Temperature and orientation study of cobalt phthalocyanine CoPc thin films deposited on silicon substrate as studied by micro-Raman scattering spectroscopy

A series of cobalt phthalocyanine (CoPc) thin films deposited on n-type silicon substrate were studied using micro-Raman spectroscopy. The CoPc thin layers have been deposited at room temperature by the quasi-molecular beam evaporation. The micro-Raman scattering spectra of CoPc thin films were investigated in the spectral range 550-1650 cm-1 using different excitation wavelengths (488 nm and 785 nm). Moreover, using surface mapping we also obtained information from polarized Raman spectra connected with polymorphic phase of CoPc layer before and after annealing procedure. The Raman modes A1g and B1g are connected with different polymorphic of metallophthalocyanine phases (α and β form) of CoPc thin films. During heating and cooling procedure the change of molecular symmetry, from D4h to C4v, has been revealed. The observed behavior of Raman spectra is probably connected with central atom ion (Co) position in molecular ring of metallophthalocyanine and its distortion from planarity. The obtained results showed also the influence of the annealing process on the ordering of the molecular structure of CoPc thin films deposited on n-type silicon substrate.