Structural Studies of Thermally Evaporated Thin Films of Copper Phthalocyanine

Thin films of the organic semiconductor copper phthalocyanine (CuPc) are deposited onto glass substrates maintained at room temperature, and their structures investigated using X-ray diffractometry and infrared light absorption. Films of thicknesses approximately 0.1 μm are preferentially oriented in the [001] direction. Further growth of thicker films has the effect of randomizing the orientation of the phthalocyanine crystallites, with structure mainly of the α-form. Prolonged heating at 240 °C produces a structural transformation of much of the material from the α- to the stable β-form, with the films preferentially oriented in the [201] direction. These structural changes are confirmed by infrared optical absorption analysis.