Temperature and orientation study of cobalt phthalocyanine CoPc thin films deposited on silicon substrate as studied by micro-Raman scattering spectroscopy M. Szybowicz a, ⁎, W. Bała b , S. Dümecke c , K. Fabisiak b , K. Paprocki b , M. Drozdowski a a Faculty of Technical Physics, Poznan University of Technology, Nieszawska 13A, 60–965 Poznań, Poland b Institute of Physics, Kazimierz Wielki University, Weyssenhoff Sq. 1, 85–072 Bydgoszcz, Poland c Brandenburg University of Applied Science, Magdeburgerstraβe 50, 14770 Brandenburg/Havel, Germany abstract article info Article history: Received 2 November 2010 Received in revised form 19 July 2011 Accepted 21 July 2011 Available online 29 July 2011 Keywords: Phthalocyanine Thin films Raman spectroscopy Molecular orientation 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 A 1g and B 1g 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 D 4h to C 4v , 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. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Metallophthalocyanines (MPc) are p-type semiconductors which possess very interesting optical and electrical properties. Due to their low cost of production, high thermal and chemical stability, metallophthalocyanines, especially as thin films, can be applicable in many advanced technological devices [1–3]. Thin layers of metallophthalocyanines as well as their junctions with a number of organic and inorganic semiconductors or metals can be utilized for optoelectronic applications such as light-emitting diodes, photovol- taic cells, and organic field effect transistors. Moreover, the metal- lophthalocyanines are very useful as transporting and injection layers in optoelectronics devices [4,5]. For this reason the knowledge of their optical and electrical properties is very important. The nonlinear optical properties of these materials can take full advantage in optical limiting, optical communications, optical computing, harmonic generation and optical switching devices [6,7]. As it was mentioned earlier, due to these exceptional properties, metallophthalocyanine thin films have been recently intensively investigated, especially by using the optical methods such as absorption, ellipsometry and Raman spectroscopy [8–11]. The Raman spectroscopy can be a useful tool to study various intra- and intermolecular energy transfer processes. Unfortunately, a little attention has been paid to the temperature dependencies of vibrational Raman modes of MPc's thin layers. In order to improve device technology, the deposition technique must provide film with reproducible electrical and optical response characteristics. Thus, the detailed information on intrinsic centers or contaminants in metallophthalocyanine thin films, which can produce effective recombination, is required. In the case of cobalt phthalocy- anine (CoPc) thin films, the knowledge of the surface morphology and the preferred orientation of the crystallites is essential for their successful applications. In order to examine the molecular arrangement and crystallite orientation studies were performed of on vacuum-deposited films of CoPc on crystalline substrates [12,13]. Within the analysis of preferred orientation in CoPc layers, polymorphism of crystalline structure CoPc layers plays an important role [14]. The differences between them are as follow follows: (i) the tilt angle of the molecules within the columns and (ii) the mutual arrangement of the columns [15]. The preferred orientation is usually determined by sample preparation conditions such as type of substrate (amorphous or single crystalline), substrate temperature deposition rate, and quality of the substrate surface. Very important is also heating and cooling process of organic thin layers, which in many cases leads to changes in polymorphic forms and arrangement of structures. In most cases, the molecules of MPc (M = Cu, Zn, Mg and Co) take the form of the flat molecules with D 4h symmetry [16]. The heating process changes the polymorphic Thin Solid Films 520 (2011) 623–627 ⁎ Corresponding author. Tel.: + 48 616653170; fax: + 48 616653164. E-mail address: miroslaw.szybowicz@put.poznan.pl (M. Szybowicz). 0040-6090/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2011.07.051 Contents lists available at ScienceDirect Thin Solid Films journal homepage: www.elsevier.com/locate/tsf