The molecular structure ordering and orientation of the metallophthalocyanine CoPc, ZnPc, CuPc, and MgPc thin layers deposited on silicon substrate, as studied by micro-Raman spectroscopy

Abstract

In this article, we present orientation study of metallophthalocyanine (MPcs) (CoPc, ZnPc, CuPc, and MgPc) thin films deposited on silicon substrate. The MPc's thin layers were obtained by the quasi-molecular beam evaporation. The micro-Raman scattering spectra of MPc's thin films were investigated in the spectral range 550-1650 cm -1 using 488 nm excitation wavelength. Raman scattering studies were performed at room temperature before and after annealing process. Annealing process of thin layers was carried out at 200°C for 6 h. From polarized Raman spectra using surface Raman mapping, the information on polymorphic phase of MPc's layers has been obtained. The chosen Raman modes A 1g and B 1g are connected with different polymorphic phases of MPc (a and b form) thin layers. Moreover, the obtained results showed the influence of the annealing process on the ordering of the molecular structure. Following the annealing process, it was observed arrangement of the thin layers structure being revealed in Raman spectra. The obtained results indicate that the annealing process has a significant influence on the structure of thin layers being under study.

Probing the Effect of Molecular Orientation on the Intensity of Chemical Enhancement Using Graphene‐Enhanced Raman Spectroscopy

“…The former was known to decrease the Raman intensity, which indicated the latter enhanced it more remarkably since we observed the enhancement effect after annealing, as shown in Figure 2a. Note that when there is no other enhancement effect, annealing of the CuPc LB film will simply induce a decrease of the Raman intensity 37, 38. Therefore, we conclude here that the Raman intensity in GERS is very sensitive to the molecular orientation.…”

Orientation study of iron phthalocyanine (FePc) thin films deposited on silicon substrate investigated by atomic force microscopy and micro-Raman spectroscopy

“…However, in these cases, the thickness of the deposited layer was about 400 nm. As it is known, from our earlier study the increase of thickness leads to a change of the angle between molecule and substrate due to increasing of the layer-layer interaction and decreasing of the interaction process between layer and substrate [24]. The annealing process in most cases is leading to the formation of stable form of molecules (standing molecules).…”

“…So it can be useful as a marker for distinguishing a different metallophthalocyanine thin film. In our previous study, we recorded this band at 1,544 cm -1 for CoPc; 1,525 cm -1 for CuPc; 1,509 cm -1 for ZnPc, and 1,499 cm -1 for MgPc thin layers [24]. As it is known, the change of energy of this band is connected with the mass of the substituted metal atom in phthalocyanine molecule, metal ion size and cavity diameter of phthalocyanine [21].…”

“…The vibrations of the FePc planar molecules which consist of 57 atoms and possessing D 4h point group symmetry has been described in our previous article for CuPc, MgPc, and ZnPc can be classified into following irreducible representation (taking into account only internal vibrations) [22][23][24]:…”

“…In this configuration, the molecular z 0 -axis does not coincides with the normal to the surface (z-axis). Detailed information concerning the designation of the orientation of the metallophthalocyanine thin layers using polarized Raman spectra have been already reported in our previous articles [22,24]. The molecular orientation of FePc thin films was examined for two thicknesses of the thin layers equal to 79 and 230 nm.…”