Variable angle spectroscopic ellipsometry studies of oriented phthalocyanine films. II. Copper phthalocyanine

Abstract

Recent studies obtaining the anisotropic complex dielectric spectra of oriented metal-free phthalocyanine (H2Pc) films with variable angle spectroscopic ellipsometry (VASE) have been extended to similarly oriented copper phthalocyanine (CuPc) thin films. The CuPc films were vacuum vapor deposited onto sputter deposited copper substrates. Two classes of anisotropically oriented films with thicknesses on the order of 1000 Å were produced with the molecular stacking b-axis in either a ‘‘standing’’ or surface-parallel configuration by controlling the substrate temperature. Reflection absorption infrared spectroscopy and x-ray diffraction were used to verify the different orientations. VASE data were acquired over a 4000–8000 Å wavelength range in 100 Å steps, and 45°–79° incidence angle range in 2° steps. Three-dimensional plots of the ellipsometric parameters, Δ and Ψ, versus wavelength and incidence angle have different characteristic shapes for the two classes of oriented films, similar to H2Pc, leading to significant differences in the optical constant spectral solutions obtained with an isotropic film model. Knowing the high degree of uniaxial ordering in the two film classes, approximate solutions to the parallel and perpendicular optical constants taken with respect to the crystalline b axis can be extracted from the isotropic solutions using a two-dimensional Bruggeman effective medium approximation.