• Hagara, Jakub

Abstract

<jats:p>Many polymorphic crystal structures of copper phthalocyanine (CuPc) have been reported over the past few decades, but despite its manifold applicability, the structure of the frequently mentioned α polymorph remained unclear. The base-centered unit cell (space group <jats:italic>C</jats:italic>2/<jats:italic>c</jats:italic>) suggested in 1966 was ruled out in 2003 and was replaced by a primitive triclinic unit cell (space group <jats:italic>P</jats:italic><jats:overline>1</jats:overline>). This study proves unequivocally that both α structures coexist in vacuum-deposited CuPc thin films on native silicon oxide by reciprocal space mapping using synchrotron radiation in grazing incidence. The unit-cell parameters and the space group were determined by kinematic scattering theory and provide possible molecular arrangements within the unit cell of the <jats:italic>C</jats:italic>2/<jats:italic>c</jats:italic> structure by excluded-volume considerations. <jats:italic>In situ</jats:italic> X-ray diffraction experiments and <jats:italic>ex situ</jats:italic> atomic force microscopy complement the experimental data further and provide insight into the formation of a smooth thin film by a temperature-driven downward diffusion of CuPc molecules during growth.</jats:p>

Topics

• x-ray diffraction
• theory
• experiment
• thin film
• atomic force microscopy
• copper
• Silicon
• space group