THE DIELECTRIC FUNCTION OF THE DIPHTHALOCYANINES OF RARE-EARTH-METALSAS A THIN-FILM MATERIAL

The diphthalocyanines of rare earth metals (LnPc(2)) with Pc = (C32H16 N8)(2-) and Ln is a trivalent metallic ion, are well-known for their e lectrochromic and semiconducting properties. So they are interesting f or use as active compounds in thin film devices. As the LnPc(2) appear s as a thin film material in this system, knowledge on the behaviour o f the dielectric function of LnPc(2) films is essential for understand ing their unique properties. We have determined the real and imaginary parts of the dielectric function of LnPc(2) materials in the photon e nergy range E = 0.5...4.0 eV by means of the transmittance (T) and ref lectance (R) spectroscopy. For that purpose, diphthalocyanines of Ho, Er, Tm, and Yb were sublimed on quartz substrates as well as on ITO su bstrates. The dielectric function of the material was calculated from the T- and R- data by minimizing an error function by the method of co njugated gradients.