Effect of the deposition method and ageing in atmosphere on the optical properties of tetraphenylporphyrins (TPPs) films

In this work thin films of 5,10,15,20-tetraphenylporphyrin (H2TPP) and 5,10,15,20-tetrakis(4-methoxyphenyl)porpyhrin (H2TMPP)) were prepared by organic molecular beam deposition (OMBD). In addition, spin coating was applied as an alternative preparation technique for thin films of H2TPP to investigate the influence of the deposition method on the optical properties. The preservation of the molecular structure was proven by comparative Raman spectroscopy studies between films and powder. Modelling of the spectroscopic ellipsometry data yields a uniaxial anisotropy of the optical constants for the films of both molecules deposited by OMBD, which was used to determine the relative orientation of the molecules with respect to the substrate. The effect of the storage in air on the optical properties of the OMBD films was investigated using the example of H2TMPP. The molecular order in the films was found to decrease while the film roughness increased compared to samples stored in nitrogen. (C) 2021 Elsevier B.V. All rights reserved.