacking direction was parallel to the step direction, resulting in in-plane ordering of the ZnDBPc films. The ordered ZnDBPc film strongly promoted the ordering of a TiOPc thin film deposited on it. The third-order nonlinear optical susceptibility χ (3) of this ordered TiOPc/ZnDBPc double-layer film showed high anisotropy, and its maximum χ (3) value was 3.0×10 -10 esu.