Preferred orientation of copper phthalocyanine thin films evaporated on amorphous substrates
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. Ottmar and M. Hanack Institut fu¨r Organische Chemie, Universita¨t Tu¨bingen, Tu¨bingen, Germany
J. Keckesb)
¨ sterreichische Akademie der Wissenschaften and Erich-Schmid-Institut fu¨r Materialwissenschaften, O Institut fu¨r Metallphysik, Montanuniversita¨t Leoben, Austria
G. Leising Institut fu¨r Festko¨rperphysik, Technische Universita¨t Graz, Petersgasse 16, A-8010 Graz, Austria (Received 12 July 1999; accepted 18 January 2000)
A series of copper phthalocyanine thin films were prepared on amorphous substrates using physical vapor deposition at ambient temperature. Different sample preparation conditions were used: the deposition rate was varied, and the substrates was static or rotating. The preferred orientation in the thin film was studied as a function of the deposition conditions. X-ray diffraction analysis was performed using /2 and pole figure measurements. In the case of layers prepared at low deposition rates and using nonrotating substrates, a very strong fiber texture was detected with (100) crystallographic planes oriented preferably parallel to the substrate surface. At higher deposition rates, an additional second type of preferred orientation was observed with (110) planes oriented preferably parallel to the substrate surface. In the case of layers prepared with rotational substrates, the (110) type of preferred orientation was quantitatively more strongly developed. If we consider electronic band structure calculations, these results imply that the electron/hole transport through the thin films is enhanced for films prepared at high deposition rates and rotating substrates.
I. INTRODUCTION
Phthalocyanines (Pc) represent a large family of heterocyclic conjugated molecules with high chemical and thermal stability.1 The outstanding optical and electrical properties of these materials open a wide variety of applications in modern opto-electronic devices:2 titanyl phthalocanine is used as charge generation material in laser printers and photocopy equipment.3 Other potential applications of Pc include optical recording, gas sensors, thin-film transistors, and solar cells.4 –7 Thin films of copper phthalocyanine (CuPc) are employed as hole injection layers in light emitting devices.8,9 Since the optical as well as the electrical properties of the molecular material are highly anisotropic, the orientation of CuPc within thin films is essential for successful application. Thin films of CuPc have been already studied extensively. Different orientations of CuPc molecules were obtained by epitaxial growth on a)
Address all correspondence to this author. e-mail: [email protected] b) Permanent address: Institute for Inorganic Chemistry, Slovak Academy of Sciences, SK-842 36 Bratislava, Slovakia. 934
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J. Mater. Res., Vol. 15, No. 4, Apr 2000 Downloaded: 15 Mar 2015
various substrates.10–14 Moreover, crystalline films with specific type of preferred orientation were prepared by special deposition techniques15–17 and also simply by physical vapor deposition on amo
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