Monolayer alignment and optical properties of Langmuir-Blodgett CuttbPc films

The molecular alignment of Langmuir-Blodgett (LB) thin films fabricated on clean and Al-coated glass substrates was investigated by X-ray diffraction, atomic force microscopy, Fourier-transform infrared spectroscopy and electric susceptibility measurements. Ultrathin films of tetra-tert-butyl copper-phthalocyanine (CuttbPc) mixed with promoting stearic acid (SA) were deposited on the substrates by the LB method, forming up to 20 monolayers in a layer-by-layer manner. Molecular alignment was observed to begin beyond about 7 layers. The tilt angle of molecules on the substrates was about 49° and the third-order electric susceptibility of the LB films was measured as Χ⁽³⁾: Im Χ⁽³⁾ = -3.86 × 10^-7 esu at a wavelength of 620 nm using a z-scan method.